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The aim of this study was to assess the agreement of three different automated methods of identifying force-onset (40 N, 5 SDs, and 3 SDs) with manual identification, during the isometric mid-thigh pull (IMTP). Fourteen resistance-trained participants with >6 months experience training with the power clean volunteered to take part. After three familiarisation sessions, the participants performed five maximal IMTPs separated by 1 min of rest. Fixed bias was found between 40 N and manual identification for time at force-onset. No proportional bias was present between manual identification and any automated threshold. Fixed bias between manual identification and automated was present for force at onset and F150. Proportional but not fixed bias was found for F50 between manual identification and all automated thresholds. Small to moderate differences (Hedges g = −0.487- −0.692) were found for F90 between all automated thresholds and manual identification, while trivial to small differences (Hedges g = −0.122—−0.279) were found between methods for F200 and F250. Based on these results, strength and conditioning practitioners should not use a 40 N, 5 SDs, or 3 SDs threshold interchangeably with manual identification of force-onset when analysing IMTP force–time curve data. [ABSTRACT FROM AUTHOR]

Isometric strength training has been reported to benefit various sport-related dynamic performances. However, it is still unknown whether performing isometric strength training at single or multiple joint angles would elicit greater benefit. Purpose: To compare the effects of isometric bench press performed at single (SIBP) and multiple (MIBP) joint angles on dynamic strength and overhead throwing performance. Methods: Sixteen male softball and baseball athletes performed overhead throwing, 1-repetition-maximum (1RM) bench press, and ballistic push-up during pretest and posttest. They were then randomly assigned to either SIBP or MIBP to undergo 12 strength training sessions. During the training, isometric bench press was performed at only 90° elbow angle for SIBP but at 60°, 90°, and 120° elbow angles for MIBP. Results: A significant main time effect was observed for bench press 1RM (P =.003) and relative 1RM (P <.001). Similarly, a significant main time effect was observed for ballistic push-up peak power only (P =.037). There was no significant change in overhead throwing velocity in either group. There was also no significant difference in change in all measures between groups. However, a moderate effect in favor of MIBP was observed for change in ballistic push-up peak power (P =.180, g = 0.67). Conclusions: Based on the current findings, the inclusion of both SIBP and MIBP were equally beneficial to maximal strength development. However, performing MIBP had a greater effect on power development. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the peak force (PF), peak power (PP), and peak velocity (PV) outputs produced during half-squat (HS) and jump squat (JS) exercises executed at 20, 40, 60, and 80% of 1 repetition maximum (1RM) in the HS (HS 1RM) and to compute and compare the strength deficit (SDef) achieved in these exercises across these loads. Twenty-four national rugby union players (age: 25.7 ± 3.6 years) performed HS 1RM and a progressive loading test in the HS and JS exercises. The PF, PP, and PV values were obtained in all loads for both exercises, and the SDef was calculated as the percentage difference between the PF at distinct relative intensities and the PF at HS 1RM. The differences in HS and JS variables were determined using an analysis of variance with repeated measures. Higher PF, PP, and PV outputs were generated in the JS in comparison with the HS exercise (p < 0.05); moreover, the SDef magnitudes were significantly lower in the JS (p < 0.01), for all loading conditions. Importantly, the differences in SDef, and as a consequence, PF, PP, and PV decreased progressively with increasing load. Overall, the loaded JS exhibited increased levels of PF, PP, and PV and reduced levels of SDef when compared to the traditional HS performed across a range of loads. The JS is indicated to reduce the SDef and improve the athletes’ ability to apply force at higher velocities. Nevertheless, with heavier loads (i.e.,≥80% HS 1RM), its potential advantages and effectiveness may be seriously compromised. [ABSTRACT FROM AUTHOR]

The purposes of this study were to investigate the acute effects of resistance training protocol on kinetic changes in squat jump (SJ), shortened isometric mid-thigh pull (IMTP), and isometric squat (ISQ) and to examine the relationship of dynamic maximum strength with performance changes over 48 hours in resistance-trained individuals. Participants completed performance tests at pre-, post-24 hours, and post-48 hours resistance training protocol (Baseline, Post24, and Post48). The training protocol consisted of 5 sets of 10 repetitions of back squat (BSQ) at 60% of 1 repetition maximum (1RM). SJ variables included jump height (JH), peak power (PP), and relative PP. For the IMTP and ISQ, isometric peak force (IPF), relative IPF, rate of force development at 250 milliseconds (RFD250), and impulse at 250 milliseconds (IMP250) were calculated. Significant decreases were observed from Baseline to Post24 (p = 0.023, Cohen's dz effect size [dz] = 1.00) and Post48 (p = 0.032, dz = 0.94) in SJ JH. IMTP IMP250 significantly decreased from Baseline to Post48 (p = 0.046, dz = 0.88). Significant negative correlation was found between relative 1RM BSQ and the changes from Baseline to Post48 in ISQ RFD250 (p = 0.046,r = −0.61). Acute performance decreases might remain until 48 hours after resistance training in explosive strength and impulse regardless of isometric testing type. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the association between hamstring muscle peak torque and rapid force capacity (rate of torque development, RTD) vs sprint performance in elite youth football players. Methods: Thirty elite academy youth football players (16.75 [1.1] y, 176.9 [6.7] cm, 67.1 [6.9] kg) were included. Isometric peak torque (in Newton meters per kilogram) and early- (0–100 ms) and late- (0–200 ms) phase RTD (RTD100, RTD200) (in Newton meters per second per kilogram) of the hamstring muscles were obtained as independent predictor variables. Sprint performance was assessed during a 30-m-sprint trial. Mechanical sprint variables (maximal horizontal force production [FH0, in Newtons per kilogram], maximal theoretical velocity [V0, in meters per second], maximal horizontal power output [Pmax, in watts per kilogram]) and sprint split times (0–5, 0–15, 0–30, and 15–30 m, in seconds) were derived as dependent variables. Subsequently, linear-regression analysis was conducted for each pair of dependent and independent variables. Results: Positive associations were observed between hamstring RTD100 and FH0 (r2 =.241, P =.006) and Pmax (r2 =.227, P =.008). Furthermore, negative associations were observed between hamstring RTD100 and 0- to 5-m (r2 =.206, P =.012), 0- to 15-m (r2 =.217, P =.009), and 0- to 30-m sprint time (r2 =.169, P =.024). No other associations were observed. Conclusions: The present data indicate that early-phase (0–100 ms) rapid force capacity of the hamstring muscles plays an important role for acceleration capacity in elite youth football players. In contrast, no associations were observed between hamstring muscle function and maximal sprint velocity. This indicates that strength training focusing on improving early-phase hamstring rate of force development may contribute to enhance sprint acceleration performance in this athlete population. [ABSTRACT FROM AUTHOR]

Purpose: To compare the associations between optimum power loads and 1-repetition-maximum (1RM) values (assessed in half-squat and jump-squat exercises) and multiple performance measures in elite athletes. Methods: Sixty-one elite athletes (15 Olympians) from 4 different sports (track and field [sprinters and jumpers], rugby sevens, bobsled, and soccer) performed squat and countermovement jumps, half-squat exercise (to assess 1RM), half-squat and jump-squat exercises (to assess bar-power output), and sprint tests (60 m for sprinters and jumpers and 40 m for the other athletes). Pearson product–moment correlation test was used to determine relationships between 1RM and bar-power outputs with vertical jumps and sprint times in both exercises. Results: Overall, both measurements were moderately to near perfectly related to speed performance (r values varying from −.35 to −.69 for correlations between 1RM and sprint times, and from −.36 to −.91 for correlations between bar-power outputs and sprint times; P <.05). However, on average, the magnitude of these correlations was stronger for power-related variables, and only the bar-power outputs were significantly related to vertical jump height. Conclusions: The bar-power outputs were more strongly associated with sprint-speed and power performance than the 1RM measures. Therefore, coaches and researchers can use the bar-power approach for athlete testing and monitoring. Due to the strong correlations presented, it is possible to infer that meaningful variations in bar-power production may also represent substantial changes in actual sport performance. [ABSTRACT FROM AUTHOR]

The purposes of this study were to investigate intrasession and intersession reliability of variables obtained from squat jump (SJ), shortened isometric midthigh pull (IMTP), and isometric squat (ISQ) protocols and to evaluate relationships between isometric and dynamic performance and 1 repetition maximum (1RM) back squat (BSQ). Eleven moderately resistance-trained men participated (27.8 ± 3.9 years; 175.0 ± 7.2 cm; 87.2 ± 11.4 kg). Subjects completed familiarization in the IMTP and ISQ, followed by 1RM BSQ at least 48 hours before the first performance test. Two performance tests occurred at 7-day intervals including SJ, IMTP, and ISQ. SJ variables included jump height (SJH), body mass (BM), peak force (PF), and peak power (PP). Isometric midthigh pull and ISQ variables included isometric peak force (IPF); relative IPF; rate of force development at 90, 200, and 250 milliseconds; and impulse at 90, 200, and 250 milliseconds. SJ, IMTP, and ISQ kinetic variables were considered reliable if intraclass correlations (ICCs) and coefficients of variations (CVs) were >0.80 and <10%. Intrasession and intersession reliability criteria were met for SJH, BM, PF, and PP (ICC = 0.91-1.00, CV = 0.5-9.1%). Isometric peak force and impulse at 200 and 250 milliseconds met intrasession and intersession reliability criteria for IMTP and ISQ (ICC = 0.90-0.99, CV = 2.1-8.1%). Significant large correlation was observed between 1RM BSQ and ISQ peak force (p = 0.038, r = 0.63), but not between 1RM BSQ and shortened IMTP peak force (p = 0.11, r = 0.50). Shortened IMTP and ISQ peak force and impulse are reliable kinetic variables, and ISQ peak force is indicative of 1RM BSQ in moderately resistance-trained men. [ABSTRACT FROM AUTHOR]

Kotani, Y, Lake, J, Guppy, SN, Poon, W, Nosaka, K, Hori, N, and Haff, GG. The reliability of the squat jump force-velocity and load-velocity profiles. J Strength Cond Res 36(11): 3000–3007, 2022—The purpose of this study was to investigate the between-session reliability of the squat jump force-velocity (FV) and load-velocity (LV) profiles. Eighteen subjects (age = 28.1 ± 4.8 years; height = 1.7 ± 9.7; body mass = 74.7 ± 12.8) who could back squat >1.5 times body mass participated in this study. Each subject completed a familiarization session, followed by 2 experimental sessions each separated by 72 hours. Subjects performed a series of squat jumps on a force plate against external loads between 0 and 100% of their body mass in a quasi-randomized block order. Intraclass correlation coefficient (ICC) and coefficient of variation (CV) were used to examine the between-session reliability. Peak velocity (PV) and mean velocity (MV) at each load were highly reliable (ICC >0.80, CV% <7.41, SEM <0.13 m·s−1, smallest detectable difference [SDD] <0.31 m·s−1, ES <0.21). Force-velocity profiles created with peak force and relative peak force resulted in poor to excellent reliability (ICC = 0.34–0.92, CV% = 11.9–26.3). When mean and relative mean forces were used to create FV profiles, there was poor to good reliability (ICC = 0.03–0.85, CV% = 18.1–39.4). When the LV profile was calculated with PV (ICC = 0.60–0.90, CV% = 7.9–16.9) or MV (ICC = 0.49–0.91, CV% = 11.1–23.4), there was poor to excellent reliability. There was no time effect found between sessions for both FV and LV profiles. The squat jump FV and LV profiles established with a force plate are not reliable. Therefore, these profiles are not recommended to be used to inform programming decisions. [ABSTRACT FROM AUTHOR]

Purpose: To examine the reliability and usefulness of the isometric midthigh pull (IMTP) and isometric squat (ISqT) performed at the same knee and hip angles. The scores produced in each test were compared to determine the magnitude of differences between tests. Methods: Twenty-six male and female athletes (age, 23.6 [4.3] y; height, 1.75 [0.07] m; and body mass, 68.8 [9.7] kg) performed 2 maximal repetitions of the IMTP and ISqT following a specific warm-up. Results: Maximum force, absolute peak force (PF), relative PF, allometrically scaled PF, rate of force development (0–200 and 0–250 ms), and impulse (0–300 ms) were deemed reliable (intraclass correlation coefficient [ICC] ≥.86 and coefficient of variation [CV] ≤9.4%) in the IMTP and ISqT based on predetermined criteria (ICC ≥.8 and CV ≤10%). Impulse (0–200 and 0–250 ms) was reliable in the ISqT (ICC ≥.92 and CV ≤9.9%). Participants produced significantly (P <.05) greater PF and impulse (0–300 ms) during the ISqT compared with the IMTP. When split by sex, female participants produced significantly greater PF (P =.042) during the ISqT, with no significant differences among male participants (P =.245). Both tests are capable of detecting changes in performance in maximum force and absolute PF. Conclusions: Both tests are reliable for non-time-dependent maximal strength measures when measured at the same knee and hip angles. The ISqT may be preferred when coaches want to test an athlete’s true maximum lower-limb strength, especially female athletes. [ABSTRACT FROM AUTHOR]

Loturco, I, McGuigan, MR, Rodríguez-Rosell, D, Pereira, LA, and Pareja-Blanco, F. A novel strategy to determine the 1-repetition maximum in the jump squat exercise. J Strength Cond Res 36(8): 2330–2334, 2022—This study aimed to determine the maximum relative load of the half-squat (HS; i.e., % HS 1-repetition maximum [1RM]) that can be used in its ballistic variation, namely, the jump squat (JS) exercise, and to examine whether this reference value varies in subjects with different strength levels. In total, 186 elite athletes from 10 distinct sport disciplines participated in this study. A progressive loading test up to HS 1RM was performed during the competitive phase of the season for all athletes. Mean propulsive velocity and propulsive phase duration were also assessed during the 1RM test. Athletes were divided into 3 distinct subgroups: "low," "middle," and "high" strength levels, based on their relative HS 1RM values (kg·kg−1). A 1-way analysis of variance was used to compare the variables assessed between the groups. Significance level was set at p < 0.05. The high group demonstrated the highest relative HS 1RM values, followed by the middle and low groups (all p < 0.05). No significant differences were observed between the groups for the remaining variables (p > 0.05). It was observed that at 86.0 ± 5.4% 1RM, the full concentric action can already be considered as entirely propulsive in the HS exercise for all subjects, independent of their strength levels. Therefore, this relative strength value may be used as a reference for the 1RM in the JS exercise. [ABSTRACT FROM AUTHOR]

This study investigated the effects of instantaneous performance feedback during the jump-squat exercise over a 6-week training period. Twenty-five strength-trained athletes were randomly divided into an instant feedback (n = 13, half-squat 3-repetition maximum (3RM)/ body mass = 2.38 6 0.19) or a nonfeedback (n = 12, halfsquat 3RM/body mass = 2.03 6 0.44) group. Both groups performed the same training program (3 3 week), consisting of 4 sets of 8 repetitions (weeks 1-3) and 8 sets of 4 repetitions (weeks 4-6) using a barbell with a load that maximized the average concentric power output (Pmax) of each athlete. Subjects in the instant feedback group were given real-time data after each repetition. Pre-, mid-, and post-training testing consisted of maximum 20-, 30-, and 50-m running speed, 3RM back half-squat load, Pmax and the load that maximized average concentric power output (Pmax load), countermovement jump (CMJ), and squat jump (SJ) height. Results revealed that the feedback group significantly improved all selected tests vs. nonfeedback (time 3 group interaction, p, 0.01). Significant improvements after training for 20, 30, 50 m, 3RM load, Pmax load, CMJ, and SJ were observed in the feedback group only (p, 0.01). Training without instant feedback did not lead to significant performance improvements; this group actually demonstrated significant decreases in SJ and Pmax (W) and Pmax load (p, 0.05). The results of this study indicate that the use of instant feedback during jump-squat training in athletes was beneficial for improving multiple performance tasks over 6 weeks of training. Instant feedback is an important element of power training to maximize adaptations when training strengthtrained athletes. [ABSTRACT FROM AUTHOR]

Sprinting represents a result-relevant task in many sports. The correlation of sprinting performance and one-repetition maximum (1RM) in a squat has been assumed as assured. Results of the correlation with 1RM of the plantar flexors are still pending. Assuming an increasing relevance of the reactive working capacity with increasing distance, a decrease of the influence of maximum strength of the calves is conceivable. We investigated the correlation of 1RM in a calf raise and sprint performance in consecutive sections up to 30 meters. The results showed medium to strong, very significant correlations (p < 0.01) for absolute (r = −0.483 to r = −0.720) and relative (r = −0.460 to −0.577) strength, whereas an increase of the correlation throughout the course is observed. The dynamic maximum strength of the calves is a basic prerequisite for short sprints and should be regarded as a performance reserve. [ABSTRACT FROM AUTHOR]

STUDY DESIGN: True experimental design. BACKGROUND: The back squat is an integral aspect of any resistance training program to improve athletic performance. It is also used for injury prevention of the lower limbs. OBJECTIVE: The purpose of this study was to examine the effect of back squat training at different intensities on strength and flexibility of the hamstring muscle group (HMG). METHODS: Twenty-two male recreational bodybuilders with at least two years of experience in resistance training were recruited to participate in a nine-week training program. They were randomly assigned to a heavy back squat group (90-95% of one repetition maximum) or a moderate-intensity back squat group (60-65% of one repetition maximum). RESULTS: The heavy back squat group resulted in a significantly (p < 0.001) increased in one repetition maximum strength but a significant (p < 0.001) reduction in HMG flexibility when compared to their counterparts. The results of the study indicate that while a heavy back squat training program is effective in improving strength, it has an adverse effect on the flexibility of the HMG. CONCLUSION: The implication of this study is that there is a tradeoff between strength and flexibility and trainers should select the appropriate training protocols for their athletes to maximize athletic performance. [ABSTRACT FROM AUTHOR]

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The article presents a study on the use of regression models to determine factors that affect an athlete's ability in jumping, sprinting, and changing direction. Topics include biomechanical variables, maximum strength tests, and the measurement of rate of force development (RFD) values. Anthropometric data and athletic performance are also discussed.

The article reports on research which was conducted to determine differences in anthropometric, body composition, physiological and neuromuscular markers between elite and amateur female wrestlers . Researchers evaluated 35 wrestlers. They found that the elite wrestlers had more fat free mass, maximum strength, peak power, grip strength and maximal muscle power than amateur wrestlers.