Kinesiology
A Comparison of Dehydration Techniques for Acute Weight Management in Rowing
Mild sauna dehydration and fluid abstinence were investigated as weight loss strategies for lightweight rowers. Rowers (N=12) performed a power test, an incremental VO2max test, and a visuomotor battery: once euhydrated, once following sauna dehydration (SAU), and once following fluid abstinence and then sauna dehydration (FA). The percent body mass change (%BMC) achieved, %BMC attributable to sauna dehydration, and %BMC attributable to fluid abstinence were used within linear mixed effects models to predict hydration and performance variables. Sauna and overnight dehydration exerted indistinguishable effects on plasma osmolality, urine osmolality and thirst (p > .05). Fluid abstinence but not sauna dehydration was related to lower power production on the power test (b = 12.14W / 1%BMC, FA = 673.46 ± 79.50, SAU = 683.33 ± 72.08, p = .029), a lower total wattage produced on the incremental VO2max test (b = 4261.51W / 1%BMC, FA = 71029.58 ± 16256.56, SAU = 74001.50 ± 14936.56, p = .006), lower wattages at 2 mmol/L (b = 27.84W / 1%BMC, FA = 180.74 ± 40.27, SAU = 190.82 ± 50.79, p < .001) and 4 mmol/L (b = 20.45W / 1%BMC, FA = 221.90 ± 52.62, SAU = 238.89 ± 40.78, p = .002) blood lactate, and slower movement time on a visuomotor task (b = -38.06ms / 1%BMC, p = .004). Mild fluid abstinence but not sauna dehydration reduces rowing performance when two-hour rehydration is allowed.
Author Keywords: crew, fluid, hydration, lightweight, sauna, weight
Using a real-world chopping task to study motor learning and memory
Typically task interference is studied using reaching adaptation tasks (visuomotor rotation and/or force-field learning). Participants in these experiments are already experts at the base task (point-to-point, planar reaching) and their ability to adapt reaching to the imposed perturbation is studied. The pattern of data induced by the perturbation is used to make inferences about the nature and neural correlates of our learning and memory for reaching perturbations, specifically, and motor performance in general. We wanted to see if it is possible to demonstrate this same interference pattern using a novel vegetable-chopping task, where we can easily recreate natural performance settings using a task for which we can easily identify non-experts. Participants performed a chopping task in which they are asked to chop a sweet potato into 5 mm-wide slices, matching the beat of a metronome (120 bpm). Following this initial learning, participants were exposed to an interference condition. Participants then performed trials of the original task again. Interference was inferred if the second performance of the original task was impaired, compared to initial performance. Experiment 1 involved novice choppers, and either the force or frequency of chops was manipulated. Only the altered frequency task produced interference effects. In Experiment 2, competent and expert choppers had to manage either a faster or slower frequency. We found evidence for interference in competents, but not experts. These results support the idea that the vulnerability to interference of motor memory changes with practice, and so any inferences made about memory structure must take into account not only expert performance, but every level of skill.
Author Keywords: expertise, interference, motor learning, reaching adaptation
How Do We Let the Players Play and Keep Them Safe? The Issue of Problematic Beliefs in the Prevention of Concussion Injury
Athletes' concussion risk is part of a complex system of personal and contextual factors. This study differentiated athletes based on attitudes and intentions towards protective behaviours. A cross-sectional survey design was used to sample varsity athletes. Three intention response subgroups (indifferent, reactive, and proactive) were identified. The indifferent group (28%) reported little-to-no intent to engage in risk reduction behaviours. These athletes reported lower belief in the efficacy of concussion management behaviours and greater risk acceptance attitudes. The proactive group (32%) reported intent to actively reduce personal concussion risk through engaging in behaviours such as confronting aggressive opponents about the risk they pose to others. The reactive group (40%) only reported intent to engage in concussion management behaviours. Indifferent athletes had the highest likelihood of concussion exposure followed by reactive athletes. The proactive athletes had the lowest likelihood. Concussion programs must address beliefs and intentions towards protective behaviours to improve effectiveness.
Author Keywords: Athlete, Attitudes, Concussion, Injury Prevention, Intentions, Risk