The effect of 6-month supervised exercise on cardiovascular risk factors was studied in a group of 196 adolescentts with type 1 diabetes mellitus. Despite the well-known benefit of physical activity in improving known risk factors for atherosclerosis, unfortunately this modality was ignored by parents and patients who fear the consequence of hypoglycemia, which can occur during, immediately after, or many hours after physical activity, making it one of limiting factors for its practice in children and adolescents with type 1 DM.
The frequency of hypoglycemia experienced by the intervention group was the same in comparison to the control group. Our results might be influenced by the fact that the exercise in this study is a planned one and patients do not exert any unscheduled activity. This will give the chance for an educated patient the ability to learn about his individual glucose response to exercise and eventually establish an individual strategy to prevent exercise-induced hypoglycemia. Framework to guide management of achieving blood glucose goals without excessive hypoglycemia during and after exercise can be accomplished through individualized meal planning, flexible insulin regimens and algorithms, self monitoring blood glucose and education promoting decision-making based on documentation and review of previous results.
Some studies [10
] found that the frequency of exercise had no significant influence on the frequency of severe hypoglycemia or hypoglycemia with occurrence of seizure or loss of consciousness.
In their study in 2006, DirecNet group
] found that in youth with T1DM, prolonged moderate aerobic exercise results in a consistent reduction in plasma glucose and the frequent occurrence of hypoglycemia when pre-exercise glucose concentrations are <120 mg/dl. Moreover, treatment with 15 g of oral glucose is often insufficient to reliably treat hypoglycemia during exercise in these youngsters.
Of particular significance is the result of reduction in insulin requirements after performing exercise. The authors speculated that patients tend to reduce their insulin dosage to prevent exercise induced hypoglycemia. Moreover, exercise acutely lowers the blood glucose concentration to an extent that depends on its intensity, duration and the concurrent level of insulinaemia [14
]. It also increases insulin-stimulated glucose uptake in muscle, putting in mind that this effect is higher in trained muscle than in untrained muscle, leading to a reduction in the insulin requirement [15
Our results are in agreement with that of Herbest et al.
] who confirmed that RPA is associated with a lower insulin dosage as a long-term effect. Many other studies [16
] found the same significant effect of regular physical exercise on the daily insulin dose.
Our study shows that HbA1c level is influenced by frequency of exercise, as it was lower in group C with more frequent exercise, this may be because physical activity is known to acutely reduce the blood glucose level and to increase insulin sensitivity [19
]. However, Allen et al
] have shown that the better control of glycemia (lower HbA1c
level) due to regular exercise is related to more frequent mild and severe hypoglycemia and hence decreasing HbA1c levels. The reduction in HbA1c level over time is clinically significant, as the Diabetes Control and Complications Trial (DCCT) reported a 21% to 49% decreased risk for microvascular complications with every 1% decrease in HbA1c [21
The relationship between physical fitness and HbA1c levels has been previously studied; however, the results were controversial. Herbst et al
] studied the cardiovascular risk factors among 23, 251 patients (3-18 years) with type 1 diabetes, found that mean HbA1c was 7.9%. The frequency of RPA defined as physical activity performed regularly at least once a week for at least 30 minutes continuously for at least 1 year, excluding school sports ranged between 0 and 9 times/week (average 1.29 times/week). Of the patients, 44.7% were not physically active, 37.0% performed RPA 1-2 times/week, and 18.3% performed RPA 3 times/week. HbA1c was lower in patients with a higher frequency of RPA (P
< 0.00001), Higher levels of HbA1c were associated with higher levels of cholesterol, LDL cholesterol, and triglycerides (P
< 0.0001 each) and a lower level of HDL cholesterol (P
In addition, Herbst et al
] who studied the relationship between the frequency of RPA and glycemic control in patients with T1DM aged 3 to 20 years revealed that HbA1c level was higher in the groups with less frequent RPA (8.4% in group RPA0 vs 8.1% in group RPA2; P
< .001). This effect was found in both sexes and in all age groups (P
< .001). Multiple regression analysis revealed that RPA was one of the most important factors influencing the glycosylated hemoglobin level. Other studies [23
] also revealed that the more frequent exercise performed the lower HbA1c level.
] aimed to assess the effect of 6-month exercise program in obese children and showed that HbA1c level was decreased after the exercise program but not a statistically significant decrease, this may be due to the limited time of the program, or due to compliance of patients.
It is worth noting the study of Harmer et al
] which aimed to investigate the effects of high intensity exercise (HIE) training on glycemia and acid-base regulation in type 1 diabetes, found that exercise training did not alter HbA1c in type 1 diabetic subjects (pre-exercise 8.6 ± 0.8%, post-exercise 8.1 ± 0.6%; P
= 0.09). Furthermore, Ramalho et al
] evaluated the effect of aerobic versus resistance training on metabolic control in type-1 diabetes patients and found that neither resistance nor aerobic training had improved glycated hemoglobin in type-1 diabetes patients. Some studies have failed to show the effect of exercise on HbA1c [27
]. The controversial results might be because of the different methodological approaches or because of different number of studied groups.
In the current study, patients in the exercise group have gained more benefits from joining the exercise program. This group showed significant improvements related to lipid profile and found that frequent exercise was associated with statistically significant decrease in the lipid profile levels of LDL-c, TG, & cholesterol, and statistically significant increase in HDL-c. Exercise is considered as one approach for maintaining optimal lipid levels in addition it is a low-cost, non- pharmacologic intervention that is available to the vast majority of children and adolescents.
Our findings were consistent with the previous report by Herbst et al
] who found that increasing frequency of RPA was associated with lower total cholesterol, LDL cholesterol, and triglycerides and higher HDL cholesterol. Moreover, George et al
], Lehmann et al
], Meyer et al
], Valerio et al
] proved the effect of exercise on plasma lipids and found that the frequency of exercise was associated with a significant decrease in the levels of LDL-c, cholesterol & TG, and increase in HDL-c level.
Where as Gordan et al
] whom studied the effect of exercise therapy on lipid profile and oxidative stress indicators in patients with type 1 diabetes, found that 6-month exercise program significantly decreased total cholesterol (P value < 0.001) but didn't affect TG, LDL-c or HDL-c.
In their study in 2009, Leite et al
] analyzed the effects of physical exercise and nutritional guidance on body composition, physical fitness, lipid profile and insulin resistance among obese adolescents and found after 12 weeks exercise program 3 times per week that TG decreased significantly (P < 0.001) and HDL increased significantly (P < 0.001) but total cholesterol & LDL had shown no significant decrease. In addition Rigla et al
] who evaluated the effect of physical exercise (3-month exercise program) on blood pressure, the lipid profile, lipoprotein(a) and LDL-c in type 1 & 2 diabetic patients, presented an increase of HDL-c in type 1 patients (P
< 0.05), while a decrease of LDL-C in type 2 patients (P
On the contrary, other studies [18
] have failed to show the effect of exercise on lipid profile, this may be due to the limited time of the program, or due to compliance of patients. Also total cholesterol, LDL-cholesterol, TG and plasminogen activator inhibitor-1 (PAI-1) levels were lower in highly trained athletes group in relation to sedentary subjects (p < 0.01). These results indicate that lifestyle associated with high intensity and high volume exercise induces favorable changes in the lipid profile and PAI-1 levels, and this may reduce the risk of cardiovascular diseases [36
Although weight and BMI of participants in this study before joining exercise program were normalized, yet they were towards the high normal side. This is important because, during puberty, adolescents have a higher risk for gaining weight. Moreover, there is an epidemic towards increase prevalence of overweight and obesity among children and adolescents. Exercise might keep the BMI or body weight low due to its lipolytic effect. At the end of the study; the average body weight was statistically different between the two intervention groups and the control group keeping the patients who performed exercise within 50th
percentiles and not causing severe weight loss that may have affected the growth and development of those patients in their growing ages. Accumulating evidence [37
] suggests that physical activity may enhance weight loss and, in particular, weight maintenance thereafter to achieve and maintain ideal body weight and body composition when used along with an appropriate calorie controlled meal plan and an increase in calcium and vitamin D supplementation [38
Leite et al
] and Kelley et al
] proved that aerobic exercise improved percent of body fat, aerobic capacity & decreased body weight, BMI, WC significantly.
Whereas, other studies [17
] found no significant change in BMI after exercise, but found a significant change in waist circumference after the exercise program.
Little difference was obseved concerning blood pressure either systolic or diastolic in the three groups after exercise program, this may be due to the young age of the patients as most of them were normotensive.
] found that the regular physical exercise did not affect the systolic blood pressure, but it decreased the diastolic blood pressure significantly (P value < 0.001).
In contrast, other studies [16
] found that the systolic blood pressure was affected significantly (P value = 0.048) but the diastolic blood pressure was not affected by the exercise program.
Many studies used different aspects of exercise regimen. Lehman et al. [31
] included well-controlled subjects with IDDM (n = 20; HbA1c = 7.6%) and they were engaged in a regular exercise program over a period of 3 months involving endurance sports such as biking, long-distance running, or hiking. Ramalho et al. [17
] evaluated the effect of aerobic versus resistance training on metabolic control in type-1 diabetes patients. Thirteen non-active patients, ranging in age from 13-30 yrs, were submitted to a 12-week aerobic exercise (Group A, n = 7) or resistance training (Group B, n = 6) period. Durak et al. [23
] studied on eight male type 1 diabetic subjects (mean +/- SD age 31 +/- 3.5 yr) and their program consisted of heavy-resistance weight training 3 days/wk for 10 wk, concentrating on the strengthening of major muscle groups through progressive resistance. Guffee et al. [11
] evaluated eight volunteers with type 1 diabetes (aged 18.6 ± 2.1 years) that joined either the control rest protocol (CON) or intermittent high-intensity exercise protocol (IHE). In patients with type 2 diabetes, a few studies have looked at the combined effect of aerobic and resistance exercises [39
]. However, our training program aimed to combine the different elements of an exercise regimen (aerobic, anaerobic, strengthening, neuromuscular and balance) and to address various aspects in type1 diabetes patient to help improve their physical function and quality of life. We aimed to improve blood glucose control and insulin sensitivity, reduce body fat, reduce stress, increase cardiovascular benefits aswell as increase muscle strength and endurance. Flexibility exercises and stretching was used to help prevent injury and maintain and or increase range of motion of joints. The neuromuscular and balance training part of our program with special emphasis on the lower limbs was unique and aimed to improve the coordination, balance and physical function of patients.
In conclusion our results implicated that exercise might greatly benefit many patients with diabetes by improving their metabolic profile, dyslipidemia, aiding in their weight loss and maintaining their blood pressure; these effects may translate into an improved vascular disease risk profile in adolescents with diabetes. The challenge is to develop strategies that allow individuals with T1DM to participate in activities that are consistent with their lifestyle and culture in a safe and enjoyable manner, and discouraging sedentary activities, especially time spent in front of the TV or computer monitor. Exercise should be an important component of self -care activity in the management of patients with T1DM.