Browse

You are looking at 71 - 80 of 4,425 items for :

  • Sport and Exercise Science/Kinesiology x
  • Physical Education and Coaching x
Clear All
Restricted access

Carl Persson, Flinn Shiel, Mike Climstein and James Furness

Dual-energy X-ray absorptiometry is a commonly used clinical assessment tool for body composition and bone mineral density, which is gaining popularity in athletic cohorts. Results from body composition scans are useful for athletic populations to track training and nutritional interventions, while bone mineral density scans are valuable for athletes at risk of developing stress fractures due to low bone mineral density. However, no research has ascertained if a novice technician (accredited but not experienced) could produce similar results to an experienced technician. Two groups of recreational athletes were scanned, one by an experienced technician, one by a novice technician. All participants were scanned twice with repositioning between scans. The experienced technician’s reliability (intraclass correlation coefficient = .989–.998; percentage change in mean = −0.01 to 0.10), precision (typical error as coefficient of variation percentage = 0.01–0.47; SEM% = 0.61–1.39), and sensitivity to change (smallest real difference percentage = 1.70–3.85) were similar; however, superior to those of the novice technician. The novice technician results were reliability (intraclass correlation coefficient = .985–.997; percentage change in mean = −0.03 to 0.23), precision (typical error as coefficient of variation percentage = 0.03–0.75; SEM% = 1.06–2.12), and sensitivity to change (smallest real difference percentage = 2.73–5.86). Extensive experience, while valuable, is not a necessary requirement to produce quality results when undertaking whole-body dual-energy X-ray absorptiometry scanning.

Restricted access

Júlio A. Costa, João Brito, Fábio Y. Nakamura, Eduardo M. Oliveira, Ovidio P. Costa and António N. Rebelo

Purpose: To analyze whether exercise training conducted at night disturbs sleep and affects nocturnal cardiac autonomic control in high-level female athletes. Methods: A total of 18 high-level female soccer players (mean [SD] age 20.4 [2.1] y) wore actigraphs and heart-rate (HR) monitors during night sleep throughout night training days (n = 8) and resting days (n = 8), for 3 consecutive weeks. This was a longitudinal study that measured internal training load, sleep, nocturnal cardiac autonomic activity, and well-being ratings prior to training sessions. Results: Training load varied across training days (eg, training impulse range, mean [SD]; effect size, ES [95% confidence interval]: 72.9 [18.8] to 138.4 [29.6] a.u.; F 4,62 = 32.331; ηp2=.673 [.001–.16], large effect; P < .001). However, no differences in subjective well-being ratings were observed, although ES was large. Total sleep time (training days vs resting days: 07:17 [00:47] h vs 07:51 [00:42] h; ES = 0.742 [0.59–0.92], P = .005; moderate effect) and sleep-onset time (00:58 [00:19] h vs 00:44 [00:16] h; ES = 0.802 [0.68–0.94], P = .001; moderate effect) were negatively affected after night training. In addition, small effects were detected for wake-up time, time in bed, and sleep latency (P > .05). No differences were detected in HR variability during sleep (range of lnRMSSD: 4.3 [0.4] to 4.5 [0.4] ln[ms] vs 4.6 [0.3] to 4.5 [0.4] ln[ms]; F 3,52 = 2.148; P > .05; ηp2=.112 [.01–.25], medium effect), but HR during sleep was significantly higher after training days (range of HR: 56 [4] to 63 [7] beats/min vs 54 [4] to 57 [6] beats/min; F 2,32 = 15.956; P < .001; ηp2=.484 [.20–.63], large effect). Conclusion: Overall, the results indicate that exercise training conducted at night may disturb sleep and affect HR, whereas limited effects can be expected in HR variability assessed during sleep in high-level female soccer players.

Restricted access

Simon Gavanda, Stephan Geisler, Oliver Jan Quittmann and Thorsten Schiffer

Purpose: Muscle mass, strength, and power are important factors for performance. To improve these characteristics, periodized resistance training is used. However, there is no consensus regarding the most effective periodization model. Therefore, the purpose of this study was to compare the effects of block (BLOCK) vs daily undulating periodization (DUP) on body composition, hypertrophy, strength, performance, and power in adolescent American football players. Methods: A total of 47 subjects participated in this study (mean [SD] age = 17 [0.8] y, strength training experience = 0.93 [0.99] y). Premeasurements and postmeasurements consisted of body mass (BM); fat mass; relative fat mass; fat-free mass (FFM); muscle mass (MM); muscle thickness of the vastus lateralis (VL), rectus femoris (RF), and triceps brachii (TB); 1-repetition-maximum back squat (BS) and bench press (BP); countermovement jump (CMJ); estimated peak power (Wpeak) from vertical jump performance; medicine-ball put (MBP); and 40-yd sprint. Subjects were randomly assigned in either the BLOCK or DUP group prior to the 12-wk intervention period consisting of 3 full-body sessions per week. Results: Both groups displayed significantly higher BM (P < .001), FFM (P < .001), MM (P < .001), RF (P < .001), VL (P < .001), TB (P < .001), BS (P < .001), BP (P < .001), CMJ (P < .001), Wpeak (P < .001), and MBP (P < .001) and significantly lower sprint times (P < .001) after 12 wk of resistance training, with no difference between groups. Conclusions: Resistance training was effective to increase muscle mass, strength, power, and performance in adolescent athletes. BLOCK and DUP affect anthropometric measures and physical performance equally.

Restricted access

Pål Haugnes, Per-Øyvind Torvik, Gertjan Ettema, Jan Kocbach and Øyvind Sandbakk

Purpose: To investigate the contribution from maximal speed (Vmax) and %Vmax to the finish sprint speed obtained in a cross-country sprint in the classical and skating style, as well as the coinciding changes in kinematic patterns and the effect of pacing strategy on the %Vmax. Methods: Twelve elite male cross-country skiers performed two 80-m Vmax tests on flat terrain using the classical double-poling and skating G3 techniques, followed by 4 simulated 1.4-km sprint time trials, performed with conservative (controlled start) and positive (hard start) pacing strategies in both styles with a randomized order. In all cases, these time trials were finalized by sprinting maximally over the last 80 m (the Vmax section). Results: Approximately 85% of Vmax was obtained in the finish sprint of the 1.4-km competitions, with Vmax and %Vmax contributing similarly (R 2 = 51–78%) to explain the overall variance in finish sprint speed in all 4 cases (P < .05). The changes in kinematic pattern from the Vmax to the finish sprint included 11–22% reduced cycle rate in both styles (P < .01), without any changes in cycle length. A 3.6% faster finish sprint speed, explained by higher cycle rate, was found by conservative pacing in classic style (P < .001), whereas no difference was seen in skating. Conclusions: Vmax ability and %Vmax contributed similarly to explain the finish sprint speed, both in the classic and skating styles, and independent of pacing strategy. Therefore, sprint cross-country skiers should concurrently develop both these capacities and employ technical strategies where a high cycle rate can be sustained when fatigue occurs.

Restricted access

Martina A. Maggioni, Matteo Bonato, Alexander Stahn, Antonio La Torre, Luca Agnello, Gianluca Vernillo, Carlo Castagna and Giampiero Merati

Purpose: To investigate the effects of ball drills and repeated-sprint-ability training during the regular season in basketball players. Methods: A total of 30 players were randomized into 3 groups: ball-drills training (BDT, n = 12, 4 × 4 min, 3 vs 3 with 3-min passive recovery), repeated-sprint-ability training (RSAT, n = 9, 3 × 6 × 20-m shuttle running with 20-s and 4-min recovery), and general basketball training (n = 9, basketball technical/tactical exercises), as control group. Players were tested before and after 8 wk of training using the following tests: V˙O2max, squat jump, countermovement jump, Yo-Yo Intermittent Recovery Test Level 1 (YIRT1), agility T test, line-drill test, 5-/10-/20-m sprints, and blood lactate concentration. A custom-developed survey was used to analyze players’ technical skills. Results: After training, significant improvements were seen in YIRT1 (BDT P = .014, effect size [ES] ± 90% CI = 0.8 ± 0.3; RSAT P = .022, ES ± 90% CI = 0.7 ± 0.3), the agility T test (BDT P = .018, ES ± 90% CI = 0.7 ± 0.5; RSAT P = .037, ES ± 90% CI = 0.7 ± 0.5), and the line-drill test (BDT P = .010, ES ± 90% CI = 0.3 ± 0.1; RSAT P < .0001, ES ± 90% CI = 0.4 ± 0.1). In the RSAT group, only 10-m sprint speeds (P = .039, ES ± 90% CI = 0.3 ± 0.2) and blood lactate concentration (P = .004, ES ± 90% CI = 0.8 ± 1.1) were improved. Finally, technical skills were increased in BDT regarding dribbling (P = .038, ES ± 90% CI = 0.8 ± 0.6), shooting (P = .036, ES ± 90% CI = 0.8 ± 0.8), passing (P = .034, ES ± 90% CI = 0.9 ± 0.3), rebounding (P = .023, ES ± 90% CI = 1.1 ± 0.3), defense (P = .042, ES ± 90% CI = 0.5 ± 0.5), and offense (P = .044, ES ± 90% CI = 0.4 ± 0.4) skills. Conclusions: BDT and RSAT are both effective in improving the physical performance of basketball players. BDT had also a positive impact on technical skills. Basketball strength and conditioning professionals should include BDT as a routine tool to improve technical skills and physical performance simultaneously throughout the regular training season.

Restricted access

John Molphy, John W. Dickinson, Neil J. Chester, Mike Loosemore and Gregory Whyte

Terbutaline is a prohibited drug except for athletes with a therapeutic use exemption certificate; terbutaline’s effects on endurance performance are relatively unknown. Purpose: To investigate the effects of 2 therapeutic (2 and 4 mg) inhaled doses of terbutaline on 3-km running time-trial performance. Methods: A total of 8 men (age 24.3 [2.4] y; weight 77.6 [8] kg; and height 179.5 [4.3] cm) and 8 women (age 22.4 [3] y; weight 58.6 [6] kg; and height 163 [9.2] cm) free from respiratory disease and illness provided written informed consent. Participants completed 3-km running time trials on a nonmotorized treadmill on 3 separate occasions following placebo and 2- and 4-mg inhaled terbutaline in a single-blind, repeated-measures design. Urine samples (15 min postexercise) were analyzed for terbutaline concentration. Data were analyzed using 1-way repeated-measures analysis of variance, and significance was set at P < .05 for all analyses. Results: No differences were observed for completion times (1103 [201] s, 1106 [195] s, 1098 [165] s; P = .913) for the placebo or 2- and 4-mg inhaled trials, respectively. Lactate values were higher (P = .02) after 4 mg terbutaline (10.7 [2.3] mmol·L−1) vs placebo (8.9 [1.8] mmol·L−1). Values of forced expiratory volume in the first second of expiration (FEV1) were greater after inhalation of 2 mg (5.08 [0.2]; P = .01) and 4 mg terbutaline (5.07 [0.2]; P = .02) compared with placebo (4.83 [0.5] L) postinhalation. Urinary terbutaline concentrations were mean 306 (288) ng·mL−1 and 435 (410) ng·mL−1 (P = .2) and peak 956 ng·mL−1 and 1244 ng·mL−1 after 2 and 4 mg inhaled terbutaline, respectively. No differences were observed between the male and female participants. Conclusions: Therapeutic dosing of terbutaline does not lead to an improvement in 3-km running performance despite significantly increased FEV1. The findings suggest that athletes using inhaled terbutaline at high therapeutic doses to treat asthma will not gain an ergogenic advantage during 3-km running performance.

Restricted access

Takeshi Kokubo, Yuta Komano, Ryohei Tsuji, Daisuke Fujiwara, Toshio Fujii and Osamu Kanauchi

The unique lactic acid bacteria, Lactococcus lactis strain plasma (LC-Plasma), stimulates plasmacytoid dendritic cells, which play an important role in viral infection. The authors previously reported that LC-Plasma reduced the number of days athletes experienced cold-like symptoms and fatigue feelings after high-intensity exercise training; however, the mechanism was unclear. In this study, the authors investigated the effect of LC-Plasma on recovery from physical damage after single exercise on a treadmill in BALB/c mice model. Oral administration of LC-Plasma (AIN-93G + 0.029% LC-Plasma) for 4 weeks significantly improved the locomotor reduction after treadmill exercise. This effect was not detected in mice receiving Lactobacillus rhamnosus GG, representative probiotics strain. LC-Plasma also improved voluntary locomotor activity after exercise. Blood and muscle sample analysis indicated that LC-Plasma affects plasmacytoid dendritic cell activation, which, in turn, attenuates muscle degenerative genes and the concentration of fatigue-controlled cytokine transforming growth factor-β.

Open access

Jos J. de Koning and Dionne A. Noordhof

Restricted access

Fiona Pelly and Susie Parker Simmons

Food provision at the Olympic Games has evolved considerably since the advent of a unified menu, but there are challenges in existing catering for the expanding cultural and sporting diversity. Continuity between events is difficult due to the changes in location, organizing committees, caterers, athletes, support staff, and volunteers. Independent review of the food provision by sports nutrition experts has been implemented to help establish some consistency between Olympic Games. The aim of this study was to compare an expert desk top and onsite review of the food provided at the Rio 2016 Olympic Games, and compare this with a similar review at the London 2012 Olympic Games. A previously developed survey was completed by sports nutrition experts 6 months prior to the opening of the Rio 2016 Olympic village and during the Olympic Games in September 2016. Questions about the food provision included both scaled and open-ended responses. There was a significantly lower rating for menu variety onsite (p = .025) versus the desk top review. All aspects of the menu and the ability to cater for specific situations rated as average or less. A significantly (p = .007) lower overall median rating was obtained for Rio (five out of 10) compared with London (eight out of 10), with hot gluten-free items rated as poor at both events. Comments from experts related to lack of variety, sports and recovery foods, absence of signage, and inaccurate nutrition labeling. An improved process for expert nutrition review at these events is warranted.

Restricted access

Jorge Carlos-Vivas, Elena Marín-Cascales, Tomás T. Freitas, Jorge Perez-Gomez and Pedro E. Alcaraz

Purpose: To describe the load–velocity relationship and the effects of increasing loads on spatiotemporal and derived kinetic variables of sprinting using weighted vests (WV) in soccer players and determining the load that maximizes power output. Methods: A total of 23 soccer players (age 20.8 [1.5] y) performed 10 maximal 30-m sprints wearing a WV with 5 different loads (0%, 10%, 20%, 30%, and 40% body mass [BM]). Sprint velocity and time were collected using a radar device and wireless photocells. Mechanical outputs were computed using a recently developed valid and reliable field method that estimates the step-averaged ground-reaction forces during overground sprint acceleration from anthropometric and spatiotemporal data. Raw velocity–time data were fitted by an exponential function and used to calculate the net horizontal ground-reaction forces and horizontal power output. Individual linear force–velocity relationships were then extrapolated to calculate the theoretical maximum horizontal force (F 0) and velocity and the ratio of force application (proportion of the total force production that is directed forward at sprint start). Results: Magnitude-based inferences showed an almost certain decrease in F 0 (effect size = 0.78–3.35), maximum power output (effect size = 0.78–3.81), and maximum ratio of force (effect size = 0.82–3.87) as the load increased. The greatest changes occurred with loads heavier than 20% BM, especially in ratio of force. In addition, the maximum power was achieved under unloaded conditions. Conclusions: Increasing load in WV sprinting affects spatiotemporal and kinetic variables. The greatest change in ratio of force happened with loads heavier than 20% BM. Thus, the authors recommend the use of loads ≤20% BM for WV sprinting.