Purpose: To analyze the differences in the force–velocity (F–v) profile assessed under unconstrained (ie, using free weights) and constrained (ie, on a Smith machine) vertical jumps, as well as to determine the between-day reliability. Methods: A total of 23 trained participants (18  y) performed an incremental load squat jump test (with ∼35%, 45%, 60%, and 70% of the subjects’ body mass) on 2 different days using free weights and a Smith machine. Nine of these participants repeated the tests on 2 other days for an exploratory analysis of between-day reliability. F–v variables (ie, maximum theoretical force [F 0], velocity [v 0], and power, and the imbalance between the actual and the theoretically optimal F–v profile) were computed from jump height. Results: A poor agreement was observed between the F–v variables assessed under constrained and unconstrained conditions (intraclass correlation coefficient [ICC] < .50 for all). The height attained during each single jump performed under both constrained and unconstrained conditions showed an acceptable reliability (coefficient of variation < 10%, ICC > .70). The F–v variables computed under constrained conditions showed an overall good agreement (ICC = .75–.95 for all variables) and no significant differences between days (P > .05), but a high variability for v 0, the imbalance between the actual and the theoretically optimal F–v profile, and maximal theoretical power (coefficient of variation = 17.0%–27.4%). No between-day differences were observed for any F–v variable assessed under unconstrained conditions (P > .05), but all of the variables presented a low between-day reliability (coefficient of variation > 10% and ICC < .70 for all). Conclusions: F–v variables differed meaningfully when obtained from constrained and unconstrained loaded jumps, and most importantly seemed to present a low between-day reliability.
Pedro L. Valenzuela, Guillermo Sánchez-Martínez, Elaia Torrontegi, Javier Vázquez-Carrión, Zigor Montalvo, and G. Gregory Haff
Pedro L. Valenzuela, Guillermo Sánchez-Martínez, Elaia Torrontegi, Javier Vázquez-Carrión, Manuela González, Zigor Montalvo, and Grégoire P. Millet
Purpose: Repeated-sprint training (RS) is commonly conducted in normoxia, but its completion with localized (blood-flow restriction [BFR]) or systemic hypoxia has been proven effective for performance enhancement. Yet, few studies have applied these types of RS sessions in racket sports. The authors aimed to determine the acute responses to these types of training in elite badminton players. Methods: Eight male elite badminton players participated in this randomized crossover study. They performed 3 on-court RS sessions, each consisting of 3 sets of 10 repetitions of 10-s badminton-specific movements in normoxia (RSN), systemic normobaric hypoxia (RSH, FiO2 = 14%), or with BFR (RS-BFR, 40% arterial occlusion pressure). Performance, perceptual (ie, rating of perceived exertion), and physiological (ie, pulse saturation, muscle oxygenation, blood lactate, creatine kinase, heart-rate variability) responses were measured after each set and up to 48 h postsession. Results: RS-BFR induced a greater performance impairment (lower distance and accelerations) and a higher local perceived exertion in the legs than RSN and RSH (P < .05), whereas greater overall fatigue was reported with RSH (P < .05). RSH induced a lower saturation (P < .001), but no differences were observed in muscle oxygenation between conditions. No differences in creatine kinase or heart-rate variability were observed at any time point (from baseline up to 48 h after the session). Conclusions: RS-BFR—and, to a lower extent, RSH—resulted in impaired performance and a higher perceived strain than RSN. However, these 2 hypoxic methods do not seem to induce a long-lasting (post 24–48 h) physiological stress in elite badminton players.
Pedro L. Valenzuela, Carlos Amo, Guillermo Sánchez-Martínez, Elaia Torrontegi, Javier Vázquez-Carrión, Zigor Montalvo, Alejandro Lucia, and Pedro de la Villa
Purpose: To determine if transcranial direct-current stimulation (tDCS) could be effective for the enhancement of swimming performance or mood state in elite athletes. Methods : Eight male elite triathletes (age = 20  y, maximal oxygen uptake = 71  mL·kg−1·min−1) participated in this crossover, counterbalanced, sham-controlled, double-blind study. Participants received either actual (20 min of anodal stimulation of the motor cortex at 2 mA) or sham tDCS and performed an 800-m swimming test in which rating of perceived exertion and blood lactate response were measured. Mood state (Brunel Mood Scale) was assessed before and after each tDCS session and after the swimming test. Heart-rate variability and central nervous system readiness were assessed before and after each tDCS session. The chances of finding differences between conditions were determined using magnitude-based inferences. Results : A significant and very likely higher Brunel Mood Scale–determined vigor self-perception was found with actual tDCS after the stimulation session (−0.1 [1.2] and 2.0 [2.3] for sham and actual tDCS, respectively; P = .018, effect size = 1.14) and after exercise (−4.1 [2.9] and −0.9 [3.6] for sham and actual tDCS, respectively; P = .022, effect size = 0.98). However, likely trivial and nonsignificant (P > .05) differences were found between conditions in performance (599  s and 596  s, respectively). Unclear and nonsignificant differences were observed between conditions for the rest of the study end points. Conclusions : tDCS elicited a marked increase in vigor self-perception that was maintained after exercise but failed to improve swimming performance in elite triathletes.