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Specificity and transfer of lower-body strength: influence of bilateral or unilateral lower-body resistance training

Appleby, BB, Cormack, SJ, and Newton, RU. Specificity and transfer of lower-body strength: Influence of bilateral or unilateral lower-body resistance training. J Strength Cond Res 33(2): 318-326, 2019-To examine the development of lower-body strength using either bilateral or unilateral resistance training. Developmental rugby players (n = 33; mean training age = 5.4 ± 2.9 years; 1 repetition maximum [1RM] 90° squat = 178 ± 27 kg) completed an 18-week randomized controlled training design (bilateral group [BIL], n = 13; unilateral group [UNI], n = 10; comparison, n = 10). The 8-week training phase involved 2 lower-body, volume-load matched resistance sessions per week (6-8 sets × 4-8 reps at 45-88% 1RM), differing only in the prescription of a bilateral (back squat) or unilateral (step-up) resistance exercise. Maximum strength was assessed by a randomized order of 1RM back squat and step-up testing and analyzed for within- and between-group differences using effect sizes (ES ± 90% confidence limits [CL]). Both training groups showed practically important improvements in their trained exercise (ES ± 90% CL: BIL = 0.67 ± 0.48; UNI = 0.74 ± 0.38) with transfer to their nontrained resistance exercise (BIL step-up = 0.27 ± 0.39: UNI squat = 0.42 ± 0.39). The difference between groups in adaptation of squat strength was unclear (BIL ES = -0.34 ± 0.55), while the UNI group showed an advantage in step-up training (ES = 0.41 ± 0.36). The results demonstrate that practically important increases in lower-body strength can be achieved using bilateral or unilateral resistance training and development of that strength may be expressed in the movement not trained, supporting the transfer of strength training between exercises of similar joint movements and muscles. Coaches may choose to incorporate unilateral strength training where the prescription of bilateral training may be inhibited

Unilateral and bilateral lower-body resistance training does not transfer equally to sprint and change of direction performance

Given maximal strength can be developed using bilateral or unilateral resistance training, the purpose of this study was to determine the magnitude of transfer of unilateral or bilateral resistance training to sprint and change of direction (COD) performance. Thirty-three trained participants (average training age = 5.4 ± 2.9 years and 1 repetition maximum [1RM] 90° squat = 177.6 ± 26.7 kg) completed either a bilateral group (BIL, n = 13), unilateral (UNI, n = 10), or comparison (COM, n = 10) 18-week randomized controlled training design. Training involved 2 lower-body, volume-load-matched resistance sessions per week (6-8 sets × 4-8 reps at 45-88% 1RM), differing only in the prescription of a bilateral (squat) or unilateral (step-up) resistance exercise. Strength was assessed through 1RM squat and step-up, in addition to 20-m sprint and a customized 50° COD test. The effect size statistic ± 90% confidence limit (ES ± CL) was calculated to examine the magnitude of difference within and between groups at each time point. BIL and UNI groups improved their trained and nontrained strength exercise with an unclear difference in adaptation of squat strength (ES = -0.34 + 0.55). Both groups improved 20-m sprint (ES: BIL = -0.38 ± 0.49 and UNI = -0.31 ± 0.31); however, the difference between the groups was unclear (ES = 0.07 ± 0.58). Although both groups had meaningful improvements in COD performance, bilateral resistance training had a greater transfer to COD performance than unilateral resistance training (between-groups ES = 0.59 ± 0.64). Both bilateral and unilateral training improved maximal lower-body strength and sprint acceleration. However, the BIL group demonstrated superior improvements in COD performance. This finding potentially highlights the importance of targeting the underlying physiological stimulus that drives adaptation and not exercise selection based on movement specificity of the target performance

Kinetics and kinematics of the squat and step-up in well-trained rugby players

The purpose of this study was to compare and contrast the kinetics and kinematics of squat and step-up performance in well-trained athletes. Triaxial ground reaction force (GRF) and 3D kinematic data were collected in 4 maximal effort repetitions each at 70, 80, and 90% of 1 repetition maximum (1RM) of squat and step-up. The difference in concentric phase kinetics and kinematics between the squat and step-up was compared using effect sizes (ES ± 90% confidence limits [CLs]) classified as: less than 0.2 as trivial; 0.2-0.6 as small; 0.6-1.2 as moderate; and 1.2-2.0 as large. Where the 90% CL crossed negative and positive 0.2 values, the effect was considered unclear.n Ground reaction force was higher for the step-up than squat at all relative intensities per leg (peak GRF ES: 2.56 ± 0.19 to 2.70 ± 0.37; average GRF ES: 1.45 ± 0.27 to 1.48 ± 0.29). Per leg, the difference in concentric impulse favored the step-up compared with squat at 70% 1RM (ES = 0.71 ± 0.40) and 80% 1RM (ES = 0.30 ± 0.41) but was unclear at 90% 1RM (ES = -0.25 ± 0.47). The squat peak velocity was greater compared with step-up at all intensities (ES = -1.74 ± 0.48 to -1.33 ± 0.48). Despite a lower external load and a single base of support, per leg, the step-up produced comparable GRF because the squat suggesting overload provided by the step-up is sufficient for maximal strength development. Future research may investigate the efficacy of the step-up in a training intervention for the development of lower-body strength

Reliability of squat kinetics in well-trained rugby players: Implications for monitoring training

The aim of this study was to determine the within-session reliability in kinetic variables of the squat in well-trained athletes during a typical resistance training protocol. Fifteen subjects completed 2 testing sessions. Session 1 was establishment of 1 repetition maximum (1RM) squat, and session 2 involved 2 sets of 2 maximal effort repetitions of the squat at 70, 80, and 90% of 1RM with 3D motion analysis and ground reaction force (GRF) measurement using 2 in-ground triaxial force plates. Reliability was calculated using typical error ± 90% confidence limits, expressed as the coefficient of variation and intraclass correlation coefficient. The smallest worthwhile change (SWC%), calculated as 0.2 × between-subject SD, was used to determine the smallest important change in performance. Peak GRF and average GRF were found to have acceptable measures of reliability with the combined left and right leg average GRF capable of detecting the SWC. Independent limb contributions were reliable (left and right, or dominant and nondominant). Reliable kinetics can be obtained in back squat performance typical of a resistance training session in well-trained athletes. This suggests that coaches integrating force plate technology within training sessions may effectively capture between 1 and 6 training sets among several athletes, facilitating analysis and intervention on larger data sets

Fermi Surface as the Driving Mechanism for Helical Antiferromagnetic Ordering in Gd-Y Alloys

The first direct experimental evidence for the Fermi surface (FS) driving the helical antiferromagnetic ordering in a gadolinium-yttrium alloy is reported. The presence of a FS sheet capable of nesting is revealed, and the nesting vector associated with the sheet is found to be in excellent agreement with the periodicity of the helical ordering.Comment: 4 pages, 4 figure

A deterministic method for particle sorting by dynamic acoustic fields

This paper investigates the dynamic acoustic sorting method from a theoretical perspective. Analytical equations of motion and numerical simulations have been used to optimize parameters for sorting various particle mixtures. The effect of changes in field parameters as frequency or voltage on efficient sorting has been investigated. Experiments have been carried out to verify theoretical findings

Developing young people's sense of self and place through sport

Previous research has recognized positive health implications, both physical and mental, as an outcome of participation in leisure pursuits. They provide opportunities for self-expression and stress reduction, as well as an environment in which people can socialize. Leisure activities, specifically sport activities, can play a significant role in young people's identity development. This paper explores the leisure activities in which young people in Adelaide, Australia participate. It examines the role of leisure activities in terms of young people's identity and feelings towards their hometown. This study consisted of semi-structured focus groups conducted with 24 senior high school students, followed by a survey resulting in 226 useable responses. Respondents were aged between 16 and 18 years of age. From the range of activities identified and explored, the results revealed sports activities to have the greatest impact on young people's lives. The results demonstrated that frequency of participation has a significant effect on young people's involvement levels and how they identify with the activity