Test-Retest Reliability Between Free Weight and Machine-Based Movement Velocities.

Miller, RM, Freitas, EDS, Heishman, AD, Koziol, KJ, Galletti, BAR, Kaur, J, and Bemben, MG. Test-retest reliability between free weight and machine-based movement velocities. J Strength Cond Res 34(2): 440-444, 2020-Several devices are available to measure muscular power through velocity measurement, including the Tendo FitroDyne. The ability for such devices to produce consistent results is still questioned, and the reproducibility of measurement between free weight and machine exercise has yet to be examined. Therefore, the aim of this investigation was to determine the test-retest reliability for barbell velocity during the bench press (BP) and weight velocity during the 2 leg press (2LP) for loads corresponding to 20-80% of 1 repetition maximum (1RM). Forty recreationally active individuals (22.6 ± 2.5 years; 175.9 ± 10.8 cm; and 76.2 ± 13.2 kg) with a 1RM BP and 2LP of 66.8 ± 32.4 kg and 189.5 ± 49 kg, respectively, volunteered for this study. Subjects completed 1 familiarization visit preceding 3 testing visits, which encompassed 1RM determination and 2 days of velocity testing. Forty-eight hours after 1RM testing, the subjects performed 1 repetition at 20, 30, 40, 50, 60, 70, and 80% of their 1RM for each exercise in randomized order. Subjects returned to the laboratory 1 week later to perform the velocity assessment again in randomized order. Intraclass correlation coefficient (ICC2,1) and relative SEM for the BP and 2LP ranged from 0.56 to 0.98 (3-18.1%) and 0.78 to 0.98 (2.8-7.2%), respectively, and no mean differences were observed between trials. The results suggest high reliability for BP velocity between 30 and 60% 1RM and moderate reliability at 20, 70, and 80% 1RM, while the 2LP displayed high to excellent reliability from 20 to 80% 1RM. Cumulatively, machine-based exercise displayed greater reproducibility; however, additional machine exercises need to be examined to bolster this conclusion.

Maximal power production as a function of sex and training status.

Maximal muscular power is achieved at lower percentages of maximal strength (1RM); however, this notion has not been elucidated based on sex or training status. Therefore, the purpose of this investigation was to examine the influence of sex and training status on maximal power production. Sixty men and women (resistance trained or untrained) completed 1RM testing for the two-leg press (2LP) and bench press (BP). Participants then returned to perform single repetitions at 20, 30, 40, 50, 60, 70 and 80% of their 1RM to determine muscular power. Factorial analyses determined significant interactions (training status by sex by intensity) for the BP (F=35.6, p<0.001) and 2LP (F=8.2, p<0.001). Subsequent analyses indicated that during the BP trained men produce maximal power between 30-40% 1RM compared to untrained men at 60-70% 1RM. Trained women produced maximal power at 50% 1RM compared to untrained women at 60-70% 1RM. During the 2LP, trained men produced maximal power at 40% 1RM compared to untrained men at 60% 1RM. Trained women produced maximal power at 50% 1RM compared to 60-70% 1RM in untrained women. These data suggest that resistance trained individuals and men display maximal power at a lower relative intensity than untrained individuals and women.

The Acute Physiological Responses to Traditional vs. Practical Blood Flow Restriction Resistance Exercise in Untrained Men and Women.

This study compared the acute physiological responses of traditional and practical blood flow restriction resistance exercise (tBFR and pBFR, respectively) and high- and low-load resistance exercise without BFR (HL and LL, respectively), as well as the potential sex differences within the aforementioned exercise methods. Fourteen men and fifteen women randomly completed the following experimental conditions: (1) tBFR, consisting of four sets of 30-15-15-15 repetitions of the bilateral horizontal leg press and knee extension exercises, at 30% of one-repetition maximum (1-RM), with a 13.5 cm wide pneumatic cuff placed at the most proximal portion of each thigh and inflated to a pressure equivalent to 50% of the participant's total occlusion pressure; (2) pBFR, which was the same as the tBFR condition, except that an elastic band wrapped around the proximal portion of each thigh at a tightness of 7 on a 0 to 10 perceived pressure scale was used to reduce blood flow; (3) LL, same as the tBFR and pBFR protocols, except that no BFR was applied; and (4) HL, consisting of 3 sets of 10 repetitions at 80% of 1-RM, with the same 1-min rest interval between sets and a 3-min rest period between exercises. At baseline, immediately post-, 5 min post-, and 15 min post-exercise, whole-blood lactate (WBL), indices of muscle swelling (muscle thickness and thigh circumference), hematocrit and plasma volume changes, were measured as well as superficial electromyography (sEMG) amplitude during exercise. There were no significant (p > 0.05) differences between the tBFR and pBFR exercise protocols for any of the physiological parameters assessed. However, significantly greater (p < 0.05) WBL and sEMG values were observed for HL compared to the remaining exercise conditions. Finally, males displayed greater WBL levels than females at 15 min post-exercise. Interestingly, males also displayed significantly (p < 0.05) greater sEMG amplitude than females within the low-load trials during leg press, but no significant (p < 0.05) sex differences were observed during knee extension. In conclusion, tBFR and pBFR seemed to be capable of inducing the same acute physiological responses. Furthermore, males displayed greater responses than females for some of the physiological parameters measured.

Perceptual responses: Clinical versus practical blood flow restriction resistance exercise.

The purpose of the current investigation was to compare the acute perceptual responses during low-load resistance exercise (RE) with clinical blood flow restriction (cBFR-RE) and practical blood flow restriction (pBFR-RE), and during conventional low- (LL-RE) and high-load resistance exercise (HL-RE), to determine if these responses differed between young males and females. Twenty-nine participants (14 males: 23.6±2.7years, 25.3±3.1kg/m2 and 15 females: 20.3±1.6years, 23.4±1.9kg/m2) completed the following exercise conditions in a randomized design: 1) cBFR-RE, 2) pBFR-RE, 3) HL-RE, and 4) LL-RE. Low-load conditions consisted of 30-15-15-15 repetitions of two-leg press (LP) and knee extension (KE) exercises with 30% one-repetition maximum (1-RM), and HL-RE consisted of 3 sets of 10 repetitions at 80% 1-RM, all with 60s rest intervals. Ratings of perceived exertion (RPE) and discomfort were assessed before exercise and immediately following each set. RPE was significantly higher in HL-RE compared to all low-load conditions for both exercises after each set (all p<0.05). cBFR-RE resulted in significantly greater RPE than pBFR-RE and LL-RE for both exercises for sets 1-4 for LP and sets 2-3 for KE (all p<0.05). Levels of discomfort were similar between cBFR-RE and HL-RE, which tended to be significantly higher than pBFR-RE and LL-RE (p<0.05). Men reported significantly greater RPE than women following sets 2-4 during KE with cBFR-RE and sets 2 and 3 during KE for HL-RE (all p<0.05). Males also reported significantly greater discomfort than women following sets 2-4 for KE LL-RE (p<0.05). Altogether, these data suggest that pBFR-RE may provide a more favorable BFR condition based on perceptual responses and that perceptual responses may differ between sexes across varying resistance exercise conditions.