The purpose of this study was to determine the effect of an acute static stretching bout of the biceps brachii on torque, electromyography (EMG), and mechanomyography (MMG) during concentric isokinetic muscle actions. Eighteen (men, n ϭ 10; women, n ϭ 8) adult subjects (M Ϯ SD age ϭ 22.7 Ϯ 2.8 years; weight ϭ 78.0 Ϯ 17.0 kg; height ϭ 177.9 Ϯ 11.0 cm) performed maximal isokinetic (30 and 270Њ·s Ϫ1 ) forearm flexion strength testing on 2 occasions while EMG and MMG were recorded. Subjects were randomly assigned to stretching (STR) or nonstretching (NSTR) protocols before strength testing. Two-way ANOVAs with repeated measures revealed significantly (p Յ 0.05) greater torque for NSTR (M Ϯ SEM ϭ 36.9 Ϯ 3.3 N·m) vs. STR (35.2 Ϯ 3.3 N·m), significantly greater MMG amplitude for STR vs. NSTR for 30Њ·s Ϫ1 (STR ϭ 93.5 Ϯ 14.4 mV; NSTR ϭ 63.1 Ϯ 10.6 mV) and 270Њ·s Ϫ1 (STR ϭ 207.6 Ϯ 35.6 mV; NSTR ϭ 136.4 Ϯ 31.7 mV), and no difference in EMG amplitude. These results indicate that a greater ability to produce torque without prior stretching is related to the musculotendinous stiffness of the muscle rather than the number of motor units activated. This suggests that performing activities that reduce muscle stiffness (such as stretching), may be detrimental to performance. Key Words: autogenic inhibition, musculotendinous stiffness, acuteReference Data: Evetovich, T.K., N.J. Nauman, D.S. Conley, and J.B. Todd. Effect of static stretching of the biceps brachii on torque, electromyography, and mechanomyography during concentric isokinetic muscle actions.

The purpose of this study was to determine the effect of postactivation potentiation (PAP)-inducing activities in 4 separate studies examining vertical (VJP) and horizontal (HJP) jump performance, shot put performance (SPP), and sprint performance (SP), in National Collegiate Athletic Association Division II athletes. Study 1: 12 male (mean ± SD; age = 20.2 ± 2.0 years; height = 178.1 ± 6.2 cm; weight = 73.3 ± 6.43 kg) and 8 female (age = 20.1 ± 1.0 years; height = 169.6 ± 5.5 cm; weight = 59.8 ± 7.6 kg) track athletes participated in HJP and VJP testing before and after performing a parallel back squat (PBS) at 85% 1 repetition maximum (RM). Study 2: 10 (6 men and 4 women) shot put throwers (age = 20.6 ± 0.7 years; height = 182.1 ± 9.8 cm; weight = 102.8 ± 23.6 kg) participated in SPP testing for control (C), 3RM bench press, and 3RM PBS protocols. Study 3: 7 football players (age = 20.4 ± 1.6 years; weight = 87.8 ± 8.3 kg; height = 184.3 ± 7.2 cm) participated in SP testing before (PBS1) and after (PBS2) performing a 3RM PBS. Study 4: 11 football players (age = 20.3 ± 1.8 years; height = 180.6 ± 7.5 cm; weight = 86.1 ± 12.8 kg) participated in VJP testing for C and 3RM PBS protocols. Results of study 1: There was a significant (p ≤ 0.05) increase in VJP (PRE = 61.9 ± 12.3 cm; POST = 63.6 ± 11.6 cm) and HJP (PRE = 93.7 ± 11.0 cm; POST = 95.9 ± 11.5 cm). Study 2: SPP after PBS (11.67 ± 1.92 m) was not different vs. C (11.77 ± 1.81), but bench press (11.91 ± 1.81 m) was significantly greater (p ≤ 0.05) than both PBS and C. Study 3: SP time was significantly lower for PBS2 (4.6014 ± 0.17995 seconds) vs. PB1 (4.6557 ± 0.19603 seconds). Study 4: There was no difference in VJP for C (68.35 ± 2.16 cm) vs. PBS (68.12 ± 2.51 cm). Our data show that a 3RM PBS resulted in significant improvements in VJP, HJP, SPP, and SP in National Collegiate Athletic Association Division II male and female athletes. Strength and conditioning practitioners should potentially alter their warm-up programs to include PAP protocols to enhance performance of power athletes. However, there were nonresponders in each study, and coaches and athletes need to determine whether it is worthwhile to identify nonresponders before implementing PAP protocols.

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The purpose of this study was to determine the effect of an acute static stretching bout of the biceps brachii on torque, electromyography (EMG), and mechanomyography (MMG) during concentric isokinetic muscle actions. Eighteen (men, n ϭ 10; women, n ϭ 8) adult subjects (M Ϯ SD age ϭ 22.7 Ϯ 2.8 years; weight ϭ 78.0 Ϯ 17.0 kg; height ϭ 177.9 Ϯ 11.0 cm) performed maximal isokinetic (30 and 270Њ•s Ϫ1) forearm flexion strength testing on 2 occasions while EMG and MMG were recorded. Subjects were randomly assigned to stretching (STR) or nonstretching (NSTR) protocols before strength testing. Two-way ANOVAs with repeated measures revealed significantly (p Յ 0.05) greater torque for NSTR (M Ϯ SEM ϭ 36.9 Ϯ 3.3 N•m) vs. STR (35.2 Ϯ 3.3 N•m), significantly greater MMG amplitude for STR vs. NSTR for 30Њ•s Ϫ1 (STR ϭ 93.5 Ϯ 14.4 mV; NSTR ϭ 63.1 Ϯ 10.6 mV) and 270Њ•s Ϫ1 (STR ϭ 207.6 Ϯ 35.6 mV; NSTR ϭ 136.4 Ϯ 31.7 mV), and no difference in EMG amplitude. These results indicate that a greater ability to produce torque without prior stretching is related to the musculotendinous stiffness of the muscle rather than the number of motor units activated. This suggests that performing activities that reduce muscle stiffness (such as stretching), may be detrimental to performance.

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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 purposes of this study were to validate the 12-min swim as a field test of VO2 peak in female recreational swimmers and to compare its validity with that of the 12-min run. The results are contrasted with those previously reported on a comparable group of male recreational swimmers. Thirty-four young women completed 12-min swim, 12-min run, tethered swimming VO2 peak, and treadmill running VO2 peak tests within 3 weeks. Mean (+/- SD) 12-min swim and run distances were 597 +/- 82 and 2,313 +/- 317 m, and mean tethered swim and treadmill run VO2 peak values were 39.2 +/- 4.9 and 45.4 +/- 6.3 ml.kg BW-1.min-1, respectively. Correlation coefficients and standard errors of estimate for predictions of swimming VO2 peak from the 12-min swim (.42 and 4.5 ml.kg BW-1.min-1) and run (.58 and 4.1 ml.kg BW-1.min-1) and for predictions of treadmill run VO2 peak from the 12-min swim (.34 and 6.0 ml.kg BW-1.min-1) and run (.87 and 3.2 ml.kg BW-1.min-1) indicated that the 12-min run was a more accurate predictor of tethered swim or treadmill run VO2 peak than the 12-min swim. These data are in close agreement with our previous study on young male recreational swimmers. We conclude that the 12-min swim has relatively low validity as a field test of peak aerobic power and that it is not an equally valid alternative to the 12-min run in young adult female recreational swimmers.(ABSTRACT TRUNCATED AT 250 WORDS)

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