Browse

You are looking at 91 - 100 of 16,998 items for :

  • Sport and Exercise Science/Kinesiology x
  • All content x
Clear All
Restricted access

Eszter Somogyi, Laurent Salomon, and Jacqueline Fagard

As a step toward understanding the developmental relationship between handedness and language lateralization, this longitudinal study investigated how infants (N = 21) move their hands in noncommunicative and communicative situations at 2 weeks and at 3 months of age. The authors looked at whether left-right asymmetry in hand movements and in duration of self-touch appeared across conditions and whether the direction of asymmetry depended on the communicative nature of the situation. The authors found that asymmetries appeared less consistently than suggested in literature and did not only depend on the communicative nature of the situation. Instead, hand activity and self-touch patterns depended on age, the presence of the mother, the degree of novelty of the situation, and the presence of an object. The results partly support previous studies that pointed out an early differentiation of communicative hand movements versus noncommunicative ones in infants. It is in terms of the amount of global hand activity, rather than in those of the laterality of hand movements that this differentiation emerged in this study. At 3 months, infants moved their hands more in the communicative conditions than in the noncommunicative conditions and this difference appeared as a tendency already at 2 weeks of age.

Restricted access

Ernst Albin Hansen

Investigations of behavior and control of voluntary stereotyped rhythmic movement contribute to the enhancement of motor function and performance of disabled, sick, injured, healthy, and exercising humans. The present article presents examples of unprompted alteration of freely chosen movement rate during voluntary stereotyped rhythmic movements. The examples, in the form of both increases and decreases of movement rate, are taken from activities of cycling, finger tapping, and locomotion. It is described that, for example, strength training, changed power output, repeated bouts, and changed locomotion speed can elicit an unprompted alteration of freely chosen movement rate. The discussion of the examples is based on a tripartite interplay between descending drive, rhythm-generating spinal neural networks, and sensory feedback, as well as terminology from dynamic systems theory.

Restricted access

Ed Maunder, Deborah K. Dulson, and David M. Shaw

Purpose: Considerable interindividual heterogeneity has been observed in endurance performance responses following induction of a ketogenic diet (KD). It is plausible that a physiological stress response in the period following the dramatic dietary shift associated with transition to a KD may explain this heterogeneity. Methods: In a randomized, crossover study design, 8 trained male runners completed an incremental exercise test and ran to exhaustion at 70%VO2max before and after a 31-day rigorously controlled habitual diet or KD intervention, and recorded heart rate variability (root mean square of the sum of successive differences in R–R intervals [rMSSD]) upon waking each morning along with the recovery–stress questionnaire for athletes each week. Data were analyzed using linear mixed models. Results: A significant reduction in rMSSD was observed in the KD (−9.77 [4.03] ms, P = .02), along with an increase in day-to-day variability in rMSSD (2.1% [1.0%], P = .03). The reduction in rMSSD in the KD for the subgroup of individuals exhibiting impaired exercise capacity following induction of the KD approached significance (Δ −22 [15] ms, P = .06, N = 4); whereas no effect was observed in those who exhibited unchanged exercise capacity (Δ 5 [18] ms, P = .61, N = 4). No main effects were observed for recovery–stress questionnaire for athletes. Conclusions: Our data suggest those working with endurance athletes transitioning onto a KD may consider using noninvasive, inexpensive resting heart rate variability measures to gain individual-level insights into the likely short-term effects on exercise capacity.

Restricted access

Pedro L. Valenzuela, Fernando Rivas, and Guillermo Sánchez-Martínez

Purpose: To describe the effects of COVID-19 lockdown and a subsequent retraining on the training workloads, autonomic responses, and performance of a group of elite athletes. Methods: The training workloads and heart rate variability (assessed through the log-transformed root mean square of successive R–R intervals) of 7 elite badminton players were registered daily during 4 weeks of normal training (baseline), 7 to 10 weeks of lockdown, and 6 to 8 weeks of retraining. Physical performance was assessed at baseline and after each phase by means of a countermovement jump and the estimated squat 1-repetition maximum. Results: A reduction in training workloads was observed in all participants during the lockdown (−63.7%), which was accompanied by a reduced heart rate variability in all but one participant (−2.0%). A significant reduction was also observed for countermovement jump (−6.5%) and 1-repetition maximum performance (−11.5%), which decreased in all but one participant after the lockdown. However, after the retraining phase, all measures returned to similar values to those found at baseline. At the individual level, there were divergent responses, as exemplified by one athlete who attenuated the reduction in training workloads and increased her performance during the lockdown and another one who markedly reduced his workload and performance, and got injured during the retraining phase. Conclusions: Although there seems to be a large interindividual variability, COVID-19 lockdown is likely to impose negative consequences on elite athletes, but these detrimental effects might be avoided by attenuating reductions in training workloads and seem to be overall recovered after 6 to 8 weeks of retraining.

Restricted access

Adam Mallett, Phillip Bellinger, Wim Derave, Katie McGibbon, Eline Lievens, Ben Kennedy, Hal Rice, and Clare Minahan

Purpose: To determine the influence of muscle fiber typology (MFT) on the pacing strategy of elite swimmers competing in the 200-m freestyle event. Method: The top 3 career-best performances from 25 elite 200-m freestyle swimmers were analyzed—12 women (1:58.0 [0:01.3] min:s) and 13 men (1:48.4 [0:02.5]). Muscle carnosine concentration was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and soleus muscles and expressed as a carnosine aggregate z score (CAZ score) relative to an age- and gender-matched nonathlete control group to estimate MFT. Linear regression models were employed to examine the influence of MFT on the percentage of overall race time spent in each 50-m lap. Results: Swimmers with a higher CAZ score spent a greater percentage of race time in lap 3 compared with swimmers with a lower CAZ score (0.1%, 0.0% to 0.2%; mean, 90% confidence interval, P = .02). For every 1% increase in the percentage of race time spent in lap 1, the percentage of race time spent in lap 3 decreased by 0.4% for swimmers with a higher CAZ score (0.2% to −0.5%, P = .00, r = −.51), but not for swimmers with a lower CAZ score (−0.1%, −0.3% to 0.1%, P = .28, r = −.18). The percentage of race time spent in lap 4 decreased by 0.8% for higher-CAZ-score swimmers (−0.5% to −1.0%, P = .00, r = −.66) and by 0.9% for lower-CAZ-score swimmers (−0.6% to −1.3%, P = .00, r = −.65) when lap 1 percentage increased by 1%. Conclusion: MFT may influence the pacing strategy of swimmers in the 200-m freestyle event, which provides an avenue for maximizing individualized pacing strategies of elite swimmers.

Restricted access

Filippo Dolci, Andrew E. Kilding, Tania Spiteri, Paola Chivers, Ben Piggott, Andrew Maiorana, and Nicolas H. Hart

Purpose: To investigate the acute effect of repeated-sprint activity (RSA) on change-of-direction economy (assessed using shuttle running economy [SRE]) in soccer players and explore neuromuscular and cardiorespiratory characteristics that may modulate this effect. Methods: Eleven young elite male soccer players (18.5 [1.4] y old) were tested on 2 different days during a 2-week period in their preseason. On day 1, lower-body stiffness, power and force were assessed via countermovement jumps, followed by an incremental treadmill test to exhaustion to measure maximal aerobic capacity. On day 2, 2 SRE tests were performed before and after a repeated-sprint protocol with heart rate, minute ventilation, and blood lactate measured. Results: Pooled group analysis indicated no significant changes for SRE following RSA due to variability in individual responses, with a potentiation or impairment effect of up to 4.5% evident across soccer players. The SRE responses to RSA were significantly and largely correlated to players’ lower-body stiffness (r = .670; P = .024), and moderately (but not significantly) correlated to players’ force production (r = −.455; P = .237) and blood lactate after RSA (r = .327; P = .326). Conclusions: In summary, SRE response to RSA in elite male soccer players appears to be highly individual. Higher lower-body stiffness appears as a relevant physical contributor to preserve or improve SRE following RSA.

Restricted access

Mehdi Kordi, Len Parker Simpson, Kevin Thomas, Stuart Goodall, Tom Maden-Wilkinson, Campbell Menzies, and Glyn Howatson

Purpose: To assess the association between the W′ and measures of neuromuscular function relating to the capacity of skeletal muscle to produce force in a group of elite cyclists. Methods: Twenty-two athletes specializing in a range of disciplines and competing internationally volunteered to participate. Athletes completed assessments of maximum voluntary torque (MVT), voluntary activation, and isometric maximum voluntary contraction to measure rate of torque development (RTD). This was followed by assessment of peak power output (PPO) and 3-, 5-, and 12-minute time trials to determine critical power. Pearson correlation was used to examine associations with critical power and W′. Goodness of fit was calculated, and significant relationships were included in a linear stepwise regression model. Results: Significant positive relationships were evident between W′ and MVT (r = .82), PPO (r = .70), and RTD at 200 milliseconds (r = .59) but not with RTD at 50 milliseconds and voluntary activation. Correlations were also observed between critical power and RTD at 200 milliseconds and MVT (r = .54 and r = .51, respectively) but not with PPO, voluntary activation, or RTD at 50 milliseconds. The regression analysis found that 87% of the variability in W′ (F 1,18 = 68.75; P < .001) was explained by 2 variables: MVT (81%) and PPO (6%). Conclusions: It is likely that muscle size and strength, as opposed to neural factors, contribute meaningfully to W′. These data can be used to establish training methods to enhance W′ to improve cycling performance in well-trained athletes.

Restricted access

Karlee Naumann, Jocelyn Kernot, Gaynor Parfitt, Bethany Gower, and Kade Davison

The purpose of this study was to produce a descriptive overview of the types of water-based interventions for people with neurological disability, autism, and intellectual disability and to determine how outcomes have been evaluated. Literature was searched through MEDLINE, EMBASE, Ovid Emcare, SPORTDiscus, Google Scholar, and Google. One hundred fifty-three papers met the inclusion criteria, 115 hydrotherapy, 62 swimming, 18 SCUBA (self-contained underwater breathing apparatus), and 18 other water-based interventions. Common conditions included cerebral palsy, spinal cord injury, Parkinson’s disease, and intellectual disability. Fifty-four papers explored physical outcomes, 36 psychosocial outcomes, and 24 both physical and psychosocial outcomes, with 180 different outcome measures reported. Overall, there is a lack of high-quality evidence for all intervention types. This review provides a broad picture of water-based interventions and associated research. Future research, guided by this scoping review, will allow a greater understanding of the potential benefits for people with neurological disability, autism, and intellectual disability.

Restricted access

Raphael M. Cunha, Gisela Arsa, Iransé Oliveira-Silva, Izabela Ferreira Rocha, and Alexandre Machado Lehnen

This study investigated the acute blood pressure (BP) effects of different exercise modalities in older adults with hypertension. Sixty volunteers were randomly assigned (n = 15/group) into different exercise protocols: resistance, bike, water-based exercise (WE), and a control session—all for ∼45 min. Clinic BP measurements were taken before, immediately after, and 15 and 30 min after protocols. The data were analyzed by one-way analysis of variance; generalized estimating equations, following Bonferroni post hoc (p < .05). Immediately after exercise, the systolic BP (SBP) increased in all exercise protocols (resistance exercise = Δ10.3, bike exercise = Δ5.8, WE = Δ9.5 mmHg; p < .001), while the diastolic BP was not altered. Afterward, the SBP reached the value observed before exercise. In Minute 30, only WE presented a significant reduction for SBP (WE = Δ−4.6 mmHg; p < .05). This study has important clinical implications in hemodynamic safety for acute BP increases immediately after exercises, as well as, in the SBP, reduction benefits for older adults with hypertension.

Restricted access

Kiarri N. Kershaw, Derek J. Marsh, Emma G. Crenshaw, Rebecca B. McNeil, Victoria L. Pemberton, Sabrina A. Cordon, David M. Haas, Michelle P. Debbink, Brian M. Mercer, Samuel Parry, Uma Reddy, George Saade, Hyagriv Simhan, Ronald J. Wapner, Deborah A. Wing, William A. Grobman, and for the NICHD nuMoM2b and NHLBI nuMoM2b Heart Health Study Networks

Background: Several features of the neighborhood built environment have been shown to promote leisure-time physical activity (PA) in the general population, but few studies have examined its impact on PA during pregnancy. Methods: Data were extracted from 8362 Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be cohort participants (2010–2013). Residential address information was linked to 3 built environment characteristics: number of gyms and recreation areas within a 3-km radius of residence and census block level walkability. Self-reported leisure-time PA was measured in each trimester and dichotomized as meeting PA guidelines or not. Relative risks for cross-sectional associations between neighborhood characteristics and meeting PA guidelines were estimated using Poisson regression. Results: More gyms and recreation areas were each associated with a greater chance of meeting PA guidelines in models adjusted for sociodemographic characteristics and preexisting conditions. Associations were strongest in the third trimester where each doubling in counts of gyms and recreation areas was associated with 10% (95% confidence interval, 1.07–1.13) and 8% (95% confidence interval, 1.03–1.12), respectively, greater likelihood of meeting PA guidelines. Associations were similar though weaker for walkability. Conclusions: Results from a large, multisite cohort suggest that these built environment characteristics have similar PA-promoting benefits in pregnant women as seen in more general populations.