The present study is the largest to date to examine level of physical activity among an unselected group of adolescents and young adults (ages 11 through 24 years) with TIDM studied when they presented for their routine diabetes clinic appointment. The results of this study indicate that adolescent females with T1DM are typically engaged in at least 60 minutes of moderate to vigorous physical activity about 3 days per week, which is similar to results found in other studies [24
]. The reported frequency of physical activity in the present study falls short of meeting the guidelines of the AAP [23
], the ADA [22
], and the CDC [21
], which recommend that children engage in at least 60 minutes of physical activity per day.
As expected, we found a correlation between the number of physically active days and A1c, in agreement with findings in some previous studies [13
]. This is of important clinical significance since the DCCT [3
] and other studies [25
] have demonstrated conclusively that improved glycemic control, as assessed by A1c, markedly reduces the development of and progression of microvascular complications of diabetes such as retinopathy, neuropathy, and nephropathy. However, it should also be noted that other studies have not found an association between physical activity and HbA1c [14
We also found that Hispanic females with TIDM were overall less physically active than NHW adolescents with TIDM. These results are similar to other studies that have found that regardless of TIDM status, Hispanic girls tend to be less physically active than their NHW counterparts [26
]. This might partly be attributable to lower socioeconomic status among Hispanic females which has been found to be associated with increased risk for a sedentary lifestyle [24
More frequent weekly physical activity was reported among girls 11–15 years of age with significantly less frequent physical activity reported by girls between 16–19 years of age. Our results are similar to other studies that have also found physical activity to decline and sedentary behavior to become more common during adolescence [27
]. Pate et al. specifically examined change in participation in activities during adolescence in girls and found that vigorous physical activity declined from 45.4% in 8th grade to 34.1% in 12th grade. Interestingly, the probability of participating in several forms of vigorous physical activity in 12th grade was strongly associated with participation in those activities in 8th grade [28
]. Thus, encouragement of physical activity in those with T1DM at a young age might be important in helping to establish maintenance of physical activity during adolescence and beyond.
Why are not adolescent females with TIDM more physically active? One study has found that the fear of hypoglycemia was the strongest barrier to regular physical activity [29
]. This fear could partly be due to the mismanagement of diabetes during times of exercise. In fact, one study that looked at adolescents with TIDM found that only fifty percent of the patients reported monitoring blood glucose levels during exercise, and only 32% changed insulin dose according to blood glucose levels. Also, hypoglycemic episodes (37.7%) were more frequently reported than hyperglycemic episodes [30
]. Thus, the complexities of diabetes surveillance and fear of hypoglycemia during exercise can become a unique challenge to those with TIDM.
It is also important that health care providers are familiar with ADA guidelines of physical activity. The ADA recommends that blood glucose monitoring should be done before and at the termination of exercise and at hourly intervals during episodes of prolonged strenuous activity. Fifteen grams of carbohydrates may be administered as a readily absorbed sugar if blood glucose levels are <100
mg/dL during the period of exercise [22
]. The DirecNet study group has also found that discontinuing basal insulin during exercise is an effective strategy in those using insulin pumps for reducing hypoglycemia [31
]. In addition, they have also found that overnight hypoglycemia after exercise is common in children with TIDM and recommend modifying diabetes management following afternoon exercise to reduce the risk of hypoglycemia [32
]. Thus, adolescents with TIDM should be involved in comprehensive teaching programs for self-management of diabetes [33
] and should be aware that the existing guidelines are useful, but the exact adjustments of insulin dose must be made on an individual basis [34
] with the help of their health care provider.
There were some limitations to our study. First, the participants were predominantly of NHW and Hispanic race/ethnicity, and so we were not able to provide reliable estimates of level of physical activity in other racial/ethnic groups. Also, we did not have a nondiabetic control group to compare physical activity. In addition, there is also the potential for recall bias with the use of self-reported questionnaires. Also, level of energy expenditure is multifactorial and often cannot be well captured by use of a questionnaire [35
]. However, similar physical activity questionnaires to the one used in this study have also been found to be valid, reliable, and suitable to use for the purpose of data collection in child and adolescent populations [36
]. Further, more frequent reported physical activity was significantly associated with a lower resting pulse and diastolic blood pressure, suggesting that expected physiologic changes were present in association with reported levels of activity.
In conclusion, adolescent females with TIDM report exercising at least 60 minutes a day on 3 days out of a typical week. Only 5% of our subjects met the international recommendations of 60 minutes of moderate-to-vigorous activity per day. Health care providers need to continually encourage adolescent females with T1DM to exercise, and barriers to physical activity need to be reduced, with special attention to Hispanic adolescents and those between 16–19 years of age. Thus, increased physical activity is associated with improved glycemic control in adolescents with TIDM which can ultimately lead to decreased micro- and macrovascular complications of diabetes.