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We, the Authors, Editors, and Publishers of the International Journal of Sports Physiology and Performance ( IJSPP ), have retracted the following article in whole: Dos’Santos T, Jones PA, Kelly J, McMahon JJ, Comfort P, Thomas C Effect of sampling frequency on isometric midthigh-pull kinetics

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Tai T. Tran, Lina Lundgren, Josh Secomb, Oliver R.L. Farley, G. Gregory Haff, Laurent B. Seitz, Robert U. Newton, Sophia Nimphius and Jeremy M. Sheppard

Purpose:

To determine whether a previously validated performance-testing protocol for competitive surfers is able to differentiate between Australian elite junior surfers selected (S) to the national team and those not selected (NS).

Methods:

Thirty-two elite male competitive junior surfers were divided into 2 groups (S = 16, NS = 16). Their age, height, body mass, sum of 7 skinfolds, and lean-body-mass ratio (mean ± SD) were 16.17 ± 1.26 y, 173.40 ± 5.30 cm, 62.35 ± 7.40 kg, 41.74 ± 10.82 mm, 1.54 ± 0.35 for the S athletes and 16.13 ± 1.02 y, 170.56 ± 6.6 cm, 61.46 ± 10.10 kg, 49.25 ± 13.04 mm, 1.31 ± 0.30 for the NS athletes. Power (countermovement jump [CMJ]), strength (isometric midthigh pull), 15-m sprint paddling, and 400-m endurance paddling were measured.

Results:

There were significant (P ≤ .05) differences between the S and NS athletes for relative vertical-jump peak force (P = .01, d = 0.9); CMJ height (P = .01, d = 0.9); time to 5-, 10-, and 15-m sprint paddle; sprint paddle peak velocity (P = .03, d = 0.8; PV); time to 400 m (P = .04, d = 0.7); and endurance paddling velocity (P = .05, d = 0.7).

Conclusions:

All performance variables, particularly CMJ height; time to 5-, 10-, and 15-m sprint paddle; sprint paddle PV; time to 400 m; and endurance paddling velocity, can effectively discriminate between S and NS competitive surfers, and this may be important for athlete profiling and training-program design.

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Lachlan P. James, Emma M. Beckman, Vincent G. Kelly and G. Gregory Haff

Purpose:

To determine whether the maximal strength, impulse, and power characteristics of competitive mixed-martial-arts (MMA) athletes differ according to competition level.

Methods:

Twenty-nine male semiprofessional and amateur MMA competitors were stratified into either higher-level (HL) or lower-level (LL) performers on the basis of competition grade and success. The 1-repetition-maximum (1RM) squat was used to assess lower-body dynamic strength, and a spectrum of impulse, power, force, and velocity variables were evaluated during an incremental-load jump squat. In addition, participants performed an isometric midthigh pull (IMTP) and 1RM bench press to determine whole-body isometric force and upper-body dynamic strength capabilities, respectively. All force and power variables were expressed relative to body mass (BM).

Results:

The HL competitors produced significantly superior values across a multitude of measures. These included 1RM squat strength (1.84 ± 0.23 vs 1.56 ± 0.24 kg BM; P = .003), in addition to performance in the incremental-load jump squat that revealed greater peak power (P = .005–.002), force (P = .002–.004), and velocity (P = .002–.03) at each load. Higher measures of impulse (P = .01–.04) were noted in a number of conditions. Average power (P = .002–.02) and velocity (P = .01–.04) at all loads in addition to a series of rate-dependent measures were also superior in the HL group (P = .005–.02). The HL competitors’ 1RM bench-press values approached significantly greater levels (P = .056) than the LL group’s, but IMTP performance did not differ between groups.

Conclusions:

Maximal lower-body neuromuscular capabilities are key attributes distinguishing HL from LL MMA competitors. This information can be used to inform evidenced-based training and performance-monitoring practices.

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Josh L. Secomb, Sophia Nimphius, Oliver R.L. Farley, Lina Lundgren, Tai T. Tran and Jeremy M. Sheppard

Purpose:

To identify whether there are any significant differences in the lower-body muscle structure and countermovement-jump (CMJ) and squat-jump (SJ) performance between stronger and weaker surfing athletes.

Methods:

Twenty elite male surfers had their lower-body muscle structure assessed with ultrasonography and completed a series of lower-body strength and jump tests including isometric midthigh pull (IMTP), CMJ, and SJ. Athletes were separated into stronger (n = 10) and weaker (n = 10) groups based on IMTP performance.

Results:

Large significant differences were identified between the groups for vastus lateralis (VL) thickness (P = .02, ES = 1.22) and lateral gastrocnemius (LG) pennation angle (P = .01, ES = 1.20), and a large nonsignificant difference was identified in LG thickness (P = .08, ES = 0.89). Furthermore, significant differences were present between the groups for peak force, relative peak force, and jump height in the CMJ and SJ (P < .01−.05, ES = 0.90−1.47) and eccentric peak velocity, as well as vertical displacement of the center of mass during the CMJ (P < .01, ES = 1.40−1.41).

Conclusion:

Stronger surfing athletes in this study had greater VL and LG thickness and LG pennation angle. These muscle structures may explain their better performance in the CMJ and SJ. A unique finding in this study was that the stronger group appeared to better use their strength and muscle structure for braking as they had significantly higher eccentric peak velocity and vertical displacement during the CMJ. This enhanced eccentric phase may have resulted in a greater production and subsequent utilization of stored elastic strain energy that led to the significantly better CMJ performance in the stronger group.

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Kris Beattie, Brian P. Carson, Mark Lyons and Ian C. Kenny

Cycling economy (CE), power output at maximal oxygen uptake (WV̇O2max), and anaerobic function (ie, sprinting ability) are considered the best physiological performance indicators in elite road cyclists. In addition to cardiovascular function, these physiological indicators are partly dictated by neuromuscular factors. One technique to improve neuromuscular function in athletes is through strength training. The aim of this study was to investigate the effect of a 20-wk maximal- and explosive-strength-training intervention on strength (maximal strength, explosive strength, and bike-specific explosive strength), WV̇O2max, CE, and body composition (body mass, fat and lean mass) in cyclists. Fifteen competitive road cyclists were divided into an intervention group (endurance training and strength training: n = 6; age, 38.0 ± 10.2 y; weight, 69.1 ± 3.6 kg; height, 1.77 ± 0.04 m) and a control group (endurance training only: n = 9; age, 34.8 ± 8.5 y; weight, 72.5 ± 7.2 kg; height, 1.78 ± 0.05 m). The intervention group strength-trained for 20 wk. Each participant completed 3 assessments: physiology (CE, WV̇O2max, power at 2 and 4 mmol/L blood lactate), strength (isometric midthigh pull, squat-jump height, and 6-s bike-sprint peak power), and body composition (body mass, fat mass, overall leanness, and leg leanness). The results showed significant between- and within-group changes in the intervention group for maximal strength, bike-specific explosive strength, absolute WV̇O2max, body mass, overall leanness, and leg leanness at wk 20 (P < .05). The control group showed no significant within-group changes in measures of strength, physiology, or body composition. This study demonstrates that 20 wk of strength training can significantly improve maximal strength, bike-specific explosive strength, and absolute WV̇O2max in competitive road cyclists.

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Eric R. Helms, Caryn Zinn, David S. Rowlands, Ruth Naidoo and John Cronin

Purpose:

Athletes risk performance and muscle loss when dieting. Strategies to prevent losses are unclear. This study examined the effects of two diets on anthropometrics, strength, and stress in athletes.

Methods:

This double-blind crossover pilot study began with 14 resistance-trained males (20-43 yr) and incurred one dropout. Participants followed carbohydrate-matched, high-protein low-fat (HPLF) or moderate-protein moderate-fat (MPMF) diets of 60% habitual calories for 2 weeks. Protein intakes were 2.8g/kg and 1.6g/kg and mean fat intakes were 15.4% and 36.5% of calories, respectively. Isometric midthigh pull (IMTP) and anthropometrics were measured at baseline and completion. The Daily Analysis of Life Demands of Athletes (DALdA) and Profile of Mood States (POMS) were completed daily. Outcomes were presented statistically as probability of clinical benefit, triviality, or harm with effect sizes (ES) and qualitative assessments.

Results:

Differences of effect between diets on IMTP and anthropometrics were likely or almost certainly trivial, respectively. Worse than normal scores on DALDA part A, part B and the part A “diet” item were likely more harmful (ES 0.32, 0.4 and 0.65, respectively) during MPMF than HPLF. The POMS fatigue score was likely more harmful (ES 0.37) and the POMS total mood disturbance score (TMDS) was possibly more harmful (ES 0.29) during MPMF than HPLF.

Conclusions:

For the 2 weeks observed, strength and anthropometric differences were minimal while stress, fatigue, and diet-dissatisfaction were higher during MPMF. A HPLF diet during short-term weight loss may be more effective at mitigating mood disturbance, fatigue, diet dissatisfaction, and stress than a MPMF diet.

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Danielle T. Gescheit, Stuart J. Cormack, Machar Reid and Rob Duffield

Purpose:

To determine how consecutive days of prolonged tennis match play affect performance, physiological, and perceptual responses.

Methods:

Seven well-trained male tennis players completed 4-h tennis matches on 4 consecutive days. Pre- and postmatch measures involved tennis-specific (serve speed and accuracy), physical (20-m sprint, countermovement jump [CMJ], shoulder-rotation maximal voluntary contraction, isometric midthigh pull), perceptual (Training Distress Scale, soreness), and physiological (creatine kinase [CK]) responses. Activity profile was assessed by heart rate, 3D load (accumulated accelerations measured by triaxial accelerometers), and rating of perceived exertion (RPE). Statistical analysis compared within- and between-days values. Changes (± 90% confidence interval [CI]) ≥75% likely to exceed the smallest important effect size (0.2) were considered practically important.

Results:

3D load reduced on days 2 to 4 (mean effect size ± 90% CI –1.46 ± 0.40) and effective playing time reduced on days 3 to 4 (–0.37 ± 0.51) compared with day 1. RPE did not differ and total points played only declined on day 3 (–0.38 ± 1.02). Postmatch 20-m sprint (0.79 ± 0.77) and prematch CMJ (–0.43 ± 0.27) performance declined on days 2 to 4 compared with prematch day 1. Although serve velocity was maintained, compromised postmatch serve accuracy was evident compared with prematch day 1 (0.52 ± 0.58). CK increased each day, as did ratings of muscle soreness and fatigue.

Conclusions:

Players reduced external physical loads, through declines in movement, over 4 consecutive days of prolonged competitive tennis. This may be affected by tactical changes and pacing strategies. Alongside this, impairments in sprinting and jumping ability, perceptual and biochemical markers of muscle damage, and reduced mood states may be a function of neuromuscular and perceptual fatigue.

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Antonio Dello Iacono, Stephanie Valentin, Mark Sanderson and Israel Halperin

Sport scientists and applied practitioners regularly monitor and prescribe training programs based on assessments of force production tests. Two examples of such tests are the isometric midthigh pull (IMTP) and the isometric squat tests. 1 , 2 Both require subjects to stand on a force plate and

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Reid Reale, Gary Slater, Gregory R. Cox, Ian C. Dunican and Louise M. Burke

; CON = control group. Figure 2 —Laboratory data collection and physical testing undertaken on Days −1 and 0 (preintervention) and Day 6 (postintervention). USG = urine specific gravity; Na = sodium; K = potassium; Cl = chloride; U = urea; Cr = creatinine; IMTP = isometric midthigh pull; IBP = isometric

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Matthew A. Wyon, Roger Wolman, Nicolas Kolokythas, Karen Sheriff, Shaun Galloway and Adam Mattiussi

, which did not contain anticoagulants by a trained phlebotomist before being sent off for analysis to an independent laboratory. Muscle Function Tests Participants underwent familiarization practices prior to the isometric midthigh pulls (IMTP) tests as they were already familiar with the muscular power