The aim of this study was to examine the kinematics and kinetics (force, velocity, and acceleration) and blood lactate concentration with the VersaPulley (VP) device in comparison with free-weight (FW) exercise at a similar external load. Fifteen rugby players randomly performed 2 training sessions of 6 sets of 6 repetitions with 20 s of recovery between sets of the high-pull exercise with the VP and the FW. The training sessions were separated by 72 h. Barbell displacement (cm), peak velocity (m/s), peak acceleration (m/s2), mean propulsive velocity (m/s), mean propulsive acceleration (m/s2), propulsive phase (%), and mean and maximal force (N) were continuously recorded during each repetition. Blood lactate concentration was measured after each training session (end) and 3 min and 5 min later. Barbell displacement (+4.8%, small ES), peak velocity (+4.5% small ES), mean propulsive acceleration (+8.8%, small ES), and eccentric force (+26.7, large ES) were substantially higher with VP than with FW. Blood lactate concentration was also greater after the VP exercise (end +32.9%, 3 min later +36%, 5 min later +33.8%; large ES). Maximal concentric force was substantially higher with FW than VP during the 6th set (+6.4%, small ES). In the cohort and exercise investigated in the current study, VP training can be considered an efficient training device to induce an accentuated eccentric overload and augmented metabolic demands (ie, blood lactate concentration).
F. Javier Núñez, Luis J. Suarez-Arrones, Paul Cater, and Alberto Mendez-Villanueva
Corrado Lupo, Alexandru Nicolae Ungureanu, Gennaro Boccia, Andrea Licciardi, Alberto Rainoldi, and Paolo Riccardo Brustio
Evaluation Lower- and upper-limb neuromuscular function were evaluated using peak concentric force during the execution of the CMJ and PPU tests. Both tests were quantified through a piezoelectric portable force platform with charge amplifier (Kistler 9286AA, Kistler Instrument Corp, Winterthur, Switzerland
John R. Harry, John Krzyszkowski, Luke D. Chowning, and Kristof Kipp
–posterior yank, average vertical force during eccentric yielding, and average anterior–posterior concentric force were all important predictors of jump distance (MSE: 0.006; R 2 : .998; adjusted R 2 : .991; P < .001). Pearson product–moment correlation coefficients identified jump height ( P = .029) and
John J. McMahon, Paul A. Jones, Timothy J. Suchomel, Jason Lake, and Paul Comfort
-performance measures (peak and mean concentric force, power and velocity, and impulse) to validate previous findings. 4 , 7 We hypothesized that a high RSImod would be associated with larger force, power, and velocity but similar or smaller countermovement displacements, both in terms of the peak values attained and
Hermann Zbinden-Foncea, Isabel Rada, Jesus Gomez, Marco Kokaly, Trent Stellingwerff, Louise Deldicque, and Luis Peñailillo
Purpose: To examine the effects of a moderate dose of caffeine in elite male volleyball players on countermovement-jump (CMJ) performance, as well as temporal concentric- and eccentric-phase effects. Methods: Ten elite male volleyball players took part in 2 experimental days via a randomized crossover trial 1 wk apart in which they ingested either 5 mg/kg of caffeine or a placebo in double-blind fashion. Heart rate and blood pressure were measured at rest and 60 min postingestion. Afterward, subjects also performed 3 CMJ trials 60 min postingestion, of which the average was used for further analysis. They filled out a questionnaire on possible side effects 24 h posttrial. Results: Caffeine intake, compared with placebo, increased CMJ peak concentric force (6.5% ± 6.4%; P = .01), peak power (16.2% ± 8.3%; P < .01), flight time (5.3% ± 3.4%; P < .01), velocity at peak power (10.6% ± 8.0%; P < .01), peak displacement (10.8% ± 6.5%; P < .01), peak velocity (12.6% ± 7.4%; P < .01), peak acceleration (13.5% ± 8.5%; P < .01), and the force developed at peak power (6.0% ± 4.0%; P < .01) and reduced the time between peak power and peak force (16.7% ± 21.6%, P = .04). Caffeine increased diastolic blood pressure by 13.0% ± 8.9% (P < .05), whereas no adverse side effects were found. Conclusions: The ingestion of 5 mg/kg of anhydrous caffeine improves overall CMJ performance without inducing side effects.
Matthew T.G. Pain
Bilateral deficit is well documented; however, bilateral deficit is not present in all tasks and is more likely in dynamic activities than isometric activities. No definitive mechanism(s) for bilateral deficit is known but an oft cited mechanism is lower activation of fast twitch motor units. The aim of this study was to produce comparable and consistent one and two legged drop jumps to examine bilateral deficit in elite power athletes and elite endurance athletes. Seven power athletes and seven endurance athletes performed single and double leg drop jumps from a range of heights that equalized loading per leg in terms of: height dropped, energy absorbed, and momentum absorbed. Force and motion data were collected at 800 Hz. Bilateral deficit for jump height, peak concentric force, and peak concentric power were calculated. Power athletes had a significantly greater (P < .05) bilateral deficit for jump height and peak power, possibly due to power athletes having more fast twitch motor units, however, endurance athletes generally had a bilateral surfeit which could confound this inference. Results indicate that equalizing loading by impulse per leg is the most appropriate and that a consistent drop height can be obtained with a short 10 minute coaching session.
Zachary Legault, Nicholas Bagnall, and Derek S. Kimmerly
The study aimed to examine the effects that L-glutamine supplementation has on quadriceps muscle strength and soreness ratings following eccentric exercise. It was hypothesized that glutamine ingestion would quicken the recovery rate of peak force production and decrease muscle soreness ratings over a 72-hr recovery period. Sixteen healthy participants (8♀/8♂; 22 ± 4 years) volunteered in a double-blind, randomized, placebo-controlled crossover study. Supplement conditions consisted of isoenergetic placebo (maltodextrin, 0.6 g·kg-1·day-1) and L-glutamine (0.3 g·kg-1·day-1 + 0.3 g·kg-1·day-1 maltodextrin) ingestion once per day over 72 hr. Knee extensor peak torque at 0°, 30°, and 180° per second and muscle soreness were measured before, immediately following, 24, 48, and 72 hr posteccentric exercise. Eccentric exercise consisted of 8 sets (10 repetitions/set) of unilateral knee extension at 125% maximum concentric force with 2-min rest intervals. L-glutamine resulted in greater relative peak torque at 180°/sec both immediately after (71 ± 8% vs. 66 ± 9%), and 72 hr (91 ± 8% vs. 86 ± 7%) postexercise (all, p < .01). In men, L-glutamine produced greater (p < .01) peak torques at 30°/sec postexercise. Men also produced greater normalized peak torques at 30°/sec (Nm/kg) in the L-glutamine condition than women (all, p < .05). In the entire sample, L-glutamine resulted in lower soreness ratings at 24 (2.8 ± 1.2 vs. 3.4 ± 1.2), 48 (2.6 ± 1.4 vs. 3.9 ± 1.2), and 72 (1.7 ± 1.2 vs. 2.9 ± 1.3) hr postexercise (p < .01). The L-glutamine supplementation resulted in faster recovery of peak torque and diminished muscle soreness following eccentric exercise. The effect of L-glutamine on muscle force recovery may be greater in men than women.
Qian Zhang, Liang Zhang, Bing Yan, and Olivier Girard
-off velocity, maximal concentric force, and rate of force development ( P ≥ .059; .05 ≤ η p 2 ≤ .14 ; Table 1 ). Table 1 Neuromechanical Parameters Across the Different Eccentric Loading Reduction Conditions for the WJS WJS 0% WJS 25% WJS 50% WJS 75% WJS 100% ANOVA P ( η p 2 ) Eccentric time, s 0.45 (0
Samuel Ryan, Emidio Pacecca, Jye Tebble, Joel Hocking, Thomas Kempton, and Aaron J. Coutts
Strength Tests Monitoring measure Mean SD Subjects CV (90% CI) SNR SNR rating Heart rate, n = 176 HRex, bpm 81.6 6.2 41 7.4 (6.5–8.9) 5.3 Good HRR, bpm 35.4 10.6 41 23.9 (16.2–28.6) 1.4 Acceptable CMJs, n = 206 Jump height, cm 38.0 4.4 35 5.9 (5.4–6.6) 1.5 Acceptable Mean concentric force, N 1806.4 225
Zachary M. Gillen, Lacey E. Jahn, Marni E. Shoemaker, Brianna D. McKay, Alegra I. Mendez, Nicholas A. Bohannon, and Joel T. Cramer
), and h is drop height (in meters). The point at which the force signal crossed p downward , after the initial peak eccentric impact force and after the trough in force representing the transition from eccentric to concentric force, was considered the start of the concentric phase ((b) above, Figure