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Dennis van Erck, Eric J. Wenker, Koen Levels, Carl Foster, Jos J. de Koning and Dionne A. Noordhof

the maximal oxygen uptake [ V ˙ O 2 max] and V ˙ O 2 at the lactate threshold), performance O 2 deficit, and gross mechanical efficiency (GE). GE, defined as the percentage of metabolic power input, that is, converted into mechanical power output (PO), is considered the most valid definition of

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Liam P. Kilduff, Huw Bevan, Nick Owen, Mike I.C. Kingsley, Paul Bunce, Mark Bennett and Dan Cunningham

Purpose:

The ability to develop high levels of muscle power is considered an essential component of success in many sporting activities; however, the optimal load for the development of peak power during training remains controversial. The aim of the present study was to determine the optimal load required to observe peak power output (PPO) during the hang power clean in professional rugby players.

Methods:

Twelve professional rugby players performed hang power cleans on a portable force platform at loads of 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their predetermined 1-repetition maximum (1-RM) in a randomized and balanced order.

Results:

Relative load had a significant effect on power output, with peak values being obtained at 80% of the subjects’ 1-RM (4466 ± 477 W; P < .001). There was no significant difference, however, between the power outputs at 50%, 60%, 70%, or 90% 1-RM compared with 80% 1-RM. Peak force was produced at 90% 1-RM with relative load having a significant effect on this variable; however, relative load had no effect on peak rate of force development or velocity during the hang power clean.

Conclusions:

The authors conclude that relative load has a significant effect on PPO during the hang power clean: Although PPO was obtained at 80% 1-RM, there was no significant difference between the loads ranging from 40% to 90% 1-RM. Individual determination of the optimal load for PPO is necessary in order to enhance individual training effects.

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Erin E. Sutton, M. Regina Coll and Patricia A. Deuster

Acute tyrosine ingestion is thought to improve aerobic endurance, muscle strength and endurance, and anaerobic power of men undergoing severe physiologic stress. In a double-blind, crossover study, 20 men (32 ± 1 y old) underwent 2 loadcarriage treadmill sessions, 1 after taking tyrosine (150 mg/kg L-crystalline tyrosine) and 1 after taking placebo. Tyrosine dosage was based on subject weight and ingested 30 min before load carriage. A physical performance battery was administered after the load carriage: maximal and submaximal handgrip, pull-ups, and stair stepping with weight. Total time on treadmill was not significantly lengthened with ingestion of tyrosine (118.9 ± 1.4 min) as compared with placebo (119.2 ± 1.2 min). Total power for stair stepping (tyrosine 223 ± 8 watts, placebo 216 ± 9 watts) and muscle strength and endurance (handgrip) was not significantly improved by tyrosine ingestion. The results indicate that acute ingestion of tyrosine by healthy men has no measurable effect on endurance, muscle strength, or anaerobic power.

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Christos K. Argus, Nicholas D. Gill, Justin W.L. Keogh, Michael R. McGuigan and Will G. Hopkins

Purpose:

There is little literature comparing contrast training programs typically performed by team-sport athletes within a competitive phase. We compared the effects of two contrast training programs on a range of measures in high-level rugby union players during the competition season.

Methods:

The programs consisted of a higher volume-load (strength-power) or lower volume-load (speed-power) resistance training; each included a tapering of loading (higher force early in the week, higher velocity later in the week) and was performed twice a week for 4 wk. Eighteen players were assessed for peak power during a bodyweight countermovement jump (BWCMJ), bodyweight squat jump (BWSJ), 50 kg countermovement jump (50CMJ), 50 kg squat jump (50SJ), broad jump (BJ), and reactive strength index (RSI; jump height divided by contact time during a depth jump). Players were then randomized to either training group and were reassessed following the intervention. Inferences were based on uncertainty in outcomes relative to thresholds for standardized changes.

Results:

There were small between-group differences in favor of strength-power training for mean changes in the 50CMJ (8%; 90% confidence limits, ±8%), 50SJ (8%; ±10%), and BJ (2%; ±3%). Differences between groups for BWCMJ, BWSJ, and reactive strength index were unclear. For most measures there were smaller individual differences in changes with strength-power training.

Conclusion:

Our findings suggest that high-level rugby union athletes should be exposed to higher volume-load contrast training which includes one heavy lifting session each week for larger and more uniform adaptation to occur in explosive power throughout a competitive phase of the season.

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Jeffrey M. McBride, Tyler J. Kirby, Tracie L. Haines and Jared Skinner

Purpose:

The purpose of the current investigation was to determine the relationship between relative net vertical impulse (net vertical impulse (VI)) and jump height in the jump squat (JS) going to different squat depths and utilizing various loads.

Methods:

Ten males with two years of jumping experience participated in this investigation (Age: 21.8 ± 1.9 y; Height: 176.9 ± 5.2 cm; Body Mass: 79.0 ± 7.1 kg, 1RM: 131.8 ± 29.5 kg, 1RM/BM: 1.66 ± 0.27). Subjects performed a series of static jumps (SJS) and countermovement jumps (CMJJS) with various loads (Body Mass, 20% of 1RM, 40% of 1RM) in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth. During the concentric phase of each JS, peak force (PF), peak power (PP), jump height (JH) and relative VI were recorded and analyzed.

Results:

Increasing squat depth corresponded to a decrease in PF and an increase in JH, relative VI for both SJS and CMJJS during all loads. Across all squat depths and loading conditions relative VI was statistically significantly correlated to JH in the SJS (r = .8956, P < .0001, power = 1.000) and CMJJS (r = .6007, P < .0001, power = 1.000). Across all squat depths and loading conditions PF was statistically nonsignificantly correlated to JH in the SJS (r = –0.1010, P = .2095, power = 0.2401) and CMJJS (r = –0.0594, P = .4527, power = 0.1131). Across all squat depths and loading conditions peak power (PP) was significantly correlated with JH during both the SJS (r = .6605, P < .0001, power = 1.000) and the CMJJS (r = .6631, P < .0001, power = 1.000). PP was statistically significantly higher at BM in comparison with 20% of 1RM and 40% of 1RM in the SJS and CMJJS across all squat depths.

Conclusions:

Results indicate that relative VI and PP can be used to predict JS performance, regardless of squat depth and loading condition. However, relative VI may be the best predictor of JS performance with PF being the worst predictor of JS performance.

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Nicola Giovanelli, Filippo Vaccari, Mirco Floreani, Enrico Rejc, Jasmine Copetti, Marco Garra, Lea Biasutti and Stefano Lazzer

massagers. SMFR can promote short-term flexibility improvement, and it does not seem to have negative effects on performance. 2 , 3 , 9 – 11 In fact, no differences in maximal force and power were detected after an SMFR protocol. 2 , 12 Moreover, SMFR has been shown effective for reducing delayed

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Harsh H. Buddhadev and Philip E. Martin

studies have examined the effects of external power output and cadence on aerobic demand or energy expenditure ( Belli & Hintzy, 2002 ; Bigland-Ritchie & Woods, 1974 ; Chavarren & Calbet, 1999 ; Gaesser & Brooks, 1975 ; Marsh & Martin, 1993 ; Samozino, Horvais, & Hintzy, 2006 ). Influences of power

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Tyler J. Kirby, Jeffrey M. McBride, Tracie L. Haines and Andrea M. Dayne

The purpose of this investigation was to determine the relationship between relative net vertical impulse and jump height in a countermovement jump and static jump performed to varying squat depths. Ten college-aged males with 2 years of jumping experience participated in this investigation (age: 23.3 ± 1.5 years; height: 176.7 ± 4.5 cm; body mass: 84.4 ± 10.1 kg). Subjects performed a series of static jumps and countermovement jumps in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth (static jump depth = 0.38 ± 0.08 m, countermovement jump depth = 0.49 ± 0.06 m). During the concentric phase of each jump, peak force, peak velocity, peak power, jump height, and net vertical impulse were recorded and analyzed. Net vertical impulse was divided by body mass to produce relative net vertical impulse. Increasing squat depth corresponded to a decrease in peak force and an increase in jump height and relative net vertical impulse for both static jump and countermovement jump. Across all depths, relative net vertical impulse was statistically significantly correlated to jump height in the static jump (r = .9337, p < .0001, power = 1.000) and countermovement jump (r = .925, p < .0001, power = 1.000). Across all depths, peak force was negatively correlated to jump height in the static jump (r = –0.3947, p = .0018, power = 0.8831) and countermovement jump (r = –0.4080, p = .0012, power = 0.9050). These results indicate that relative net vertical impulse can be used to assess vertical jump performance, regardless of initial squat depth, and that peak force may not be the best measure to assess vertical jump performance.

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Jonathan. P. Little, Scott C. Forbes, Darren G. Candow, Stephen M. Cornish and Philip D. Chilibeck

Creatine (Cr) supplementation increases muscle mass, strength, and power. Arginine α-ketoglutarate (A-AKG) is a precursor for nitric oxide production and has the potential to improve blood flow and nutrient delivery (i.e., Cr) to muscles. This study compared a commercial dietary supplement of Cr, A-AKG, glutamine, taurine, branchedchain amino acids, and medium-chain triglycerides with Cr alone or placebo on exercise performance and body composition. Thirty-five men (~23 yr) were randomized to Cr + A-AKG (0.1 g · kg−1 · d−1 Cr + 0.075 g · kg−1 · d−1 A-AKG, n = 12), Cr (0.1 g · kg−1 · d−1, n = 11), or placebo (1 g · kg−1 · d−1 sucrose, n = 12) for 10 d. Body composition, muscle endurance (bench press), and peak and average power (Wingate tests) were measured before and after supplementation. Bench-press repetitions over 3 sets increased with Cr + A-AKG (30.9 ==6.6 → 34.9 ± 8.7 reps; p < .01) and Cr (27.6 ± 5.9 → 31.0 ± 7.6 reps; p < .01), with no change for placebo (26.8 ± 5.0 → 27.1 ± 6.3 reps). Peak power significantly increased in Cr + A-AKG (741 ± 112 → 794 ± 92 W; p < .01), with no changes in Cr (722 ± 138 → 730 ± 144 W) and placebo (696 ± 63 → 705 ± 77 W). There were no differences in average power between groups over time. Only the Cr-only group increased total body mass (79.9 ± 13.0→81.1 ± 13.8 kg; p < .01), with no significant changes in lean-tissue or fat mass. These results suggest that Cr alone and in combination with A-AKG improves upper body muscle endurance, and Cr + A-AKG supplementation improves peak power output on repeated Wingate tests.

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Samantha G. Fawkner and Neil Armstrong

The purpose of this study was to examine methods of assessing Critical Power (CP) with children. Eight boys and 9 girls (10.3 – 0.4 yrs) completed 3 cycle tests in one day, each at a different constant power output predicted to induce fatigue in 2 to 15 min. Time to exhaustion was recorded, and order of the tests was randomized, with 3 hours recovery between tests. The children repeated these tests and 2 additional tests with at least 24 hr recovery between each test. CP was determined using least squares linear regression analysis of the power — t−1 relationship, for the single day (CP1), the 5 tests from different days (CP2), and the repeated 3 tests from different days (CP3). The 95% limits of agreement (range of percentage differences) were −15.4 to 13.1% (CP1 v CP2), −16.8 to 13.5% (CP1 v CP3), and −8.4 to 6.7% (CP2 v CP3). CP is a robust measure even when only 3 tests are completed in a single day and may be used to provide a simple and useful parameter of exercise intensity for constant load exercise with children.