Effect of adiposity on insulin action after acute and chronic resistance exercise in non-diabetic women.

PURPOSE: Obesity may attenuate metabolic health improvements following lifestyle interventions. However, the effect of adiposity on insulin action following resistance exercise in young non-diabetic women is unknown. The purpose of this study was to test the hypothesis that adiposity attenuates improvements in insulin sensitivity and glucose-stimulated insulin secretion (INS0-60/GLC0-60) after both acute resistance exercise (ARE) and progressive training (PRT). METHODS: Twenty-six young non-diabetic women (21.2 ± 0.7 years) were randomly assigned to control (C; n = 7; BF 40.1 ± 2.1 %) or exercise groups: normal body fat (NBF; n = 8; BF 29.9 ± 2.3 %) and high body fat (HBF; n = 12; BF 48.2 ± 1.4 %). Acute whole-body exercises were performed at 60 % of 1-RM for three sets of 8-12 repetitions, and PRT was performed 3 days/week for 7 weeks. A 75 g OGTT was conducted before and after ARE and PRT to estimate insulin sensitivity (Matsuda index) and INS0-60/GLC0-60. Insulin area under the curve (AUC) was calculated using the trapezoidal model. RESULTS: ARE had no statistical effect on insulin action across groups. Strength and fat-free mass (via DXA) increased after PRT in both NBF and HBF (p < 0.05), but only HBF women decreased BF (p < 0.01). HBF women were less insulin sensitive at baseline compared to NBF women (p < 0.05). Insulin sensitivity increased 95 % and INS0-60/GLC0-60 decreased 32 % following PRT in NBF, but not HBF or C (p < 0.05). After training, enhanced insulin sensitivity was inversely related to decreased INS0-60/GLC0-60 (r = -0.71, p < 0.001), fasting insulin (r = -0.71, p < 0.001), and insulin AUC (r = -0.85, p < 0.001). CONCLUSION: Seven weeks of PRT increases insulin sensitivity and reduces glucose-stimulated insulin secretion in NBF, but not HBF women. Obesity attenuates exercise-induced improvements in glucose regulation in young non-diabetic women.

Interpreting normalized and nonnormalized data after acute static stretching in athletes and nonathletes.

The purpose of this study was to determine the effect of acute static stretching on torque and electromyography (EMG) in female athletes (ATHs) and nonathletes (NONATHs) using both normalized (NORM) and nonnormalized (NONNORM) data. Fifteen ATHs recruited from women's National Collegiate Athletic Association Division II varsity basketball and volleyball teams were paired to 14 NONATHs. Electromyography (microV) was detected over the rectus femoris during isokinetic leg extensions at 60 and 300 degrees .s before (PRE) and after (POST) static stretching. There was a significant main effect for torque (mean +/- SD PRE = 81.9 +/- 22.7 Nxm; POST = 77.0 +/- 21.9 Nxm) and EMG amplitude (PRE = 767.6 +/- 288.6 microV; POST = 664.2 +/- 219.3 microV) for PRE compared to POST. For the NORM data, there was a significant decrease in torque for the NONATHs (mean +/- SD PRE = 73 +/- 12 Nxm; POST = 67 +/- 12 Nxm) but no significant difference for the ATHs (mean +/- SD PRE = 65 +/- 11 Nxm; POST = 66 +/- 8 Nxm). The NONNORM data indicated that both the ATHs and NONATHs displayed a stretching-induced decrease in torque that may be manifested in a decreased ability to activate the muscle. The NORM data revealed the NONATHs but not the ATHs were hindered in their ability to produce torque as a result of the stretching. Coaches and ATHs may want to carefully consider whether to include stretching in their precompetition routine. When reading the literature, the practitioner should consider the manner in which the data were calculated and analyzed (NORM or NONNORM) because it may affect the conclusions of the study.

Effects of low- and high-volume stretching on bench press performance in collegiate football players.

The purpose of this study was to determine the effects of acute low- and high-volume static and proprioceptive neuromuscular facilitation (PNF) stretching on 1-repetition maximum (1RM) bench press. Fifteen healthy male National Collegiate Athletic Association Division II football players (age: 19.9 +/- 1.1 years; weight: 98.89 +/- 13.39 kg; height: 184.2 +/- 5.7 cm; body composition: 14.6 +/- 7.4%; and 1RM bench press: 129.7 +/- 3.3 kg) volunteered to participate in the study. Subjects completed 5 different stretching protocols integrated with a 1RM dynamic warm-up routine followed by 1RM testing in randomly assigned order. The protocols included (a) nonstretching (NS), (b) low-volume PNF stretching (LVPNFS), (c) high-volume PNF stretching (HVPNFS), (d) low-volume static stretching (LVSS), and (d) high-volume static stretching (HVSS). Two and 5 sets of stretching were completed for the low- and high-volume protocols, respectively. The stretching protocols targeted triceps and chest/shoulder muscle groups using 2 separate exercises. There were no significant differences in 1RM bench press performance (p > 0.05) among any of the stretching protocols NS (129.7 +/- 3.3 kg), LVPNFS (128.9 +/- 3.8 kg), HVPNFS (128.3 +/- 3.7 kg), LVSS (129.7 +/- 3.7 kg), and HVSS (128.2 +/- 3.7 kg). We conclude that low- and high-volume PNF and static stretching have no significant acute effect on 1RM bench press in resistance-trained collegiate football players. This suggests that resistance-trained athletes can include either (a) a dynamic warm-up with no stretching or (b) a dynamic warm-up in concert with low- or high-volume static or PNF flexibility exercises before maximal upper body isotonic resistance-training lifts, if adequate rest is allowed before performance.

The effect of glycerol on torque, electromyography, and mechanomyography.

The purpose of this investigation was to determine the effect of hyperhydration on the electromyographic (EMG) and mechanomyographic (MMG) responses during isometric and isokinetic muscle actions of the biceps brachii. Eight (22.1 +/- 1.8 years, 79.5 +/- 22.8 kg) subjects were tested for maximal isometric, submaximal isometric, and maximal concentric isokinetic muscle strength in either a control (C) or hyperhydrated (H) state induced by glycerol ingestion while the EMG and MMG signals were recorded. Although fluid retention was significantly greater during the H protocol, the analyses indicated no change in torque, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, or MMG MPF with hyperhydration. These results indicated that glycerol-induced fluid retention does not affect the torque-producing capabilities of a muscle, the impulses (EMG) going to a muscle, or muscular vibrations (MMG). It has been suggested that EMG and MMG can be used as direct electrical/mechanical monitoring, which could be presented to trainers and athletes; however, before determining the utility of these signals, the MMG and EMG responses should be examined under a variety of conditions such as in the present study.