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1.  Low doses of caffeine reduce heart rate during submaximal cycle ergometry 
Background
The purpose of this study was to examine the cardiovascular effects of two low-levels of caffeine ingestion in non habitual caffeine users at various submaximal and maximal exercise intensities.
Methods
Nine male subjects (19–25 yr; 83.3 ± 3.1 kg; 184 ± 2 cm), underwent three testing sessions administered in a randomized and double-blind fashion. During each session, subjects were provided 4 oz of water and a gelatin capsule containing a placebo, 1.5 mg/kg caffeine, or 3.0 mg/kg caffeine. After thirty minutes of rest, a warm-up (30 Watts for 2 min) the pedal rate of 60 rpm was maintained at a steady-state output of 60 watts for five minutes; increased to 120 watts for five minutes and to 180 watts for five minutes. After a 2 min rest the workload was 180 watts for one minute and increased by 30 watts every minute until exhaustion. Heart rate (HR) was measured during the last 15-seconds of each minute of submaximal exercise. Systolic blood pressure (BP) was measured at rest and during each of the three sub-maximal steady state power outputs. Minute ventilation (VE), Tidal volume (VT), Breathing frequency (Bf), Rating of perceived exertion (RPE), Respiratory exchange ratio (RER), and Oxygen consumption (VO2) were measured at rest and during each minute of exercise.
Results
Caffeine at 1.5 and 3.0 mg/kg body weight significantly lowered (p < 0.05) HR during all three submaximal exercise intensities compared to placebo (range – 4 to 7 bpm lower) but not at rest or maximal exercise. BP was significantly higher (p < 0.05) at rest and after the 3 mg/kg caffeine vs placebo (116 ± 13 vs 123 ± 10 mm Hg). Neither dose of caffeine had any effect on BP during submaximal exercise. Caffeine had no effect on VE, VT, VO2, RPE, maximal power output or time to exhaustion.
Conclusion
In non habitual caffeine users it appears that consuming a caffeine pill (1.5 & 3.0 mg/kg) at a dose comparable to 1–3 cups of coffee lowers heart rate during submaximal exercise but not at near maximal and maximal exercise. In addition, this caffeine dose also only appears to affect systolic blood pressure at rest but not during cycling exercise.
doi:10.1186/1550-2783-4-11
PMCID: PMC2164943  PMID: 17925021
2.  THE INFLUENCE OF OBESITY AND AMBIENT TEMPERATURE ON PHYSIOLOGICAL AND OXIDATIVE RESPONSES TO SUBMAXIMAL EXERCISE 
Biology of Sport  2014;31(2):139-144.
This study investigated the effects of obesity and ambient temperature on physiological responses and markers of oxidative stress to submaximal exercise in obese and lean people. Sixteen healthy males were divided into an obese group (n=8, %fat: 27.00±3.00%) and a lean group (n=8, %fat: 13.85±2.45%). Study variables were measured during a 60 min submaximal exercise test at 60% VO2max in a neutral (21±1°C) and a cold (4±1°C) environment. Heart rate, blood lactate, rectal temperature, serum levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were measured at rest, during exercise and in recovery. Heart rate of both groups was significantly lower (P<0.05) in the cold than the warm environment, but there were no significant differences between the two groups. Serum SOD activity increased to a significantly greater extent (P<0.05) in the cold than the neutral environment, and remained elevated for longer during exercise in the obese group than the lean group. Serum MDA level during submaximal exercise was not significantly different between conditions or groups. Cold stress in exercise may challenge antioxidant defence mechanisms in obese subjects, but lipid peroxidation remains unchanged.
doi:10.5604/20831862.1097482
PMCID: PMC4042661  PMID: 24899779
oxidative stress; cold; obese; physiological response; exercise
3.  Randomised, controlled walking trials in postmenopausal women: the minimum dose to improve aerobic fitness? 
Background: The American College of Sports Medicine recommends 20–60 minutes of aerobic exercise three to five days a week at an intensity of 40/50–85% of maximal aerobic power (VO2MAX) reserve, expending a total of 700–2000 kcal (2.93–8.36 MJ) a week to improve aerobic power and body composition.
Objective: To ascertain the minimum effective dose of exercise.
Methods: Voluntary, healthy, non-obese, sedentary, postmenopausal women (n = 121), 48–63 years of age, were randomised to four low dose walking groups or a control group; 116 subjects completed the study. The exercise groups walked five days a week for 24 weeks with the following intensity (% of VO2MAX) and energy expenditure (kcal/week): group W1, 55%/1500 kcal; group W2, 45%/1500 kcal; group W3, 55%/1000 kcal; group W4, 45%/1000 kcal. VO2MAX was measured in a direct maximal treadmill test. Submaximal aerobic fitness was estimated as heart rates at submaximal work levels corresponding to 65% and 75% of the baseline VO2MAX. The body mass index (BMI) was calculated and percentage of body fat (F%) estimated from skinfolds.
Results: The net change (the differences between changes in each exercise group and the control group) in VO2MAX was 2.9 ml/min/kg (95% confidence interval (CI) 1.5 to 4.2) in group W1, 2.6 ml/min/kg (95% CI 1.3 to 4.0) in group W2, 2.4 ml/min/kg (95% CI 0.9 to 3.8) in group W3, and 2.2 ml/min/kg (95% CI 0.8 to 3.5) in group W4. The heart rates in standard submaximal work decreased 4 to 8 beats/min in all the groups. There was no change in BMI, but the F% decreased by about 1% unit in all the groups.
Conclusions: Walking (for 24 weeks) at moderate intensity 45% to 55% of VO2MAX, with a total weekly energy expenditure of 1000–1500 kcal, improves VO2MAX and body composition of previously sedentary, non-obese, postmenopausal women. This dose of exercise apparently approaches the minimum effective dose.
doi:10.1136/bjsm.36.3.189
PMCID: PMC1724503  PMID: 12055113
4.  Plasma adipokine and inflammatory marker concentrations are altered in obese, as opposed to non-obese, type 2 diabetes patients 
Elevated plasma free fatty acid (FFA), inflammatory marker, and altered adipokine concentrations have been observed in obese type 2 diabetes patients. It remains unclear whether these altered plasma concentrations are related to the diabetic state or presence of obesity. In this cross-sectional observational study, we compare basal plasma FFA, inflammatory marker, and adipokine concentrations between obese and non-obese type 2 diabetes patients and healthy, non-obese controls. A total of 20 healthy, normoglycemic males (BMI <30 kg/m2), 20 non-obese (BMI <30 kg/m2) and 20 obese (BMI >35 kg/m2) type 2 diabetes patients were selected to participate in this study. Groups were matched for age and habitual physical activity level. Body composition, glycemic control, and exercise performance capacity were assessed. Basal blood samples were collected to determine plasma leptin, adiponectin, resistin, tumor necrosis factor α (TNFα), interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP) and FFA concentrations. Plasma FFA, inflammatory marker (hsCRP, IL-6, TNFα), adipokine (adiponectin, resistin, leptin), and triglyceride concentrations did not differ between non-obese diabetes patients and healthy, normoglycemic controls. Plasma FFA, IL-6, hsCRP, leptin, and triglyceride levels were significantly higher in the obese diabetes patients when compared with the healthy normoglycemic controls (P < 0.05). Furthermore, plasma hsCRP and leptin levels were significantly higher in the obese versus non-obese diabetes patients (P < 0.05). Significant correlations between plasma parameters and glycemic control were observed, but disappeared after adjusting for trunk adipose tissue mass. Elevated plasma leptin, hsCRP, IL-6, and FFA concentrations are associated with obesity and not necessarily with the type 2 diabetic state.
doi:10.1007/s00421-010-1362-5
PMCID: PMC2874484  PMID: 20131064
Obesity; Diabetes; Adipokines; Inflammation; Fat mass
5.  Comparison of Active and Electrostimulated Recovery Strategies After Fatiguing Exercise 
The purpose of this study was to compare an electrostimulated to an active recovery strategy after a submaximal isometric fatiguing exercise. Nineteen healthy men completed three sessions (separated by at least 4 weeks) which included a knee extensors provocation exercise consisting of 3 sets of 25 isometric contractions. Contraction intensity level was fixed respectively at 60%, 55% and 50% of previously determined maximal voluntary contraction for the first, second and third sets. This provocation exercise was followed by either an active (AR) recovery (25 min pedaling on a cycle ergometer), an electrostimulated (ESR) recovery (25-min continuous and non-tetanic (5 Hz) stimulation of the quadriceps) or a strictly passive recovery (PR). Peak torques of knee extensors and subjective perception of muscle pain (VAS, 0-10) were evaluated before (pre-ex), immediately after the provocation exercise (post-ex), after the recovery period (post-rec), as well as 75 minutes (1h15) and one day (24h) after the exercise bout. Time course of peak torque was similar among the different recovery modes: ~ 75% of initial values at post-ex, ~ 90% at post-rec and at 1h15. At 24h, peak torque reached a level close to baseline values (PR: 99.1 ± 10.7%, AR: 105.3 ± 12.2%, ESR: 104.4 ± 10.5%). VAS muscle pain scores decreased rapidly between post-ex and post-rec (p < 0.001); there were no significant differences between the three recovery modes (p = 0.64). In conclusion, following a submaximal isometric knee extension exercise, neither electrostimulated nor active recovery strategies significantly improved the time course of muscle function recovery.
Key pointsThree sets of submaximal isometric contractions at 60%, 55% and 50% of MVC induced an early fatigue without DOMS but did not lead to exhaustion.In comparison with passive recovery, active and electrostimulated recovery did not lead to significantly higher MVC torques 24h after the exercise bout.No significant differences were demonstrated between the effects of passive, active and electrostimulated recoveries on muscle pain after repeated submaximal isometric contractions.
PMCID: PMC3761726  PMID: 24149681
Electrical stimulation; muscle recovery; isometric contraction; muscle fatigue
6.  Effect of a twelve week exercise programme on cardio-respiratory and body composition variables in non-obese young and middle-aged females 
This study investigated the effect of a 12-week exercise programme consisting of jogging, calistnenics, and recreational activities on the cardiorespiratory function and body composition of 15 young and 15 middle-aged nonobese women 21-32 and 34-57 years, respectively. The exercise programme was 3 days per week for an average of 45 minutes each session. Pre- and post-programme data were obtained on: age, height, total body weight, resting heart rate, systolic and diastolic blood pressure, vital capacity, submaximal heart rate, supra-iliac skinfold, thigh skinfold, waist girth, cup size, body density, and percent fat. The t-test was used to test the difference between the young and middle-aged groups before and after the exercise programme and to test the pre- and post-programme mean values of each group. No differences between the groups or changes due to the exercise programme were observed on total body weight. No significant cardiorespiratory differences were found between the two groups at either test period, however, the young group decreased significantly (p < .01) in submaximal HR and the middle-aged group decreased significantly in resting (p < .01) and submaximal (p < .001) HR illustrating the positive effect of the programme. No significant body composition differences were found between the two groups at the pre-test. At the post-test the middle-aged group had a significantly (p < .10) larger thigh skinfold thickness than the young group. The young group did not change significantly on body composition measures from pre- to post-test. In contrast, the middle-aged group increased significantly in body density (p < .01) and decreased in percent body fat (p < .01) due to a significant (p < .01) reduction in supra-iliac skinfold thickness from 21.67 ± 2.35 to 18.13 ± 2.08 mm. The data were compared with data from other studies using similar age groups. The pre-test percent fat of the young group (25.07 ± .74) was similar to values reported in other studies. The middle-aged group had a relatively lower fat percentage (27.46 ± 1.58) compared with other middle-aged groups.
PMCID: PMC1859622  PMID: 630177
7.  Mechanical and Magnetic Resonance Imaging Changes Following Eccentric or Concentric Exertions 
Background
Prior work has shown that changes in mechanical parameters and magnetic resonance imaging (MRI) parameters occur following submaximal eccentric activity but it is unclear whether similar changes occur following submaximal concentric activity. This study compared mechanical response parameters and MRI relaxation parameters following submaximal concentric or eccentric exertions.
Methods
This single site, randomized study investigated in-vivo changes in human upper limb dynamic mechanical properties following exposure to short term repetitive submaximal eccentric or concentric exertions. Eighteen subjects were assigned to either an eccentric or concentric group and exercised for 30 minutes at 50% of isometric forearm maximum voluntary contraction. Changes in strength, symptom intensity, MRI T2 relaxation measurements, which are indicative of edema, and dynamic mechanical parameters (stiffness, effective mass, and damping) were ascertained prior to exercise, one hour after, and 24 hours later.
Findings
Strength decreased following exercise (P < 0.01), however only the eccentric exercise group exhibited a reduction in mechanical stiffness (55%, P <0.01) and damping (31%, P < 0.05), and an increase (17%, P < 0.05) in MRI T2 relaxation time.
Interpretations
The changes in mechanical parameters and MRI findings following repetitive submaximal eccentric activity could negatively impact the ability of the arm to react to rapid forceful loading during repetitive industrial work activities and may result in increased strain on the upper limb. Similar changes were not observed following concentric exercise.
doi:10.1016/j.clinbiomech.2008.03.068
PMCID: PMC2581652  PMID: 18485551
Mechanical parameters; stiffness; forearm; submaximal eccentric exertions; MRI
8.  Plasma levels of soluble tumor necrosis factor-α receptors are related to total and LDL-cholesterol in lean, but not in obese subjects 
Background
Tumor necrosis factor-α (TNFα) is a mediator of insulin resistance. Plasma levels of soluble TNFα receptors (sTNFR1 and sTNFR2) probably reflect paracrine action of the cytokine. TNFα is also a regulator of lipid metabolism, however, data about impact of obesity on the relationships between TNFα and plasma lipids remain controversial.
Aim
The purpose of the present study was to examine the associations of TNFα system with plasma lipids in lean and obese subjects with normal glucose metabolism.
Methods
We examined 63 subjects, 33 lean (BMI<25 kg × m-2) and 30 with marked overweight or obesity (BMI>27.8 kg × m-2). Anthropometric and biochemical parameters were measured. Oral glucose tolerance test and euglycemic hyperinsulinemic clamp were also performed.
Results
Obese subjects were markedly more insulin resistant and had higher levels of both TNFα receptors. Total (TC) and LDL-cholesterol (LDL-C), triglycerides (TG) and non-esterified fatty acids (NEFA) were also higher in the obese group. In obese subjects, both receptors were significantly related to TG and HDL-cholesterol (HDL-C), while sTNFR2 was also associated with NEFA. All those correlations disappeared after controlling for insulin sensitivity. In lean subjects, both receptors were related to TC, HDL-C and LDL-C. In that group, sTNFR1 predicted values of all those parameters independently of BMI, plasma glucose and insulin, and insulin sensitivity.
Conclusion
We conclude that TNFα receptors are associated with plasma lipids in different way in lean and in obese subjects. TNFα system is probably important in determining cholesterol levels in lean subjects, while in obese this effect might be masked by other metabolic abnormalities.
doi:10.1186/1475-2840-5-14
PMCID: PMC1524944  PMID: 16803616
9.  Substrate utilization during submaximal exercise in children with a severely obese parent 
Background
We have reported a reduction in fatty acid oxidation (FAO) at the whole-body level and in skeletal muscle in severely obese (BMI ≥ 40 kg/m2) individuals; this defect is retained in cell culture suggesting an inherent component. The purpose of the current study was to determine if an impairment in whole-body fatty acid oxidation (FAO) was also evident in children with a severely obese parent.
Methods
Substrate utilization during submaximal exercise (cycle ergometer) was determined in children ages 8–12 y with a severely obese parent (OP, n = 13) or two lean/non-obese (BMI range of 18 to 28 kg/m2) parents (LP, n = 13). A subgroup of subjects (n = 3/group) performed 4 weeks of exercise training with substrate utilization measured after the intervention.
Results
The children did not differ in age (LP vs. OP, respectively) (10.7 ± 0.5 vs. 10.2 ± 0.5 y), BMI percentile (65.3 ± 5.2 vs. 75.9 ± 7), Tanner Stage (1.4 ± 0.2 vs. 1.5 ± 0.2), VO2peak (40.3 ± 2.7 vs. 35.6 ± 2.6 ml/kg/min) or physical activity levels (accelerometer). At the same absolute workload of 15 W (~38% VO2peak), RER was significantly (P ≤ 0.05) lower in LP vs. OP (0.83 ± 0.02 vs. 0.87 ± 0.01) which was reflected in a reduced reliance on FAO for energy production in the OP group (58.6 ± 5.1 vs. 43.1 ± 4.0% of energy needs during exercise from FAO). At a higher exercise intensity (~65% VO2peak) there were no differences in substrate utilization between LP and OP. After exercise training RER tended to decrease (P = 0.06) at the 15 W workload, suggesting an increased reliance on FAO regardless of group.
Conclusions
These findings suggest that the decrement in FAO with severe obesity has an inherent component that may be overcome with exercise training.
doi:10.1186/1743-7075-9-38
PMCID: PMC3422990  PMID: 22571243
Bariatric surgery; Class III obesity; Exercise; Fat oxidation; Skeletal muscle
10.  The Effect of Submaximal Exercise Preceded by Single Whole-Body Cryotherapy on the Markers of Oxidative Stress and Inflammation in Blood of Volleyball Players 
The aim of the study was to determine the effect of single whole-body cryotherapy (WBC) session applied prior to submaximal exercise on the activity of antioxidant enzymes, the concentration of lipid peroxidation products, total oxidative status, and the level of cytokines in blood of volleyball players. The study group consisted of 18 male professional volleyball players, who were subjected to extremely cold air (−130°C) prior to exercise performed on cycloergometer. Blood samples were taken five times: before WBC, after WBC procedure, after exercise preceded by cryotherapy (WBC exercise), and before and after exercise without WBC (control exercise). The activity of catalase statistically significantly increased after control exercise. Moreover, the activity of catalase and superoxide dismutase was lower after WBC exercise than after control exercise (P < 0.001). After WBC exercise, the level of IL-6 and IL-1β was also lower (P < 0.001) than after control exercise. The obtained results may suggest that cryotherapy prior to exercise may have some antioxidant and anti-inflammatory properties. The relations between the level of studied oxidative stress and inflammatory markers may testify to the contribution of reactive oxygen species in cytokines release into the blood system in response to exercise and WBC.
doi:10.1155/2013/409567
PMCID: PMC3893756  PMID: 24489985
11.  Physical Exercise Reduces the Expression of RANTES and Its CCR5 Receptor in the Adipose Tissue of Obese Humans 
Mediators of Inflammation  2014;2014:627150.
RANTES and its CCR5 receptor trigger inflammation and its progression to insulin resistance in obese. In the present study, we investigated for the first time the effect of physical exercise on the expression of RANTES and CCR5 in obese humans. Fifty-seven adult nondiabetic subjects (17 lean and 40 obese) were enrolled in a 3-month supervised physical exercise. RANTES and CCR5 expressions were measured in PBMCs and subcutaneous adipose tissue before and after exercise. Circulating plasma levels of RANTES were also investigated. There was a significant increase in RANTES and CCR5 expression in the subcutaneous adipose tissue of obese compared to lean. In PBMCs, however, while the levels of RANTES mRNA and protein were comparable between both groups, CCR5 mRNA was downregulated in obese subjects (P < 0.05). Physical exercise significantly reduced the expression of both RANTES and CCR5 (P < 0.05) in the adipose tissue of obese individuals with a concomitant decrease in the levels of the inflammatory markers TNF-α, IL-6, and P-JNK. Circulating RANTES correlated negatively with anti-inflammatory IL-1ra (P = 0.001) and positively with proinflammatory IP-10 and TBARS levels (P < 0.05). Therefore, physical exercise may provide an effective approach for combating the deleterious effects associated with obesity through RANTES signaling in the adipose tissue.
doi:10.1155/2014/627150
PMCID: PMC4016945  PMID: 24895488
12.  Focal cerebral ischemia in the TNFalpha-transgenic rat 
Background
To determine if chronic elevation of the inflammatory cytokine, tumor necrosis factor-α (TNFα), will affect infarct volume or cortical perfusion after focal cerebral ischemia.
Methods
Transgenic (TNFα-Tg) rats overexpressing the murine TNFα gene in brain were prepared by injection of mouse DNA into rat oocytes. Brain levels of TNFα mRNA and protein were measured and compared between TNFα-Tg and non-transgenic (non-Tg) littermates. Mean infarct volume was calculated 24 hours or 7 days after one hour of reversible middle cerebral artery occlusion (MCAO). Cortical perfusion was monitored by laser-Doppler flowmetry (LDF) during MCAO. Cortical vascular density was quantified by stereology. Post-ischemic cell death was assessed by immunohistochemistry and regional measurement of caspase-3 activity or DNA fragmentation. Unpaired t tests or analysis of variance with post hoc tests were used for comparison of group means.
Results
In TNFα-Tg rat brain, the aggregate mouse and rat TNFα mRNA level was fourfold higher than in non-Tg littermates and the corresponding TNFα protein level was increased fivefold (p ≤ 0.01). Infarct volume was greater in TNFα-Tg rats than in non-Tg controls at 24 hours (p ≤ 0.05) and 7 days (p ≤ 0.01). Within the first 10 minutes of MCAO, cortical perfusion measured by LDF was reduced in TNFα-Tg rats (p ≤ 0.05). However, regional vascular density was equivalent between TNFα-Tg and non-Tg animals (p = NS). Neural cellular apoptosis was increased in transgenic animals as shown by elevated caspase-3 activity (p ≤ 0.05) and DNA fragmentation (p ≤ 0.001) at 24 hours.
Conclusion
Chronic elevation of TNFα protein in brain increases susceptibility to ischemic injury but has no effect on vascular density. TNFα-Tg animals are more susceptible to apoptotic cell death after MCAO than are non-Tg animals. We conclude that the TNFα-Tg rat is a valuable new tool for the study of cytokine-mediated ischemic brain injury.
doi:10.1186/1742-2094-5-47
PMCID: PMC2583993  PMID: 18947406
13.  Weight loss and exercise training effect on oxygen uptake and heart rate response to locomotion 
Effects of resistance and aerobic training on ease of physical activity during and following weight loss are unknown. Purpose of study is to determine what affect weight loss combined with either aerobic or resistance training has on ease of locomotion (netVO2 and heart rate). It is hypothesized that exercise training will result in increased ease, lower heart rate during locomotion. Seventy three overweight, premenopausal women were assigned to diet and aerobic training, diet and resistance training, or diet only. Subjects were evaluated while overweight, after diet induced weight loss (average 12.5 kg loss), and one year following weight loss (5.5 kg regain). Submaximal walking, grade walking, stair climbing, and bike oxygen uptake and heart rate were measured at all time points. Weight loss diet was 800 kcal/day. Exercisers trained 3 times/wk during weight loss and 2 times/wk during one year follow-up. Resistance training increased strength and aerobic training increased maximum oxygen uptake. Net submaximal oxygen uptake was not affected by weight loss or exercise training. However, heart rate during walking, stair climbing, and bicycling was reduced following weight loss. No significant differences in reduction in heart rate were observed between the 3 treatment groups for locomotion following weight loss. However, during one-year follow-up, exercise training resulted in maintenance of lower submaximal heart rate, while non exercisers increased heart rate during locomotion. Results, suggest that moderately intense exercise is helpful in improving ease of movement following weight loss. Exercise training may be helpful in increasing participation in free living physical activity.
doi:10.1519/JSC.0b013e31824f236c
PMCID: PMC3664274  PMID: 22344063
Aerobic training; Resistance training; calorie restriction
14.  The effect of minimal exercise on fitness in elderly women after hip surgery. 
The Ulster Medical Journal  1995;64(2):118-125.
To determine the effect of minimal exercise on functional fitness following total hip replacement in elderly women, 20 women (13 exercisers, 7 controls) who had undergone unilateral or bilateral hip replacement surgery for primary osteoarthritis were studied. An exercise treadmill test with respiratory gas and blood lactate analyses, and a field test of walking speed on a measured course, were administered before and after a twice weekly exercise programme of three months' duration. Markers of cardiorespiratory fitness, including peak achieved oxygen uptake (VO2) and ventilatory and lactate thresholds were measured. Maximum self-selected walking speed was also measured over a flat course. Peak VO2 increased in the exercise group when compared to baseline (P < 0.05) but did not differ from the control group. The exercise group significantly improved their walking speed by 10.1% compared with non-exercising controls (1.41 vs 1.20 m/sec, P < 0.05), and increased VO2 at lactate threshold. The improvements occurred despite the twice weekly exercise sessions being below the recommended frequency of exercise for improving cardiorespiratory fitness. Minimal exercise in elderly women after hip surgery can substantially improve submaximal exercise capacity, as well as walking speed.
PMCID: PMC2448534  PMID: 8533175
15.  Cryotherapy, Sensation, and Isometric-Force Variability 
Journal of Athletic Training  2003;38(2):113-119.
Objective:
To determine the changes in sensation of pressure, 2-point discrimination, and submaximal isometric-force production variability due to cryotherapy.
Design and Setting:
Sensation was assessed using a 2 × 2 × 2 × 3 repeated-measures factorial design, with treatment (ice immersion or control), limb (right or left), digit (finger or thumb), and sensation test time (baseline, posttreatment, or postisometric-force trials) as independent variables. Dependent variables were changes in sensation of pressure and 2-point discrimination. Isometric-force variability was tested with a 2 × 2 × 3 repeated-measures factorial design. Treatment condition (ice immersion or control), limb (right or left), and percentage (10, 25, or 40) of maximal voluntary isometric contraction (MVIC) were the independent variables. The dependent variables were the precision or variability (the standard deviation of mean isometric force) and the accuracy or targeting error (the root mean square error) of the isometric force for each percentage of MVIC.
Subjects:
Fifteen volunteer college students (8 men, 7 women; age = 22 ± 3 years; mass = 72 ± 21.9 kg; height = 183.4 ± 11.6 cm).
Measurements:
We measured sensation in the distal palmar aspect of the index finger and thumb. Sensation of pressure and 2-point discrimination were measured before treatment (baseline), after treatment (15 minutes of ice immersion or control), and at the completion of isometric testing (final). Variability (standard deviation of mean isometric force) of the submaximal isometric finger forces was measured by having the subjects exert a pinching force with the thumb and index finger for 30 seconds. Subjects performed the pinching task at the 3 submaximal levels of MVIC (10%, 25%, and 40%), with the order of trials assigned randomly. The subjects were given a target representing the submaximal percentage of MVIC and visual feedback of the force produced as they pinched the testing device. The force exerted was measured using strain gauges mounted on an apparatus built to measure finger forces.
Results:
Sensation of pressure was less (ie, it took greater pressure to elicit a response) after ice immersion, thumbs were more affected than index fingers, and the decrease was greater in the right limb than the left. Two-point discrimination was not affected by cryotherapy but was higher in the finger than in the thumb under all conditions. Isometric-force variability (standard deviation of mean isometric force) was greater as percentage of force increased from 10% to 40% of MVIC. Targeting accuracy (root mean square error) was decreased at 40% of MVIC. Accuracy and force variability were not affected by cryotherapy.
Conclusions:
The application of cryotherapy and reduced sensation of pressure appear to have little effect on motor control of the digits. These results support the hypothesis that the use of cold is not contraindicated for use as an analgesic before submaximal rehabilitative exercise focusing on restoring neuromuscular control to injured tissues.
PMCID: PMC164899  PMID: 12937521
root mean square error; accuracy; precision; sensation; maximal voluntary isometric contraction
16.  Responses of young girls to two modes of aerobic training. 
OBJECTIVES: To investigate the physiological effects of two different three times a week, eight week training programmes on the aerobic fitness of nine to ten year old girls. METHODS: Treadmill determined peak VO2, submaximal heart rates, and submaximal blood lactate were the criterion measures. Seventeen girls completed a programme of "aerobics" training where sessions lasted 20-25 minutes. Eighteen girls followed a cycle ergometer training programme which involved pedalling continuously for 20 minutes with the heart rate maintained between 160 and 170 beats/minute. A control group of 16 girls completed the criterion tests but did not train. In the cycle ergometer group and eight control subjects plasma total cholesterol and high density lipoprotein cholesterol were determined before and after training. RESULTS: Peak VO2 did not change significantly with training in either training group, neither were there any significant changes in submaximal heart rates. Blood lactate declined significantly at the two lowest submaximal exercise intensities in the cycle ergometer training group (from 2.3 (1.1) to 1.4 (0.06) mmol/l at stage 1 and from 2.1 (1.2) to 1.6 (0.06) mmol/l at stage 2; means (SD); P < 0.01). Total cholesterol and high density lipoprotein cholesterol remained unchanged with training. CONCLUSIONS: These findings suggest that an eight week structured exercise programme produces minimal changes in either the aerobic fitness or blood lipids of young girls. It may be more beneficial for long term health to promote enjoyment in activity and positive attitudes to exercise rather than attempting to enhance aerobic fitness through strenuous exercise programmes.
PMCID: PMC1332614  PMID: 9192129
17.  Evaluation of immune response after moderate and overtraining exercise in wistar rat 
Objective(s): The effect of prolonged overtraining on cytokine kinetics was compared with moderate exercise in the present study.
Materials and Methods: Male Wistar rats were randomly divided into control sedentary (C), moderate trained (MT), (V=20 m/min, 30 min/day for 6 days a week, 8 weeks), overtrained (OT) (V=25 m/min, 60min/day for 6 days a week, 11 weeks) and recovered overtrained (OR) (OT plus 2 weeks recovery) groups, (n=6 for each group). Immediately, 24 hr and 2 weeks (in OR) after last bout of exercise blood samples were obtained. The plasma concentrations of TNFα, IL-6, IL-10, IL-4 and IFN were measured by ELISA method.
Results: Immediately after last bout of exercise the following findings were observed; IL-6, IL-10 and TNFα concentrations increased in OT and OR groups compared with control (P<0.05–P<0.001). Serum level of IL-4 decreased (P<0.01) but IFN increased (P<0.05) in MT group vs. control. In addition, circulatory levels of TNFα, IL-6, IL-10 and IL-4 were higher but the IFN concentrations were lower in OT and OR groups than MT group (P<0.05-P<0.01). The IFN-γ/IL4 ratio was significantly increased in MT (P<0.01) while it decreased in OT group. There were not statistical differences in TNFα, IL-6, and IFN levels between different time intervals after exercise in MT, OT and OR groups.
Conclusion: These data confirm a positive effect of moderate exercise on immune function and a decrease in susceptibility to viral infection by inducing Th1 cytokine profile shift. However, prolonged and overtraining exercise causes numerous changes in immunity that possibly reflects physiological stress and immune suppression.
PMCID: PMC3938879  PMID: 24592300
Immune system; Moderate exercise; Overtraining exercise; Rat; Th1; Th2
18.  Inspiratory Muscle Fatigue Following Moderate-Intensity Exercise in the Heat 
Heavy exercise has been shown to elicit reductions in inspiratory muscle strength in healthy subjects. Our purpose was to determine the combined effects of moderate-intensity endurance exercise and a thermal load on inspiratory muscle strength in active subjects. Eight active, non heat-acclimatized female subjects (23.5 ± 1.4 yr; VO2max = 39.8 ± 2.4 ml.kg-1.min-1) randomly performed two 40 min endurance exercise bouts (60% VO2max) in either a thermo-neutral (22°C/21% RH) or hot (37°C/33% RH) environment on separate days. Maximal sustained inspiratory mouth pressure (PImax) was obtained pre and post exercise as an index of inspiratory muscle strength. Additional variables obtained every 10 min during the endurance exercise bouts included: rectal temperature (TRE), heart rate (HR), minute ventilation (VE), oxygen uptake (VO2), tidal volume (VT), breathing frequency (Fb), and ratings of perceived exertion and dyspnea (RPE/RPD). Data were analyzed with repeated measures ANOVA. PImax was significantly reduced (p < 0.05) after exercise in the hot environment when compared to baseline and when compared to post exercise values in the thermo-neutral environment. PImax was unchanged from baseline following exercise in the thermo-neutral environment. HR and TRE were significantly higher (p < 0.05) in the hot compared to the thermo-neutral environment. VE and VO2 were not significantly different between conditions. VT was unchanged between conditions whereas Fb was higher (p < 0.05) in the hot condition compared to thermo-neutral. RPE was not significantly different between conditions. RPD was significantly higher (p < 0.05) in the hot compared to the thermo-neutral environment. We conclude that moderate-intensity endurance exercise (60% VO2max) in a hot environment elicits significant reductions in inspiratory muscle strength in unfit females. This finding is novel in that previous studies conducted in a thermo-neutral environment have shown that an exercise intensity of >80% VO2max is required to elicit reductions in inspiratory muscle strength. In addition, dyspnea perception during exercise is greater in a hot environment, compared to thermo-neutral, at a similar level of VE and VO2.
Key PointsThe combined effects of a heat load and exercise on inspiratory muscle strength were investigated in untrained female subjects.Previous studies have shown that a very high exercise intensity (> 80% VO2max) is required to elicit reductions in inspiratory muscle strength.Prolonged submaximal exercise (40-min/60% VO2max) in a hot environment significantly reduced inspiratory muscle strength in untrained females whereas the same intensity in a thermo-neutral environment had no effect on inspiratory muscle function.These reductions in inspiratory muscle strength may be related to competition for blood flow among the locomotor, inspiratory, and cutaneous circulations.
PMCID: PMC3887326  PMID: 24453527
Control of breathing; endurance; respiratory function; thermal load
19.  Effects of tiotropium on sympathetic activation during exercise in stable chronic obstructive pulmonary disease patients 
Background
Tiotropium partially relieves exertional dyspnea and reduces the risk of congestive heart failure in chronic obstructive pulmonary disease (COPD) patients. However, its effect on the sympathetic activation response to exercise is unknown.
Aims
This study aimed to determine whether tiotropium use results in a sustained reduction in sympathetic activation during exercise.
Methods
We conducted a 12-week, open-label (treatments: tiotropium 18 μg or oxitropium 0.2 mg × 3 mg), crossover study in 17 COPD patients. Treatment order was randomized across subjects. The subjects underwent a pulmonary function test and two modes of cardiopulmonary exercise (constant work rate and incremental exercise) testing using a cycle ergometer, with measurement of arterial catecholamines after each treatment period.
Results
Forced expiratory volume in 1 second and forced vital capacity were significantly larger in the tiotropium treatment group. In constant exercise testing, exercise endurance time was longer, with improvement in dyspnea during exercise and reduction in dynamic hyperinflation in the tiotropium treatment group. Similarly, in incremental exercise testing, exercise time, carbon dioxide production, and minute ventilation at peak exercise were significantly higher in the tiotropium treatment group. Plasma norepinephrine concentrations and dyspnea intensity were also lower during submaximal isotime exercise and throughout the incremental workload exercise in the tiotropium treatment group.
Conclusion
Tiotropium suppressed the increase of sympathetic activation during exercise at the end of the 6-week treatment, as compared with the effect of oxipropium. This effect might be attributed to improvement in lung function and exercise capacity and reduction in exertional dyspnea, which were associated with decreases in respiratory frequency and heart rate and reduced progression of arterial acidosis.
doi:10.2147/COPD.S28677
PMCID: PMC3355834  PMID: 22615527
chronic obstructive pulmonary disease (COPD); anticholinergics; exercise testing; sympathetic activation
20.  Post-prandial carbohydrate ingestion during 1-h of moderate-intensity, intermittent cycling does not improve mood, perceived exertion, or subsequent power output in recreationally-active exercisers 
Background
This study compared the effects of ingesting water (W), a flavored carbohydrate-electrolyte (CE) or a flavored non-caloric electrolyte (NCE) beverage on mood, ratings of perceived exertion (RPE), and sprint power during cycling in recreational exercisers.
Methods
Men (n = 23) and women (n = 13) consumed a 24–h standardized diet and reported 2–4 h post-prandial for all test sessions. After a familiarization session, participants completed 50 min of stationary cycling in a warm environment (wet bulb globe temperature = 25.0°C) at ~ 60-65% of heart rate reserve (146 ± 4 bpm) interspersed with 5 rest periods of 2 min each. During exercise, participants consumed W, CE, or NCE, served in a counterbalanced cross-over design. Beverage volume was served in 3 aliquots equaling each individual’s sweat losses (mean 847 ± 368 mL) during the familiarization session. Profiles of Mood States questionnaires (POMS) were administered and blood glucose levels were determined pre- and post- sub-maximal cycling. Following sub-maximal exercise, participants completed 3 30–s Wingate anaerobic tests (WAnT) with 2.5 min rest between tests to assess performance.
Results
Blood glucose was higher (p <  0.05) after 50 min of submaximal cycling just prior to the WAnT for CE (6.1 ± 1.7 mmol/L) compared to W (4.9 ± 1.5 mmol/L) and NCE (4.6 ± 1.2 mmol/L). Nonetheless, there were no differences among treatments in peak (642 ± 153, 635 ± 143, 650 ± 141 watts for W, NCE, and CE, respectively; p  =  0.44) or mean (455 ± 100, 458 ± 95, 454 ± 95 watts for W, NCE, and CE, respectively; p = 0.62) power for the first WAnT or mean (414 ± 92, 425 ± 85, 423 ± 82 watts, respectively; p = 0.13) power output averaged across all 3 WAnT. Likewise, RPE during submaximal exercise, session RPE, and fatigue and vigor assessed by POMS did not differ among beverage treatments (p > 0.05).
Conclusions
Carbohydrate ingestion consumed by recreational exercisers during a 1–h, moderate-intensity aerobic workout did not alter mood or perceived exertion, nor did it affect subsequent anaerobic performance under the conditions of this study. Drinking caloric sport beverages does not benefit recreational exercisers in a non-fasted state.
doi:10.1186/1550-2783-10-4
PMCID: PMC3562170  PMID: 23347391
Recreational exercise; Non-caloric; Sport beverage; RPE; POMS; Pre-exercise meal
21.  Assessing Causality in the Association between Child Adiposity and Physical Activity Levels: A Mendelian Randomization Analysis 
PLoS Medicine  2014;11(3):e1001618.
Here, Timpson and colleagues performed a Mendelian Randomization analysis to determine whether childhood adiposity causally influences levels of physical activity. The results suggest that increased adiposity causes a reduction in physical activity in children; however, this study does not exclude lower physical activity also leading to increasing adiposity.
Please see later in the article for the Editors' Summary
Background
Cross-sectional studies have shown that objectively measured physical activity is associated with childhood adiposity, and a strong inverse dose–response association with body mass index (BMI) has been found. However, few studies have explored the extent to which this association reflects reverse causation. We aimed to determine whether childhood adiposity causally influences levels of physical activity using genetic variants reliably associated with adiposity to estimate causal effects.
Methods and Findings
The Avon Longitudinal Study of Parents and Children collected data on objectively assessed activity levels of 4,296 children at age 11 y with recorded BMI and genotypic data. We used 32 established genetic correlates of BMI combined in a weighted allelic score as an instrumental variable for adiposity to estimate the causal effect of adiposity on activity.
In observational analysis, a 3.3 kg/m2 (one standard deviation) higher BMI was associated with 22.3 (95% CI, 17.0, 27.6) movement counts/min less total physical activity (p = 1.6×10−16), 2.6 (2.1, 3.1) min/d less moderate-to-vigorous-intensity activity (p = 3.7×10−29), and 3.5 (1.5, 5.5) min/d more sedentary time (p = 5.0×10−4). In Mendelian randomization analyses, the same difference in BMI was associated with 32.4 (0.9, 63.9) movement counts/min less total physical activity (p = 0.04) (∼5.3% of the mean counts/minute), 2.8 (0.1, 5.5) min/d less moderate-to-vigorous-intensity activity (p = 0.04), and 13.2 (1.3, 25.2) min/d more sedentary time (p = 0.03). There was no strong evidence for a difference between variable estimates from observational estimates. Similar results were obtained using fat mass index. Low power and poor instrumentation of activity limited causal analysis of the influence of physical activity on BMI.
Conclusions
Our results suggest that increased adiposity causes a reduction in physical activity in children and support research into the targeting of BMI in efforts to increase childhood activity levels. Importantly, this does not exclude lower physical activity also leading to increased adiposity, i.e., bidirectional causation.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
The World Health Organization estimates that globally at least 42 million children under the age of five are obese. The World Health Organization recommends that all children undertake at least one hour of physical activity daily, on the basis that increased physical activity will reduce or prevent excessive weight gain in children and adolescents. In practice, while numerous studies have shown that body mass index (BMI) shows a strong inverse correlation with physical activity (i.e., active children are thinner than sedentary ones), exercise programs specifically targeted at obese children have had only very limited success in reducing weight. The reasons for this are not clear, although environmental factors such as watching television and lack of exercise facilities are traditionally blamed.
Why Was This Study Done?
One of the reasons why obese children do not lose weight through exercise might be that being fat in itself leads to a decrease in physical activity. This is termed reverse causation, i.e., obesity causes sedentary behavior, rather than the other way around. The potential influence of environmental factors (e.g., lack of opportunity to exercise) makes it difficult to prove this argument. Recent research has demonstrated that specific genotypes are related to obesity in children. Specific variations within the DNA of individual genes (single nucleotide polymorphisms, or SNPs) are more common in obese individuals and predispose to greater adiposity across the weight distribution. While adiposity itself can be influenced by many environmental factors that complicate the interpretation of observed associations, at the population level, genetic variation is not related to the same factors, and over the life course cannot be changed. Investigations that exploit these properties of genetic associations to inform the interpretation of observed associations are termed Mendelian randomization studies. This research technique is used to reduce the influence of confounding environmental factors on an observed clinical condition. The authors of this study use Mendelian randomization to determine whether a genetic tendency towards high BMI and fat mass is correlated with reduced levels of physical activity in a large cohort of children.
What Did the Researchers Do and Find?
The researchers looked at a cohort of children from a large long-term health research project (the Avon Longitudinal Study of Parents and Children). BMI and total body fat were recorded. Total daily activity was measured via a small movement-counting device. In addition, the participants underwent genotyping to detect the presence of several SNPs known to be linked to obesity. For each child a total BMI allelic score was determined based on the number of obesity-related genetic variants carried by that individual. The association between obesity and reduced physical activity was then studied in two ways. Direct correlation between actual BMI and physical activity was measured (observational data). Separately, the link between BMI allelic score and physical activity was also determined (Mendelian randomization or instrumental variable analysis). The observational data showed that boys were more active than girls and had lower BMI. Across both sexes, a higher-than-average BMI was associated with lower daily activity. In genetic analyses, allelic score had a positive correlation with BMI, with one particular SNP being most strongly linked to high BMI and total fat mass. A high allelic score for BMI was also correlated with lower levels of daily physical activity. The authors conclude that children who are obese and have an inherent predisposition to high BMI also have a propensity to reduced levels of physical activity, which may compound their weight gain.
What Do These Findings Mean?
This study provides evidence that being fat is in itself a risk factor for low activity levels, separately from external environmental influences. This may be an example of “reverse causation,” i.e., high BMI causes a reduction in physical activity. Alternatively, there may be a bidirectional causality, so that those with a genetic predisposition to high fat mass exercise less, leading to higher BMI, and so on, in a vicious circle. A significant limitation of the study is that validated allelic scores for physical activity are not available. Thus, it is not possible to determine whether individuals with a high allelic score for BMI also have a propensity to exercise less, or whether it is simply the circumstance of being overweight that discourages activity. This study does suggest that trying to persuade obese children to lose weight by exercising more is likely to be ineffective unless additional strategies to reduce BMI, such as strict diet control, are also implemented.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001618.
The US Centers for Disease Control and Prevention provides obesity-related statistics, details of prevention programs, and an overview on public health strategy in the United States
A more worldwide view is given by the World Health Organization
The UK National Health Service website gives information on physical activity guidelines for different age groups
The International Obesity Task Force is a network of organizations that seeks to alert the world to the growing health crisis threatened by soaring levels of obesity
MedlinePlus—which brings together authoritative information from the US National Library of Medicine, National Institutes of Health, and other government agencies and health-related organizations—has a page on obesity
Additional information on the Avon Longitudinal Study of Parents and Children is available
The British Medical Journal has an article that describes Mendelian randomization
doi:10.1371/journal.pmed.1001618
PMCID: PMC3958348  PMID: 24642734
22.  Effects of 12 Weeks of Combined Exercise Training on Visfatin and Metabolic Syndrome Factors in Obese Middle-Aged Women 
Visfatin is a highly expressed protein with insulin-like functions located predominantly in visceral adipose tissue and has been linked to obesity and increased health risks. The purpose of this study was to examine the effects of 12 weeks of combined exercise training on visfatin and metabolic syndrome factors in obese middle-aged women. Subjects were randomly assigned to either a training (n = 10) or control (n = 10) group. The training group exercised for 1 hour, 3 days per week during the 12 week supervised training program. The training program included 3 sets of 10 repetition maximum (10RM) resistance exercise as well as aerobic exercise at an intensity of 60-70% of their heart rate reserve (HRR). The control group was asked to maintain their normal daily activities. Two-way (group X time) repeated measured analysis of variance revealed no significant main effects, but there was a significant group X time interaction for the following variables: body weight (p < 0.01), percent body fat (% fat) (p < 0.01), waist hip ratio (WHR) (p < 0.01), diastolic blood pressure (DBP) (p < 0.05), fasting glucose level (p < 0.01), triglyceride levels (TG) (p < 0.01), high density lipoprotein cholesterol levels (HDL-C) (p < 0.05), and visfatin (p < 0.01). In conclusion, the 12 week combined resistance and aerobic training program used in this study was very effective for producing significant benefits to body composition and metabolic syndrome factors, as well as lowering visfatin levels in these obese middle-aged women.
Key pointsRecent studies have linked visfatin to obesity and increased health risks.The study was done to investigate the effects of 12 weeks of combined exercise training on visfatin and metabolic syndrome factors in obese middle-aged women.The exercise program used in this study was found to be very effective for lowering visfatin levels in obese middle-aged women.
PMCID: PMC3737906  PMID: 24149317
Metabolic syndrome; combined resistance; aerobic exercise; visfatin
23.  Increased plasma levels of soluble vascular endothelial growth factor (VEGF) receptor 1 (sFlt-1) in women by moderate exercise and increased plasma levels of VEGF in overweight/obese women 
The incidence of breast cancer is increasing worldwide, and this seems to be related to an increase in lifestyle risk factors, including physical inactivity, and overweight/obesity. We previously reported that exercise induced a circulating angiostatic phenotype characterized by increased sFlt-1 and endostatin and decreased unbound-VEGF in men. However, there is no data on women. The present study determines the following: 1) whether moderate exercise increased sFlt-1 and endostatin and decreased unbound-VEGF in the circulation of adult female volunteers; 2) whether overweight/obese women have a higher plasma level of unbound-VEGF than lean women. 72 African American and Caucasian adult women volunteers aged from 18–44 were enrolled into the exercise study. All the participants walked on a treadmill for 30 minutes at a moderate intensity (55–59% heart rate reserve), and oxygen consumption (VO2) was quantified by utilizing a metabolic cart. We had the blood samples before and immediately after exercise from 63 participants. ELISA assays (R&D Systems) showed that plasma levels of sFlt-1 were 67.8±3.7 pg/ml immediately after exercise (30 minutes), significantly higher than basal levels, 54.5±3.3 pg/ml, before exercise (P < 0.01; n=63). There was no significant difference in the % increase of sFlt-1 levels after exercise between African American and Caucasian (P=0.533) or between lean and overweight/obese women (P=0.892). There was no significant difference in plasma levels of unbound VEGF (35.28±5.47 vs. 35.23±4.96 pg/ml; P=0.99) or endostatin (111.12±5.48 vs. 115.45±7.15 ng/ml; P=0.63) before and after exercise. Basal plasma levels of unbound-VEGF in overweight/obese women were 52.26±9.6 pg/ml, significantly higher than basal levels of unbound-VEGF in lean women, 27.34±4.99 pg/ml (P < 0.05). The results support our hypothesis that exercise-induced plasma levels of sFlt-1 could be an important clinical biomarker to explore the mechanisms of exercise training in reducing breast cancer progression and that VEGF is an important biomarker in obesity and obesity-related cancer progression.
doi:10.1097/CEJ.0b013e328353ed81
PMCID: PMC3449013  PMID: 22609636
Exercise; Young adult women; Overweight/obese; sFlt-1; Endostatin; VEGF
24.  Relationship between skeletal muscle insulin resistance, insulin-mediated glucose disposal, and insulin binding. Effects of obesity and body fat topography. 
Journal of Clinical Investigation  1984;74(4):1515-1525.
Skeletal muscle sensitivity and responsiveness to insulin and their relationship to overall glucose disposal and insulin binding were determined in 89 premenopausal women of varying body fat topography (waist/hips girth ratio [WHR] 0.64-1.02) and obesity level (percentage of ideal body weight 92-230). As a marker of insulin action, the percentage of total glycogen synthase present in the I form (glucose-6-phosphate independent) was measured in quadriceps muscle biopsies. The increase in percentage of synthase I 1 h after oral glucose loading was not significantly different between nonobese and obese weight-matched subgroups of increasing WHR, but this response was maintained at the expense of increasing plasma insulin levels as the WHR rose. The increase in percentage of synthase I in response to submaximal steady state plasma insulin (SSPI) of approximately 100 microU/ml achieved by the infusion of somatostatin, insulin, and glucose, however, was significantly lower in obese than in nonobese subjects, and was inversely correlated with WHR. The increase in percentage of synthase I correlated inversely with the steady state plasma glucose (SSPG) concentration, which is an index of the efficiency of overall glucose disposal, and directly with insulin binding to circulating monocytes. Insulin binding also correlated inversely with WHR and with fasting plasma insulin levels. When obese subjects were separated into three weight-matched subgroups on the basis of increasing WHR, significant trends to decreased percentage of synthase I response, increased SSPG, and decreased insulin binding were found. In women with predominantly upper body obesity (WHR greater than 0.85), the increase in percentage of synthase in response to submaximal SSPI was diminished, but there was no impairment of percentage of synthase I responsiveness to supramaximal SSPI of approximately 1,000 microU/ml. At supramaximal SSPI levels, SSPG in four obese women was normal, whereas in five women, SSPG concentrations were markedly increased. Our results suggest that in premenopausal women, impaired skeletal muscle insulin sensitivity that results in decreased glucose storage capacity may contribute to the diminished efficiency of glucose disposal and insulin resistance that are associated with upper body obesity. The impairment in skeletal muscle sensitivity may be overcome in vivo at the expense of increasing plasma insulin levels, with maximal responsiveness remaining unimpaired. This defect may result from a reduction in insulin receptor number which could, in turn, be secondary to persistently elevated fasting plasma insulin levels. In some upper body segment obese women, however, an additional defect affecting other insulin-sensitive pathways may also be present.
Images
PMCID: PMC425322  PMID: 6148358
25.  The Effects of Regular Aerobic Exercise on Renal Functions in Streptozotocin Induced Diabetic Rats 
Diabetic nephropathy is a feared complication of diabetes since it can lead to end-stage renal failure and also it is a risk factor of cardiovascular disease. The important clinical problems caused by diabetic nephropathy are proteinuria and decreased renal function. Exercise is a cornerstone of diabetes management, along with diet and medication. Since acute exercise causes proteinuria and decreases glomerular filtration rate, the effect of exercise on diabetic nephropathy is controversial. The aim of this study was to investigate the effect of regular aerobic exercise on microalbuminuria and glomerular filtration rate in diabetic rats. Moderate diabetes was induced by streptozotocin (45 mg/kg IV) in rats and an aerobic exercise- training program on a treadmill was carried out for 8 weeks. Four groups of rats; control sedentary (CS), control exercise (CE), diabetic sedentary (DS) and diabetic exercise (DE) were included in the study. Blood glucose levels were determined from the plasma samples taken at the end of 4 weeks of stabilization period and 8 weeks of training program. Creatinine clearance (CCr) and microalbuminuria (MA) levels were determined to evaluate renal functions. The analyzed data revealed that regular aerobic exercise: 1) significantly decreased the plasma glucose level of the DE group compared to the DS group (p < 0.05), 2) significantly decreased the microalbuminuria level of the DE group compared to those of DS group (p < 0.01), 3) significantly decreased the creatinine clearance levels of the DE and CE groups compared to those of CS group (p < 0.05). The results of this study suggest that despite of decreasing creatinine clearance, regular submaximal aerobic exercise has a preventive effect on development of microalbuminuria and thus may retard nephropathy in diabetic rats.
Key pointsRegular submaximal aerobic exercise can facilitate the control of blood glucose level in diabetic rats.Streptozotocin induced diabetes may cause microalbuminuria and regular submaximal aerobic exercise may have a preventive effect on renal functions.
PMCID: PMC3761734  PMID: 24149699
Aerobic exercise; microalbuminuria; nephropathy; diabetes mellitus

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