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Application of the ratings of perceived exertion-clamp model to examine the effects of joint angle on the time course of torque and neuromuscular responses during a sustained, isometric forearm flexion to task failure. J Strength Cond Res 37(5): 1023-1033, 2023-The present study used the ratings of perceived exertion (RPE)-clamp model during a sustained, isometric forearm flexion task to failure to determine the effects of joint angle on torque and neuromuscular responses. Twelve college-aged women performed two 3-second maximal voluntary isometric contractions at elbow joint angles (EJ) of 75˚, 100˚, and 125˚before sustained, isometric, forearm flexions anchored to RPE 5 7 to task failure (defined as RPE . 7, or the torque was reduced to zero) at EJ 75 , EJ 100 , and EJ 125 . The amplitude (AMP) and frequency (MPF) of the electromyographic (EMG) and mechanomyographic (MMG) signals from the biceps brachii were recorded. Repeated-measures ANOVAs and post hoc comparisons were used to examine differences across time and between joint angles for torque and neuromuscular parameters. A p-value #0.05 was considered significant. For each joint angle, there was a decrease (p , 0.05) in torque across the sustained, isometric task. Collapsed across joint angle, there were decreases (p , 0.001, h 2 p 5 0.378) in EMG AMP from 30 to 100% time to task failure. No changes were observed, however, for the other neuromuscular responses. The subjects voluntarily reduced torque to maintain RPE 5 7 for each joint angle, and we hypothesize that RPE was maintained by afferent feedback from group III/IV motor neurons and corollary discharge (efferent copy of an internal signal that develops from central motor commands). The RPE-Clamp Model may be extended to athletes recovering from injury because a self-selected exercise intensity may be perceived as more enjoyable and promote adherence.

Exercise-induced fatigability (EF) is defined as a fatigue-induced decline in force production and has been reported to exhibit mode-specific differences where unilateral (UL) tasks exhibit greater EF than bilateral (BL) tasks. While women have been reported to display a greater resistance to fatigue than men, few studies have examined whether women exhibit mode-specific differences in EF. Furthermore, few studies have examined the influence of EF on the bilateral deficit (BD). PURPOSE The purpose of the present study was to examine the patterns of responses for normalized isokinetic peak torque and the BD during fatiguing, maximal, isokinetic UL and BL leg extensions in women. METHODS Ten women (Mean ± SD; age = 20.9± 2.08 years; height = 170.4 ± 6.5 cm; body mass = 63.0 ± 7.1 kg) performed 50 UL and BL maximal, concentric, isokinetic leg extensions at 180°•s -1 on three separate visits. Each visit was characterized by a fatiguing task of 50 repetitions with either the dominant limb (DL), non-dominant limb (NL), or both limbs (BL) in random order. Isokinetic peak torque values were averaged across 5 consecutive repetitions and normalized to the value at repetition 5 for the respective fatiguing task. A bilateral deficit index (BDI) was quantified as: BDI = [100 × BL/ (NL + DL)] -100 with the absolute isokinetic peak torque values throughout the 50 repetitions. The mean differences for the normalized isokinetic peak torque values were examined with a 3 (Condition [BL, DL, NL]) × 10 (Repetition [5-50]) repeated measures (RM) ANOVA. The mean changes across repetitions for the BDI were examined with a 1 × 10 (Repetition [5-50]) RM ANOVA. RESULTS The 3 × 10 RM ANOVA demonstrated a significant (p < 0.01, η 2 p = 0.21) interaction with post-hoc analyses indicating an earlier decline in normalized peak torque for the DL (repetition 30) and NL (repetition 25) conditions than the BL (repetition 50) condition. The 1 × 10 RM ANOVA demonstrated no significant mean changes for the BDI (p = 0.05, η 2 p = 0.29). CONCLUSION These results indicated that the women exhibited a greater EF during UL compared to BL fatiguing, maximal, isokinetic leg extensions. While all participants exhibited a BD, there were no significant changes in the BD across the fatiguing task. Future studies are warranted to compare the mechanisms of task-specific EF between women and men.

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Background: Drop jumps (DJ) are commonly implemented in plyometric training programs in an attempt to enhance jump performance. However, it is unknown how different drop heights (DH) affect reactive strength index (RSI), jump height (JH) and ground contact time (GCT). Objectives: The purpose of this study was to assess the effect of various DHs on RSI, JH, and GCT. Methods: Twenty volunteers with a history of plyometric training (Males = 13, Females = 7; age: 22.80 ± 2.69 yr, height: 175.65 ± 11.81 cm, mass: 78.32 ± 13.50 kg) performed DJs from 30 cm (DJ30), 45 cm (DJ45), 60 cm (DJ60), 76 cm (DJ76), and 91 cm (DJ91) and a countermovement jump (0 cm). A 16-camera Vicon system was used to track reflective markers to calculate JH; a Kistler force plate was used to record GCT. RSI was calculated by dividing JH by GCT. RSI and GCT were compared using a 2x5 (sex x DH) mixed factor repeated measures ANOVA, while JH was compared using a 2x6 (sex x DH) repeated measures ANOVA. Results: There were no interactions, but there was a main effect for sex for both JH (M>F) and GCT (F>M). JH demonstrated no main effect for DH: DJ30 (0.49 ± 0.11 m), DJ45 (0.50 ± 0.11 m), DJ60 (0.49 ± 0.12 m), DJ76 (0.50 ± 0.11 m), and DJ91 (0.48 ± 0.12 m). However, GCT showed a main effect where DJ30 (0.36 ± 0.10 s), DJ45 (0.36 ± 0.12 s), and DJ60 (0.37 ± 0.10 s) were not significantly different but were less than DJ76 (0.40 ± 0.12 s) and DJ91 (0.42 ± 0.12 s). Conclusions: Increasing DH beyond 60 cm increased GCT but did not affect JH, resulting in decreased RSI. Therefore, practitioners designing plyometric training programs that implement DJs may utilize DHs up to 60 cm, thereby minimizing GCT without compromising JH.