Subjects were 234 adolescents (mean age: 16 years) who were categorised by gender, activity level and type of sport played. Subjects jumped from a box 0.3 metres high to land on a force plate. Results showed that there were no significant differences (p>0.05) across gender, activity levels, and type of sport played. Across all subjects, the mean peak vertical GRF was 4.5 bodyweights (SD: 1.7). In regard to gender, mean peak vertical GRFs were 4.6 (SD:1.7) and 4.2 (SD:1.4) for males and females respectively. The mean peak vertical GRF for subjects involved in recreational sport 1–3 times per week was 4.4 bodyweights (SD:1.7), while the mean for those playing competitive sport 4–7 times per week was 4.5 bodyweights (SD: 1.7). The mean peak vertical GRF for subjects participating in sports involving jumping and landing activities was 4.6 bodyweights (SD: 1.8) as compared to 4.4 bodyweights (SD: 1.5) for subjects in sports that did not involve jumping activities.

Read...

Nonimpaired college students (N = 63) were randomly assigned to 1 of 4 feedback groups. Subjects were instructed to perform maximal vertical jumps onto a force plate for 3 testing sessions (baseline, 2-minute post-test, and 1-week post-test). Three feedback groups (augmented, sensory, and control I) were tested during all 3 testing sessions, while a fourth feedback group (control II) was evaluated at only 2 sessions (baseline and 1-week post-test). Subjects in the augmented feedback condition were provided information via video and verbal analysis of how to land softer. Subjects in the sensory feedback condition were asked to use the experience of their baseline jumps to document how they could land softer. Subjects in each of the control groups were not provided any extraneous feedback. Peak vertical ground reaction force data were collected for analysis.

The purpose of this study was to examine the effects of external load on vertical ground reaction force, and linear and angular kinematics, during squats. Eight males aged 22.1±0.8 years performed maximal concentric squats using loads ranging from 7 to 70% of one-repetition maximum on a force plate while linear barbell velocity and the angular kinematics of the hip, knee and ankle were recorded. Maximum, average and angle-specific values were recorded. The ground reaction force ranged from 1.67±0.20 to 3.21±0.29 times body weight and increased significantly as external load increased (P<0.05). Bar linear velocity ranged from 0.54±0.11 to 2.50±0.50 m·s⁻¹ and decreased significantly with increasing external load (P<0.05). Hip, knee and ankle angles at maximum ground reaction force were affected by external load (P<0.05). The force–barbell velocity curves were fitted using linear models with coefficients (r...

Thirty male athletes [height: 183.8 (6.8) cm, and mass: 90.6 (9.3) kg; mean (SD)] each completed six 10-m sprints from a standing start. Sprint times were recorded using a tethered running system and the force-time characteristics of the first ground contact were recorded using a recessed force plate. Three to six days later subjects completed three concentric jump squats, using a traditional and split technique, at a range of external loads from 30–70% of one repetition maximum (1RM)

Average power was maximal at all loads between 30% and 60% of 1RM for both squats. Split squat peak power was also maximal between 30% and 60% of 1RM; however, traditional squat peak power was maximal between 50% and 70% of 1RM. Concentric force development is critical to sprint start performance and accordingly maximal concentric jump power is related to sprint acceleration.

Due to a high incidence of anterior cruciate ligament (ACL) re‐injury in alpine ski racers, this study aims to assess functional asymmetry in the countermovement jump (CMJ), squat jump (SJ), and leg muscle mass in elite ski racers with and without anterior cruciate ligament reconstruction (ACL‐R). Elite alpine skiers with ACL‐R (n = 9; 26.2 ± 11.8 months post‐op) and uninjured skiers (n = 9) participated in neuromuscular screening. Vertical ground reaction force during the CMJ and SJ was assessed using dual force plate methodology to obtain phase‐specific bilateral asymmetry indices (AIs) for kinetic impulse (CMJ and SJ phase‐specific kinetic impulse AI). Dual x‐ray absorptiometry scanning was used to assess asymmetry in lower body muscle mass. Compared with controls, ACL‐R skiers had increased AI in muscle mass (P < 0.001), kinetic impulse AI in the CMJ concentric phase (P < 0.05), and the final...

This investigation compared lower extremity function of a control group and a group of patients who underwent anterior cruciate ligament (ACL) reconstruction using a repeated measures post-test only control group design. The ACL reconstruction group consisted of 18 patients at least 6 months postoperative (mean 58±19 weeks) and the control group consisted of 18 healthy, recreationally active individuals. Both groups performed a step-up-and-over test and a forward lunge on a long force plate. During the step-up-and-over test, the control group produced significantly more force during the initial step than the ACL reconstruction group. Also, when the ACL reconstruction patients led with the involved extremity, they were significantly slower.

During the forward lunge test, the impact index and force impulse measurements were significantly greater for the uninvolved leg than the involved leg in the ACL reconstruction group. The implications are that force generation during...

The purpose of this investigation was to determine the existence of bilateral strength and force-production asymmetry and evaluate possible differences based on sex, as well as strength level. Asymmetry was assessed during weight-distribution (WtD) testing, unloaded and lightly loaded static- (SJ) and countermovement-jump (CMJ) testing, and isometric midthigh-pull (IMTP) strength testing. Subjects included 63 athletes (31 male, 32 female) for WtD, SJ, and CMJ tests, while 129 athletes (64 male, 65 female) participated in IMTP testing. Independent-samples t tests were used to determine possible differences in asymmetry magnitude between males and females, as well as between strong and weak athletes

The results of this investigation indicate that females may be more prone to producing forces asymmetrically than males during WtD and jumping tasks. Similarly, weaker athletes displayed more asymmetry than stronger athletes. This may indicate that absolute strength may play a...

Collegiate athletes were evaluated for this study (n=36). Subjects performed SJ, CMJ, and isometric mid-thigh pulls (IMTP). Jumps were analyzed for jump height (JH) and peak power (PP). IMTP was analyzed for peak force (PF) for left and right sides, and values were calculated to produce a peak force symmetry index (PF-SI) score. Correlational statistics were performed examining the relationship between PF-SI and jump variables

The results indicate that force production asymmetry may be detrimental to bilateral vertical jumping performance. The findings should be considered for further investigation on sport-specific tasks.

Read more at: https://www.jstage.jst.go.jp/article/trainology/2/1/2_1/_article/-char/ja/

Fourteen male collegiate athletes (mean ± SD; age = 21 ± 2.4 years; height =176 ± 9.0 cm; body mass = 72.8 ± 9.4 kg) participated in the study. Maximal strength was assessed via an isometric mid-thigh pull (IMTP). Isometric mid-thigh pull testing involved trials with peak force (IPF), maximum rate of force development (mRFD), impulse at 100 ms (IP 100) and 300 ms (IP 300) determined. Sprint and COD performance was measured using 5- and 20-m sprint performance, and a modified 505 test

Results suggest that IP 300 displayed the strongest relationships with 5- and 20-m sprint performance (r = −0.51 and −0.54, respectively). The results demonstrate maximum force production measures during IMTP correlate to sprint and COD ability in collegiate athletes.

Isometric mid-thigh pull force-time measures are related to athletic performance (acceleration and sprinting), and thus are recommended for use in athlete monitoring and assessment.

Read...

The aim of this study was to determine the relationship between isometric measures of force development and dynamic performance. Thirty-nine professional rugby league players participated in this study. Forty-eight hours after trial familiarization, participants performed a maximal isometric midthigh pull, with ∼120–130° bend at the knee, countermovement jump (CMJ), and a 10-m sprint. Force–time data were processed for peak force (PF), force at 100 milliseconds (F100ms), and peak rate of force development (PRFD)

In conclusion, this study provides evidence that measures of maximal strength and explosiveness from isometric force–time curves are related to jump and sprint acceleration performance in professional rugby league players.

Read more at: https://journals.lww.com/nsca-jscr/Fulltext/2011/11000/Relationships_Between_Force_Time_Characteristics.19.aspx