A Single Session of Handcycle Exercise Can Increase Glucose Tolerance in Adolescents

Abstract

We previously showed that moderate-intensity exercise before a meal resulted in increased insulin sensitivity in habitually sedentary children. That study used mostly walking and cycling; it is unclear whether those results are translatable to youth with spinal cord disorders who rely on upper body muscles for mobility. PURPOSE: To measure the impact of a single session of upper body exercise on oral glucose tolerance and insulin sensitivity METHODS: Participants were recreationally active adolescents with either spina bifida or cerebral palsy (SB/CP, 3F/4M, 15±1 y), or healthy controls (4F/7M, 15±1 y). The SB/CP group had higher body fat (SB/CP: 38±4, Control: 25±3 %, p<0.03) but cardiorespiratory fitness (VO2peak) during handcycle exercise was similar between groups (SB/CP: 18.9±2.3, Control: 20.4±2.2 ml/kg/min). A 75-gram oral glucose tolerance test was performed on two separate days. A Rest trial was completed after refraining from vigorous activity for 2 days. An Exercise trial included a 36-min bout of handcycle exercise (70% HRmax with 5 x 30-second high-intensity bursts near the end) completed 32 minutes before consuming the glucose. RESULTS: Fasting glucose (SB/CP: 87±3, Control: 89±2 mg/dl) and insulin (SB/CP: 7.3±1.8, Control: 7.4±1.9 μIU/ml) were normal in both groups. Glucose area under the curve (SB/CP: 15.3±1.2, Control: 16.1±0.9 mg-min/dl/1000) did not differ between groups on the Rest trial and declined 13% in SB/CP (6 of 7 participants, p=0.109) and 9% in Control (8 of 11 participants, p=0.045), respectively, on the Exercise trial. Insulin area under the curve (SB/CP: 10.4±2.3, Control: 9.8±1.4 μIU-min/ml/1000) did not differ between groups on the Rest trial and was not significantly altered by exercise. Fasting free-fatty acid concentration was also similar between groups (0.64±0.06 mM), equally suppressed by insulin following glucose ingestion (75±5%), and not altered by exercise. Oral glucose insulin sensitivity index was increased 16% (p=0.028) by exercise in the Control group but was not significantly changed in the SB/CP group. CONCLUSIONS: These data demonstrate that a short bout of upper body exercise improves glucose tolerance, likely through insulin-independent pathways, in adolescents with and without spinal cord disorders and could therefore reduce risk for diabetes.