Exercise at lunchtime: effect on glycemic control and oxidative stress in middle-aged men with type 2 diabetes.

PURPOSE: Postprandial hyperglycemia and glycemic oscillations have been associated with increased oxidative stress. We sought to investigate the effect of two walking exercise protocols performed during lunchtime on glycemic control and oxidative stress in type 2 diabetic (T2D) patients. METHODS: Nine T2D patients participated in three randomized crossover trials; a control trial (Con), with participants having a standard lunch followed by their normal daily activities and two exercise trials (ContEx and Splitex). In ContEx, subjects performed 40 min of brisk walking 40 min after lunch, whereas in SplitEx the walking exercise was divided in two 20-min isoenergetic bouts, before and 40 min after meal. 24-h glycemic control was monitored by continuous glucose monitoring. 24-h urinary levels of 8-iso PGF2ɑ were measured as a marker of oxidative stress. RESULTS: SplitEx resulted in less time spent in moderate hyperglycemia after lunch vs ContEx (42.4 ± 38.7% vs 68.2 ± 32.7%, P = 0.04). ContEx reduced hyperglycemic time after breakfast consumed the morning after the exercise session (58.3 ± 29.6 Con vs 40.2 ± 33.4% ContEx, P = 0.02). Compared with Con, 24-h urinary isoprostanes were decreased both in ContEx (-68%, P = 0.02) and SplitEx (-63%, P = 0.04). CONCLUSIONS: Splitting an exercise session into two bouts, pre- and post-lunch, affects mainly the glycemic response to lunch, while a single-continuous isoenergetic session exerts its effect later in the 24-h period. Both exercise modalities effectively attenuate systemic oxidative stress with similar overall benefits.

Neuromuscular dysfunction in diabetes: role of nerve impairment and training status.

PURPOSE: The purpose of this study was to investigate the effect of diabetes, motor nerve impairment, and training status on neuromuscular function by concurrent assessment of the torque-velocity relationship and muscle fiber conduction velocity (MFCV). METHODS: Four groups were studied (n = 12 each): sedentary patients with diabetes in the first (lower) and fourth (higher) quartile of motor nerve conduction velocity (D1 and D4, respectively), trained diabetic (TD) patients, and nondiabetic sedentary control (C) subjects. Maximal isometric and isokinetic contractions were assessed over a wide range of angular velocities for the elbow flexors and knee extensors to evaluate the torque-velocity relationship. Simultaneously, MFCV was estimated from surface electromyography of the vastus lateralis and biceps brachii. RESULTS: Isometric strength was similar among groups. The dynamic strength of elbow flexors was reduced in patients with diabetes at the higher contraction speeds. The strength of knee extensors was lower in sedentary patients with diabetes at all velocities considered, with significantly lower values in D1 than that in D4 at 60°, 90°, and 120°·s(-1), whereas it was similar between TD and C subjects, especially at low contraction velocities. At the vastus lateralis, but not the biceps brachii, MFCV was lower in D1 and D4 as compared with TD and C subjects, showing similar values. CONCLUSIONS: Muscle weakness in diabetes affects also the upper limb, although to a lower extent than the lower limb, is only partly related to motor nerve impairment, and is dependent on contraction velocity. Exercise training might counteract diabetes-induced alterations in muscle fiber contractile properties and MFCV.

Different effect of cadence on cycling efficiency between young and older cyclists.

PURPOSE: We investigated the difference in the cadence-efficiency relationship between young and older competitive cyclists. METHODS: Eight young (24.3 ± 5.3 yr) and eight older (65.6 ± 2.8 yr) competitive cyclists participated in two laboratory sessions. The first consisted of an incremental maximal cycling test to determine the freely chosen pedal cadence and the maximal power output at VO2max and the second for the determination of gross efficiency (GE), calculated as the ratio of external work and energy expenditure (VO2). The latter test consisted of 6-min cycling exercise bouts at 40% and 60% of maximal power output and at a cadence of 40, 60, 80, 100, and 120 rpm. RESULTS: GE was lower in older cyclists than that in young cyclists at all cadences considered and at both levels of power output (P < 0.01). Peak efficiency was reached at 60 rpm in young cyclists (21.2% ± 1.9%), whereas in older cyclists this was observed already at 40 rpm and was not different from that at 60 rpm (18.3% ± 0.6%). The decline in GE with the increase in cadence was more pronounced in older than in young cyclists (P < 0.01) and was mitigated by the increase in power output more in the latter than in the former. These observations were in line with a lower freely chosen cadence recorded during the maximal test in older than that in young (P < 0.01). CONCLUSIONS: The present data indicate that the effect of cadence on cycling efficiency is different between young and older cyclists and that it seems more disadvantageous for the latter to use high cadences. This may help explain why our older cyclists chose to pedal at lower cadences than the younger.