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Øyvind Skattebo, Thomas Losnegard and Hans Kristian Stadheim

Purpose: Long-distance cross-country skiers specialize to compete in races >50 km predominantly using double poling (DP). This emphasizes the need for highly developed upper-body endurance capacities and an efficient DP technique. The aim of this study was to investigate potential effects of specialization by comparing physiological capacities and kinematics in DP between long-distance skiers and skiers competing using both techniques (skating/classic) in several competition formats (“all-round skiers”). Methods: Seven male long-distance (32 [6] y, 183 [6] cm, 76 [5] kg) and 6 all-round (25 [3] y, 181 [5] cm, 75 [6] kg) skiers at high international levels conducted submaximal workloads and an incremental test to exhaustion for determination of peak oxygen uptake (VO2peak) and time to exhaustion (TTE) in DP and running. Results: In DP and running maximal tests, TTE showed no difference between groups. However, long-distance skiers had 5–6% lower VO2peak in running (81 [5] vs 85 [3] mL·kg−1·min−1; P = .07) and DP (73 [3] vs 78 [3] mL·kg−1·min−1; P < .01) than all-round skiers. In DP, long-distance skiers displayed lower submaximal O2 cost than all-round skiers (3.8 ± 3.6%; P < .05) without any major differences in cycle times or cyclic patterns of joint angles and center of mass. Lactate concentration over a wide range of speeds (45–85% of VO2peak) did not differ between groups, even though each workload corresponded to a slightly higher percentage of VO2peak for long-distance skiers (effect size: 0.30–0.68). Conclusions: The long-distance skiers displayed lower VO2peak but compensated with lower O2 cost to perform equally with the all-round skiers on a short TTE test in DP. Furthermore, similar submaximal lactate concentration and reduced O2 cost could be beneficial in sustaining high skiing speeds in long-duration competitions.

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Layne Case and Joonkoo Yun

Despite the rising interest in intervention for children with autism spectrum disorder, the extent to which interventions are effective on gross motor outcomes is currently unknown. The purpose of this study was to analyze the effect of different intervention approaches on gross motor outcomes among children with autism spectrum disorder using meta-analysis. A total of 18 studies met the inclusion criteria for quantitative analysis. Pre- and posttest means and SDs were extracted to calculate effect sizes. Potential moderator variables were chosen based on important intervention characteristics. The results suggest that interventions have a large effect on gross motor outcomes among children with autism spectrum disorder (δ = 0.99, SE = 0.19, p < .001, 95% confidence interval [0.62, 1.36]). The interventions that were 16 total hours or longer had a significantly larger effect than those less than 16 hr. In addition, the interventions in experimental settings had significantly larger effects than the interventions in practical settings. Future interventions should consider intensity, including not only the duration of the intervention but also the intensity in which specific intervention goals are targeted.

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Iva Obrusnikova, Haley M. Novak and Albert R. Cavalier

Adults with intellectual disability have significantly lower musculoskeletal fitness than their peers without a disability. Appropriate instructional strategies are needed to facilitate their acquisition and maintenance of musculoskeletal fitness. In this multiple-baseline across-participants single-subject study, the authors evaluated the effects of a multicomponent package that included a video-enhanced system of least-to-most prompts on the acquisition of 5 muscle-strengthening exercises in 3 women with mild intellectual disability, age 24–37 yr. Results show substantive gains in correct and independent performance of steps in the 5 exercises during the treatment condition. The improved performance was maintained 2 wk after the last treatment session and in a large YMCA gym. The study suggests that use of the video-enhanced system of least-to-most prompts can lead to improved acquisition and maintenance of muscle-strengthening exercises by adults with mild intellectual disability.

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Filip Sabol, Jozo Grgic and Pavle Mikulic

Purpose: To examine the acute effects of 3 doses of caffeine on upper- and lower-body ballistic exercise performance and to explore if habitual caffeine intake affects the acute effects of caffeine ingestion on ballistic exercise performance. Methods: Twenty recreationally active male participants completed medicine-ball-throw and vertical-jump tests under 4 experimental conditions (placebo and 2, 4, and 6 mg·kg−1 of caffeine). Results: One-way repeated-measures analysis of variance (ANOVA) with subsequent post hoc analyses indicated that performance in the medicine-ball-throw test improved, compared with placebo, only with a 6 mg·kg−1 dose of caffeine (P = .032). Effect size, calculated as the mean difference between the 2 measurements divided by the pooled SD, amounted to 0.29 (+3.7%). For the vertical-jump test, all 3 caffeine doses were effective (compared with placebo) for acute increases in performance (P values .022–.044, effect sizes 0.35–0.42, percentage changes +3.7% to +4.1%). A 2-way repeated-measures ANOVA indicated that there was no significant group × condition interaction effect, suggesting comparable responses between low (≤100 mg·d−1) and moderate to high (>100 mg·d−1) caffeine users to the experimental conditions. Conclusion: Caffeine doses of 2, 4, and 6 mg·kg−1 seem to be effective for acute enhancements in lower-body ballistic exercise performance in recreationally trained male individuals. For the upper-body ballistic exercise performance, only a caffeine dose of 6 mg·kg−1 seems to be effective. The acute effects of caffeine ingestion do not seem to be affected by habitual caffeine intake; however, this requires further exploration.

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Jonathon Weakley, Kevin Till, John Sampson, Harry Banyard, Cedric Leduc, Kyle Wilson, Greg Roe and Ben Jones

Purpose: Feedback can enhance acute physical performance. However, its effects on physical adaptation have received little attention. Therefore, the purpose of this study was to determine the effect of feedback during a 4-wk training program on jump, sprint, and strength adaptations. Methods: A total of 28 semiprofessional male rugby union players were strength-matched into 2 groups (feedback and nonfeedback). During the 4-wk training program, the Feedback group received immediate, objective feedback on (1) mean concentric velocity during resistance training repetitions, (2) distance feedback for standing broad jumps, and (3) time for sprints. The Nonfeedback group was not provided additional information. Across the 4-wk mesocycle, subjects completed 3 strength and conditioning sessions per week. Countermovement jump, standing long jump, 10- and 20-m sprint, and 3-repetition-maximum barbell back squat and bench press were measured before and after the training intervention. Magnitude-based inferences assessed meaningful changes within and between groups. Results: The Feedback group showed small to moderate improvements in outcome measures, whereas the Nonfeedback group demonstrated trivial to small improvements. Improvements in countermovement-jump relative peak power (effect size ± 90% confidence limits: 0.34 ± 0.42), 10-m (0.20 ± 0.35) and 20-m sprints (0.40 ± 0.21), and 3-repetition-maximum back squats (0.23 ± 0.17) were possibly to likely greater for the Feedback condition than for Nonfeedback. Conclusions: Providing augmented feedback during strength and conditioning routines can enhance training adaptations compared with athletes who do not receive feedback. Consequently, practitioners should consider providing kinematic outputs, displacement, or sprint time at the completion of each repetition as athletes train.

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Carlo Castagna, Stefano D’Ottavio, Stefano Cappelli and Susana Cristina Araújo Póvoas

Purpose: To examine the internal and external load imposed by long sprint ability–oriented small-sided games (SSG) using different ratios of players to pitch area (densities) in soccer players. Methods: A total of 19 professional soccer players from the same soccer club (age = 17.1 [0.3] y, height = 1.76 [0.69] m, and body mass = 69.7 [9.4] kg) participated in this study. Players performed 4 × 30-s (150 s recovery) all-out 1-vs-1 SSG considering 300, 200, and 100 m2 per player (48 h apart). Players’ external loads were tracked with global positioning technology (20 Hz). Heart rate, blood lactate concentration (BLc), and rating of perceived exertion characterized players’ internal load. Peak BLc was assessed with a 30-s all-out test on a nonmotorized treadmill (NMT). Results: SSG300 produced higher BLc than SSG200 (moderate) and SSG100 (large). The SSG300, SSG200, and SSG100 BLc were 97.8% (34.8%), trivial; 74.7% (24.9%), moderate; and 43.4% (15.7%), large, of the NMT30s peak BLc, respectively. Players covered more distance at high intensity during the SSG300 than in other SSG conditions (huge to very large differences). High-intensity deceleration distance was largely lower in SSG200 than in SSG300. SSG100 elicited very large to huge and large to very large lower external load values than SSG300 and SSG200, respectively. Conclusions: The main finding of this study showed an inverse association between ball-drill density and internal/external loads in long sprint ability–oriented SSG. The SSG300 provided BLc closer to individual maximal, thus satisfying the all-out construct assumed for the development of long sprint ability. Further studies using the SSG300 as a training intervention and/or investigating other different SSG formats using the same density are warranted.

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Achraf Ammar, Stephen J. Bailey, Omar Hammouda, Khaled Trabelsi, Nabil Merzigui, Kais El Abed, Tarak Driss, Anita Hökelmann, Fatma Ayadi, Hamdi Chtourou, Adnen Gharbi and Mouna Turki

Purpose: The effect of playing surface on physical performance during a repeated-sprint ability (RSA) test and the mechanisms for any potential playing-surface-dependent effects on RSA performance are equivocal. The purpose of this study was to investigate the effect of natural grass (NG) and artificial turf (AT) on physical performance, ratings of perceived exertion, feeling scale, and blood biomarkers related to anaerobic contribution (blood lactate [Lac]), muscle damage (creatine kinase and lactate dehydrogenase), inflammation (C-reactive protein), and immune function (neutrophils [NEU], lymphocytes [LYM], and monocytes) in response to an RSA test. Methods: A total of 9 male professional football players from the same regional team completed 2 sessions of RSA testing (6 × 30 s interspersed with a 35-s recovery) on NG and AT in a randomized order. During the RSA test, total (sum of distances) and peak (highest distance covered in a single repetition) distance covered were determined using a measuring tape, and the decrement in sprinting performance from the first to the last repetition was calculated. Before and after the RSA test, ratings of perceived exertion, feeling scale, and Lac, creatine kinase, lactate dehydrogenase, C-reactive protein, NEU, LYM, and monocytes were recorded in both NG and AT conditions. Results: Although physical performance declined during the RSA blocks on both surfaces (P = .001), the distance covered declined more on NG (15%) than on AT (11%; P = .04; effect size [ES] = −0.34; 95% confidence interval [CI], −1.21 to 0.56) with a higher total distance covered (+6% [2%]) on AT (P = .018; ES = 1.15; 95% CI, 0.16 to 2.04). In addition, lower ratings of perceived exertion (P = .04; ES = −0.49; 95% CI, −1.36 to 0.42), Lac, NEU, and LYM (P = .03; ES = −0.80; 95% CI, −1.67 to 0.14; ES = −0.16; 95% CI, −1.03 to 0.72; and ES = −0.94; 95% CI, −1.82 to 0.02, respectively) and more positive feelings (P = .02; ES = 0.81; 95% CI, −0.13 to 1.69) were observed after the RSA test performed on AT than on NG. No differences were observed in the remaining physical and blood markers. Conclusion: These findings suggest that RSA performance is enhanced on AT compared with NG. This effect was accompanied by lower fatigue perception and Lac, NEU, and LYM and a more pleasurable feeling. These observations might have implications for physical performance in intermittent team-sport athletes who train and compete on different playing surfaces.

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Leah S. Goudy, Brandon Rhett Rigby, Lisa Silliman-French and Kevin A. Becker

The purpose of this study was to determine changes in balance, postural sway, and quality of life after 6 wk of simulated horseback riding in adults diagnosed with Parkinson’s disease. Eight older adults completed two 60-min riding sessions weekly for 6 wk. Variables of balance, postural sway, and quality of life were measured 6 wks before and within 1 wk before and after the intervention. Berg Balance Scale scores decreased from baseline to preintervention (48.36 ± 5.97 vs. 45.86 ± 6.42, p = .050) and increased from preintervention to postintervention (45.86 ± 6.42 vs. 50.00 ± 4.38, p = .002). Cognitive impairment, a dimension of quality of life, improved from baseline to postintervention (37.5 ± 20.5 vs. 21.5 ± 14.4, p = .007). Six weeks of simulated horseback riding may improve balance and cognitive impairment in older adults with Parkinson’s disease.

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Susan Y. Kwiecien, Malachy P. McHugh, Stuart Goodall, Kirsty M. Hicks, Angus M. Hunter and Glyn Howatson

Purpose: To evaluate the effectiveness between cold-water immersion (CWI) and phase-change-material (PCM) cooling on intramuscular, core, and skin-temperature and cardiovascular responses. Methods: In a randomized, crossover design, 11 men completed 15 min of 15°C CWI to the umbilicus and 2-h recovery or 3 h of 15°C PCM covering the quadriceps and 1 h of recovery, separated by 24 h. Vastus lateralis intramuscular temperature at 1 and 3 cm, core and skin temperature, heart-rate variability, and thermal comfort were recorded at baseline and 15-min intervals throughout treatment and recovery. Results: Intramuscular temperature decreased (P < .001) during and after both treatments. A faster initial effect was observed from 15 min of CWI (Δ: 4.3°C [1.7°C] 1 cm; 5.5°C [2.1°C] 3 cm; P = .01). However, over time (2 h 15 min), greater effects were observed from prolonged PCM treatment (Δ: 4.2°C [1.9°C] 1 cm; 2.2°C [2.2°C] 3 cm; treatment × time, P = .0001). During the first hour of recovery from both treatments, intramuscular temperature was higher from CWI at 1 cm (P = .013) but not 3 cm. Core temperature deceased 0.25° (0.32°) from CWI (P = .001) and 0.28°C (0.27°C) from PCM (P = .0001), whereas heart-rate variability increased during both treatments (P = .001), with no differences between treatments. Conclusions: The magnitude of temperature reduction from CWI was comparable with PCM, but intramuscular temperature was decreased for longer during PCM. PCM cooling packs offer an alternative for delivering prolonged cooling whenever application of CWI is impractical while also exerting a central effect on core temperature and heart rate.