Effect of Strength on Velocity and Power During Back Squat Exercise in Resistance-Trained Men and Women

The effects of fatigue on linear and angular kinematics during bilateral squat

This study was aimed to analyze in detail how the fatigue effects to kinematic parameters of body weight squat exercise (BSQ) by dividing a squat cycle into four different regions. Twenty-one male athletes participated in this study. Participants were divided into two groups according to their lower limb muscle ratio (LLMR). The BSQ was performed until participants were unable to continue the exercise due to the fatigue. Linear and angular kinematics were obtained by motion analysis software which has high validity and reliability. There was no significant but had large effect size interaction between fatigue conditions and LLMR groups in terms of knee ROM in the extension phase and hip angular velocity in braking phase of the flexion (0.08 > p >0.05, 0.18 > [Formula: see text] > 0.16). Fatigue condition did not have a significant effect on the duration in the acceleration and braking phases of BSQ (p > 0.05). There were many significant main effects on kinematics in the different regions due to the fatigue (0.01 < p <0.05, 0.44 > [Formula: see text] > 0.14). In the fatigue condition, there was a polynomial relationship between velocity of shoulder and hip joints (R2flex = 0.82, R2ext = 0.72) rather than linear (R2flex = 0.64, R2ext = 0.53) and coefficient correlations also decreased (rflex = 0.88 to 0.80, rext = 0.92 to 0.73). The sticking region was observed in the non-fatigue condition and disappeared when fatigue occurred. These results suggest that LLMR may be taken into consideration in the squat exercises, joint tracking may vary for velocity-based squat training and pre-test for sticking region observation may be apply with the BSQ.

A Systematic Review and Meta-Analysis of the Differences in Mean Propulsive Velocity between Men and Women in Different Exercises

The purpose of this paper was to conduct a systematic review and meta-analysis of studies examining the differences in the mean propulsive velocities between men and women in the different exercises studied (squat, bench press, inclined bench press and military press). Quality Assessment and Validity Tool for Correlational Studies was used to assess the methodological quality of the included studies. Six studies of good and excellent methodological quality were included. Our meta-analysis compared men and women at the three most significant loads of the force-velocity profile (30, 70 and 90% of 1RM). A total of six studies were included in the systematic review, with a total sample of 249 participants (136 men and 113 women). The results of the main meta-analysis indicated that the mean propulsive velocity is lower in women than men in 30% of 1RM (ES = 1.30 ± 0.30; CI: 0.99-1.60; p < 0.001) and 70% of 1RM (ES = 0.92 ± 0.29; CI: 0.63, 1.21; p < 0.001). In contrast, for the 90% of the 1RM (ES = 0.27 ± 0.27; CI: 0.00, 0.55), we did not find significant differences (p = 0.05). Our results support the notion that prescription of the training load through the same velocity could cause women to receive different stimuli than men.

Does resistance exercise lifting velocity change with different rest intervals?

BACKGROUND

In this study, we examined the sex difference of the effect of rest intervals on lifting velocity during resistance exercise.

METHODS

Twenty-two trained subjects (11 men and 11 women) were included. Each protocol consisted of 3 sets of 10 repetitions at 70% of 1- repetition maximum (1RM) with rest intervals of 90 s (R90), 150 s (R150), and 240 s (R240) in a crossover design. The exercise did parallel squats with free weights. The measurement items are lifting velocity (mean velocity) in each repetition and blood lactate concentration after exercise.

RESULTS

There was a significant interaction between changes in the average velocity of 10 repetition in each set (AV<inf>10rep</inf>) and sex in each protocol, indicating that AV<inf>10rep</inf> during squat exercise has decreased in men but not in women in each protocol (P=0.002-0.03).

CONCLUSIONS

Our results suggested that short rest intervals will not recover lifting velocity between short rest intervals until the next set at men, while women will be able to recover even with short rest intervals.

Acceleration and deceleration demands during training sessions in football: a systematic review

PURPOSE

The aim of this review is to summarize the current scientific knowledge about acceleration and deceleration demands during football training.

METHODS

A systematic search of three electronic databases (PubMed, SPORTDiscus, Web of Science) was performed to identify peer-reviewed relevant English-language articles, following PRISMA guidelines.

RESULTS

All acceleration and deceleration data were analyzed and organized into four categories: i) training drills variables (i.e. manipulated drills variables such as number of players in small-sided games), ii) training exercises (i.e. different drills such small games or circuit training), iii) players' positions (i.e. demands for each playing position) and iv) training schedule (i.e. training sessions presented as microcycles, season sections or full season). Full-text articles of 42 studies were included in the final analysis. Players' level included: amateur, youth, semi-professional, professional and elite players. All playing positions were considered, including goalkeepers. Six different global position systems brands were used, with the majority measuring data at 10 Hz. Different thresholds and intensities were used in several papers. Lower acceleration and deceleration intensities occurred more often than higher intensities in all four categories.

CONCLUSION

Different exercises elicit different demands and small-sided games presented higher acceleration and deceleration demands than circuit training and other running based drills. Furthermore, manipulating drills variables, as reducing or increasing number of players in small-sided games increase or decrease demands, respectively. Additionally, wide playing positions, such as fullbacks, are generally exposed to higher acceleration and deceleration demands. From a planning point of view, acceleration and deceleration demands decrease as match day approaches.

Velocity-based resistance training: do women need greater velocity loss to maximize adaptations?

Purpose

Men and women typically display different neuromuscular characteristics, force–velocity relationships, and differing strength deficit (upper vs. lower body). Thus, it is not clear how previous recommendations for training with velocity-loss resistance training based on data in men will apply to women. This study examined the inter-sex differences in neuromuscular adaptations using 20% and 40% velocity-loss protocols in back squat and bench press exercises.

Methods

The present study employed an 8-week intervention (2 × week) comparing 20% vs. 40% velocity-loss resistance training in the back squat and bench press exercises in young men and women (~ 26 years). Maximum strength (1-RM) and submaximal-load mean propulsive velocity (MPV) for low- and high-velocity lifts in squat and bench press, countermovement jump and vastus lateralis cross-sectional area were measured at pre-, mid-, and post-training. Surface EMG of quadriceps measured muscle activity during performance tests.

Results

All groups increased 1-RM strength in squat and bench press exercises, as well as MPV using submaximal loads and countermovement jump height (P < 0.05). No statistically significant between-group differences were observed, but higher magnitudes following 40% velocity loss in 1-RM (g = 0.60) and in low- (g = 1.42) and high-velocity (g = 0.98) lifts occurred in women. Training-induced improvements were accompanied by increases in surface EMG amplitude and vastus lateralis cross-sectional area.

Conclusion

Similar increases in strength and power performance were observed in men and women over 8 weeks of velocity-based resistance training. However, some results suggest that strength and power gains favor using 40% rather than 20% velocity loss in women.

Sex and Age-Group Differences in Strength, Jump, Speed, Flexibility, and Endurance Performances of Swedish Elite Gymnasts Competing in TeamGym

Purpose: To analyze sex and age group differences in strength, jump, speed, flexibility, and endurance performances of TeamGym athletes. Methods: A total of 91 Swedish elite gymnasts (junior female, n = 26, age = 15.4 y; senior female, n = 23, age = 20.0 y; junior male, n = 19, age = 15.6 y; senior male, n = 23, age = 20.6 y) participated in three testing sessions on three separate days. These were: (1) a series of flexibility tests for the lower- and upper-body; (2) strength tests for the lower- and upper-body; and (3) various types of jumps, a 20-m sprint-run, and a 3,000-m run test. Results: Males were 24% stronger in the back squat one-repetition maximum (relative to body mass) compared to females (P < 0.001, H g = 1.35). In the pull-ups and dips, 2.4 and 2.3 times more repetitions were completed by the males compared to the females (both P < 0.001, 0.70 ≤ R ≤ 0.77). However, females were similarly strong as males in the hanging sit-ups test (P = 0.724). The males jumped 29, 34, 33, and 17% higher in the squat jump (SJ), countermovement jump (CMJ), countermovement jump with arm swing (CMJa), and drop jump (DJ), respectively, compared to the females (all P ≤ 0.002, 0.14 ≤η p 2   ≤ 0.60). In the 20-m sprint run, males were 4% faster than females (P < 0.001, R = 0.40). Moreover, the females had significantly better flexibility than the males in the trunk forward bending, front split, and side split tests (all P < 0.001, 0.24 ≤η p 2 ≤ 0.54). In the 3,000-m run test, males were 11% faster than females (P < 0.001,η p 2 ≤ 0.54). Compared to junior athletes, seniors performed better in the pull-ups, dips, SJ, CMJ, CMJa, and 20-m sprint-run tests (all P ≤ 0.012, 0.31 ≤ R ≤ 0.56, 0.16 ≤η p 2 ≤ 0.25), with separate within-sex age-group differences (i.e., juniors vs. seniors) that were significant for the males but not for the females in the SJ, CMJ, CMJa, and 20-m sprint-run tests (males: all P < 0.001, 0.67 ≤ R ≤ 0.69, 1.37 ≤ H g ≤ 2.01; females: all P = 0.298-732). Conclusions: Large sex and age-group differences were observed for most physical performance metrics with specific within-sex age-group differences only observed for male athletes, with male seniors performing better than juniors in the SJ, CMJ, CMJa, and 20-m sprint-run tests.

Is the OUTPUT Sports Unit Reliable and Valid When Estimating Back Squat and Bench Press Concentric Velocity?

ABSTRACT

Merrigan, JJ and Martin, JR. Is the OUTPUT sports unit reliable and valid when estimating back squat and bench press concentric velocity? J Strength Cond Res XX(X): 000-000, 2020-This study evaluated the reliability and concurrent validity of the OUTPUT sports inertial unit to measure concentric velocity of free-weight back squat and bench press exercises. Eleven men and women performed back squat and bench press 1 repetition maximum (1RM) testing. One week later, subjects performed 3 repetitions of each exercise with 35, 45, 55, 65, 75, and 85% 1RM (18 total repetitions). The OUTPUT and 4 cable extension transducers (criterion) simultaneously recorded the mean and peak velocity. The OUTPUT had acceptable reliability for all loads except 85% 1RM for back squat and bench press (intraclass correlation coefficient = 0.72-0.96, coefficient of variation = 0.03-0.12). High systematic biases existed for the mean and peak velocity for the back squat and bench press, according to Bland-Altman plot's wide limits of agreement and ordinary least products regressions. According to Bland-Altman plots, OUTPUT tended to overestimate bench press velocity and overestimate back squat velocity at slower velocities. Least products regression analyses determined proportional bias existed for the mean and peak velocity of the back squat and peak velocity of the bench press. In conclusion, researchers and practitioners are advised not to compare velocity estimates of the OUTPUT unit with criterion devices because these methods cannot be used interchangeably. However, because of the demonstrated reliability when estimating the mean and peak velocity, strength and conditioning practitioners may find the OUTPUT unit valuable for monitoring performance of the back squat and bench press exercises. Yet, caution should be taken when evaluating loads ≥85% 1RM.

Delayed potentiation effects on neuromuscular performance after optimal load and high load resistance priming sessions using velocity loss

Aim: (i) to compare the effects of two different low-volume resistance priming sessions, where the external load is modified on neuromuscular performance after 6 h of rest; and (ii) to identify the effects on psychological readiness in participants with resistance training experience. Methods: Eleven participants (Body mass: 77.0 ± 8.9 kg; Body height: 1.76 ± 0.08 m; Half squat repetition maximum: 139.8 ± 22.4 kg) performed the priming session under three experimental conditions in a randomized and cross-over design during the morning. The control (CON) condition: no resistance training, "optimal load" (OL) condition: two half-squat sets with a velocity loss of around 20% were performed with the "optimal load", and 80% of repetition maximum (80% RM) condition: 2 half-squat sets with a velocity loss of around 20% were performed with the 80% RM. Countermovement jump (CMJ), mean power with OL (MP_OL) and 80% RM (MP_80RM), and mean velocity with OL (MV_OL) and 80% RM (MV_80RM) were assessed six hours after the intervention. Subjective readiness was also recorded prior to resistance training and evaluation. Significance was set at p < 0.05. Results: CMJ was higher after the 80% RM intervention than CON (p < 0.001; Δ = 6.5% [3.4-9.5]). MP_OL and MV_OL seemed to be unaffected by both morning sessions. Higher MP_80RM (p = 0.044; Δ = 9.7% [4.0-15.6]; d = 0.24[0.10-0.37]) and MV_80RM (p = 0.004; Δ = 8.1% [3.2-13.3]; d = 0.32[0.13-0.52]) after 80% RM than after CON were observed. No effect was observed on psychological readiness. Conclusions: 80% RM priming session increased CMJ height and the capacity to generate power and velocity under a high-load condition without any effect on psychological readiness.

Effectiveness of Accentuated Eccentric Loading: Contingent on Concentric Load

PURPOSE

To identify acute effects of a single accentuated eccentric loading (AEL) repetition on subsequent back-squat kinetics and kinematics with different concentric loads.

METHODS

Resistance-trained men (N = 21) participated in a counterbalanced crossover design and completed 4 protocols (sets × repetitions at eccentric/concentric) as follows: AEL65, 3 × 5 at 120%/65% 1-repetition maximum (1-RM); AEL80, 3 × 3 at 120%/80% 1-RM; TRA65, 3 × 5 at 65%/65% 1-RM; and TRA80, 3 × 3 at 80%/80% 1-RM. During AEL, weight releasers disengaged from the barbell after the eccentric phase of the first repetition and remained off for the remaining repetitions. All repetitions were performed on a force plate with linear position transducers attached to the barbell, from which eccentric and concentric peak and mean velocity, force, and power were derived.

RESULTS

Eccentric peak velocity (-0.076 [0.124] m·s-1; P = .01), concentric peak force (187.8 [284.4] N; P = .01), eccentric mean power (-145.2 [62.0] W; P = .03), and eccentric peak power (-328.6 [93.7] W; P < .01) during AEL65 were significantly greater than TRA65. When collapsed across repetitions, AEL65 resulted in slower eccentric velocity and power during repetition 1 but faster eccentric and concentric velocity and power in subsequent repetitions (P ≤ .04). When comparing AEL80 with TRA80, concentric peak force (133.8 [56.9] N; P = .03), eccentric mean power (-83.57 [38.0] W; P = .04), and eccentric peak power (-242.84 [67.3] W; P < .01) were enhanced.

CONCLUSIONS

Including a single supramaximal eccentric phase of 120% 1-RM increased subsequent velocity and power with concentric loads of 65% 1-RM, but not 80% 1-RM. Therefore, AEL is sensitive to the magnitude of concentric loads, which requires a large relative difference to the eccentric load, and weight releasers may not need to be reloaded to induce performance enhancement.

Isometric Mid-thigh Pull Kinetics: Sex Differences and Response to Whole-Body Vibration

Merrigan, JJ, Dabbs, NC, and Jones, MT. Isometric mid-thigh pull kinetics: Sex differences and response to whole-body vibration. J Strength Cond Res 34(9): 2407-2411, 2020-The purpose was to investigate whether whole-body vibration's (WBV's) effect on force-time characteristics is dependent on time and sex. Subjects (men, n = 18; women, n = 18) performed a static quarter squat with WBV (frequency: 30 Hz; amplitude: 2-4 mm) and without for 5 × 30 seconds repetitions (1:1, WBV:rest). Next, they performed 2 sets of 3 repetitions of the isometric mid-thigh pull (IMTP) with 3 minutes of intraset rest and 5 minutes of interset rest. Peak force (PF) and rate of force development (RFD) from 0 to 50, 0 to 150, and 0 to 250 milliseconds (RFD50, RFD150, and RFD250) were analyzed (p < 0.05). A significant effect of condition existed for PF (p = 0.019) and RFD from 0 to 250 seconds (p = 0.031). In women, RFD was moderately affected immediately post-WBV (p = 0.070; d = 0.49). Yet in men, the effect of WBV on RFD existed 15 minutes after exposure (p = 0.017; d = 0.36). In absolute terms men produced more PF than women (1,008.6 ± 289.7 N; p < 0.001). All RFD bands were greater in men than those of women (RFD50, 5,519.3 ± 2,927.2 N·s; RFD150, 3,361.4 ± 1,385.3 N·s; RFD250, 2,505.7 ± 867.1 N·s; p < 0.05). However, relative to fat-free mass, PF in men (40.1 ± 7.2 N·kg) was not different from women (37.7 ± 6.4 N·kg; p = 0.284). The same was true for RFD150 (21.1 ± 24.1 N·kg·s; p = 0.084) and RFD250 (10.9 ± 14.1 N·kg·s; p = 0.128). Yet, RFD50 remained greater in men (139.1 ± 33.6 N·kg·s) than that of women (86.8 ± 34.5 N·kg·s; p = 0.034). Current WBV protocols resulted in trivial to moderate effects on IMTP forces, which may be dependent on sex and time. Finally, it is recommended that women complete movements with the intent to move weight quickly to improve early RFD.

Retrospective Cohort Analysis of the Army Physical Fitness Test and the Occupational Physical Assessment Test in Reserve Officer Training Corps Cadets: A Brief Report

INTRODUCTION

Because of the physical fitness requirements of Military Occupational Specialties (MOSs) within the US Army, fitness testing batteries have been developed. The Occupational Physical Assessment Test (OPAT) has been used for determining occupation assignment and is meant to assess upper and lower body muscular power, muscular strength, and aerobic capacity. The Army Physical Fitness Test (APFT) is a general fitness assessment meant to test upper and lower body muscular endurance and aerobic capacity. Comparisons of the two testing batteries as well as evaluation of potential sex differences are missing from current literature. Therefore, the purpose of this study was to investigate the sex differences in APFT and OPAT performances, as well as the relationship between the APFT and OPAT individual test events.

MATERIALS AND METHODS

A retrospective analysis, approved by the university's institutional review board, was conducted on a sample of 90 Reserve Officer Training Corps (ROTC) cadets (men, n = 72, age = 19.7 ± 2.2 years, height = 1.79 ± 0.21 m, mass = 75.18 ± 12.38 kg; women, n = 18, age = 19.8 ± 2.2 years, height = 1.63 ± 0.09 m, mass = 65.56 ± 9.03 kg) from the Fall 2018 semester. The cadets completed the APFT (maximal push-ups, maximal sit-ups, 2-mile run) and OPAT (standing long jump, seated power throw, a deadlift test, and interval aerobic run) protocols per army standards. Analysis of variance assessed sex differences and correlation coefficients were computed to examine the strength of relationships between individual test events (p < 0.05).

RESULTS

All APFT and OPAT event performances were lower in women compared to men (p < 0.05), except the sit-up test (p = 0.382). Seated power throw (Z = 2.285; p = 0.011), 2-mile run (Z = 1.97; p = 0.024), and strength deadlift (Z = 1.783; p = 0.037) were more highly correlated to push-up than aerobic interval run. The standing long jump (Z = 1.741; p = 0.041), power throw (Z = 3.168; p = 0.001), strength deadlift (Z = 2.989; p = 0.001), and shuttle run (Z = 2.933 p = 0.002) were less correlated with the sit-up than 2-mile run. The interval aerobic run was more related to the 2-mile run than the power throw (Z = 1.809, p = 0.035). Compared to the aerobic interval run, the standing long jump (Z = 2.969, p = 0.001) and strength deadlift (Z = 4.237, p < 0.001) were more related to the seated power throw.

CONCLUSIONS

Sex differences and varied relationships among individual events on two common military fitness test batteries were observed. Lower performances on APFT and OPAT by women may suggest the need to evaluate potential training methods to assist women in reaching their desired MOS. Further, individual OPAT events displayed weaker relationships compared with the relationships among individual APFT event, suggesting a greater degree of redundancy among the events on the APFT. Therefore, the combination of APFT and OPAT may offer a greater opportunity to measure physical fitness capabilities as related to various military job performance tasks.

Does Sex Impact the Differences and Relationships in the One Repetition Maximum Performance Across Weightlifting Overhead Pressing Exercises?

Soriano, MA, García-Ramos, A, Calderbank, J, Marín, PJ, Sainz de Baranda, P, and Comfort, P. Does sex impact the differences and relationships in the one repetition maximum performance across weightlifting overhead pressing exercises? J Strength Cond XX(X): 000-000, 2020-This study aimed to determine the impact of sex on the differences and relationships of the one repetition maximum (1RM) performance between 3 overhead pressing exercises (push press [PP], push jerk [PJ] and split jerk [SJ]). 15 men (body mass [BM]: 82.3 ± 9.9 kg; weightlifting training experience: 2.6 ± 1.6 years) and 15 women (BM: 64.4 ± 7.0 kg; weightlifting training experience: 2.2 ± 1.4 years) participated in this study. A ratio-scaled (1RM·BM) was used for the comparison between them. The 1RM of the 3 exercises were evaluated within the same testing session using a combined 1RM assessment method. The interaction effect of exercise and sex did not reach statistical significance (p = 0.671; η = 0.001). In contrast, there were significant main effects of exercise (p ≤ 0.01) and sex (p < 0.001) with medium (η = 0.096) and large effect sizes (η = 0.306), respectively. A similar main effect of exercise was reported for both men (PP [1.0 ± 0.1 kg·kg] < PJ [1.1 ± 0.2 kg·kg] ∼ SJ [1.2 ± 0.2 kg·kg]) and women (PP [0.8 ± 0.1 kg·kg] < PJ [0.9 ± 0.2 kg·kg] ∼ SJ [0.9 ± 0.2 kg·kg]). The 1RM performance of the 3 exercises was significantly correlated for men (r [range] = 0.856-0.963) and women (r [range] = 0.636-0.925). Sex does not affect the differences in the 1RM performance across weightlifting overhead pressing exercises. However, stronger correlations and lower variation in the 1RM performance during the PP, PJ, and SJ are expected for men compared with women.