RESUMEN
Our aim was to determine the effects of probiotic supplementation (Bifidobacterium longum 35624; 1 billion CFU·d-1) on exercise performance, immune modulation, and cognitive outlook in collegiate female athletes during six weeks of offseason training. Seventeen National Collegiate Athletic Association (NCAA) Division 1 collegiate female swimmers participated in this two-group matched, double-blind, placebo controlled design. Via stratified randomization, participants were assigned to probiotic (B. longum 35624; n = 8) or placebo (n = 9) groups. Pre, mid, and post-training, all participants completed exercise performance testing (aerobic/anaerobic swim time trials and force plate vertical jump) as well as provided serum (cytokine and gastrointestinal inflammatory markers) and salivary immunoglobulin A samples. Recovery-stress questionnaire for athletes (RESTQ-Sport) was administered at baseline and conclusion of each week. Data were analyzed by analysis of covariance (ANCOVA) by time point with the respective baseline values of each dependent variable being the covariate. No significant differences in exercise performance and biochemical markers were observed between groups following offseason training. Recovery-Stress Questionnaire for Athletes (RESTQ-sport) values in B. longum 35624 group had significantly higher (i.e., more desired; p < 0.05) values in sport recovery (weeks five and six) than placebo. Probiotic supplementation in collegiate female swimmers did not affect exercise performance or immune function throughout offseason training, but did indicate alterations in cognitive outlook.
RESUMEN
Pulling or pushing weighted sleds has been included in various exercise programs. Coaches and researchers may wish to calculate work performed or estimate forces during these exercises, which would involve calculating coefficients of friction: static friction coefficient (µs) and dynamic friction coefficient (µd). The purpose of this study was to establish a reliable method for determining µs, µd, and pulling forces while pulling a weighted sled with different loads to quantify horizontal forces and work performed for training, assessment, and/or research. A nylon tether was attached to a sled-mounted force transducer, and a winch was used to pull the tethered sled at a constant velocity for 20 seconds. Three different loads were pulled: 44.8 kg (the unloaded weight of the sled), 90.0 kg (44.8 kg sled with an additional load of 45.2 kg), and 136.2 kg (44.8 kg sled with an additional load of 91.4 kg). Each load was pulled 10 times using the winch for a total of 30 trials. The static friction coefficient (mean ± SD) was 0.47 ± 0.01 (coefficient of variation [CV] = 2.2%), 0.42 ± 0.01 (CV = 3.0%), and 0.39 ± 0.01 (CV = 2.7%), whereas dynamic friction coefficient (mean ± SD) was 0.35 ± 0.01 (CV = 1.6%), 0.33 ± 0.01 (CV = 3.7%), 0.31 ± 0.00 (CV = 1.0%) for 44.8, 90.0, and 136.2 kg, respectively (p < 0.01). When all trials and loads were combined, µs = 0.43 ± 0.04 and µd = 0.33 ± 0.02 with CV of 8.3 and 5.6%, respectively. The friction coefficients determined in this study were very repeatable, as indicated by the low CV. Coaches, athletes, and researchers who wish to determine µs and µd for their own specific equipment and surfaces can use the methods described here to do so.
