spike jump biomechanics in male versus female elite volleyball players

ABSTRACTThere are well-known biological differences between women and men, especially in technical-coordinative variations that contribute to sex differences in performance of complex movements lik..

Investigating the correlation between paediatric stride interval persistence and gross energy expenditure

<p>Abstract</p> <p>Background</p> <p>Stride interval persistence, a term used to describe the correlation structure of stride interval time series, is thought to provide insight into neuromotor control, though its exact clinical meaning has not yet been realized. Since human locomotion is shaped by energy efficient movements, it has been hypothesized that stride interval dynamics and energy expenditure may be inherently tied, both having demonstrated similar sensitivities to age, disease, and pace-constrained walking.</p> <p>Findings</p> <p>This study tested for correlations between stride interval persistence and measures of energy expenditure including mass-specific gross oxygen consumption per minute (<inline-formula><graphic file="1756-0500-3-47-i1.gif"/></inline-formula>), mass-specific gross oxygen cost per meter (<it>VO</it>₂) and heart rate (HR). Metabolic and stride interval data were collected from 30 asymptomatic children who completed one 10-minute walking trial under each of the following conditions: (i) overground walking, (ii) hands-free treadmill walking, and (iii) handrail-supported treadmill walking. Stride interval persistence was not significantly correlated with <inline-formula><graphic file="1756-0500-3-47-i1.gif"/></inline-formula> (p > 0.32), <it>VO</it>₂(p > 0.18) or HR (p > 0.56).</p> <p>Conclusions</p> <p>No simple linear dependence exists between stride interval persistence and measures of gross energy expenditure in asymptomatic children when walking overground and on a treadmill.</p

Normative data on regional sweat-sodium concentrations of professional male team-sport athletes

Background: The purpose of this paper was to report normative data on regional sweat sweat-sodium concentrations of various professional male team-sport athletes, and to compare sweat-sodium concentrations among sports. Data to this effect would inform our understanding of athlete sodium requirements, thus allowing for the individualisation of sodium replacement strategies. Accordingly, data from 696 athletes (Soccer, n = 270; Rugby, n = 181; Baseball, n = 133; American Football, n = 60; Basketball, n = 52) were compiled for a retrospective analysis. Regional sweat-sodium concentrations were collected using the pilocarpine iontophoresis method, and compared to self-reported measures collected via questionnaire. Results: Sweat-sodium concentrations were significantly higher (p < 0.05) in American football (50.4 ± 15.3 mmol·L-1), baseball (54.0 ± 14.0 mmol·L-1), and basketball (48.3 ± 14.0 mmol·L-1) than either soccer (43.2 ± 12.0 mmol·L-1) or rugby (44.0 ± 12.1 mmol·L-1), but with no differences among the N.American or British sports. There were strong positive correlations between sweat-sodium concentrations and self-reported sodium losses in American football (rs = 0.962, p < 0.001), basketball (rs = 0.953, p < 0.001), rugby (rs = 0.813, p < 0.001), and soccer (rs = 0.748, p < 0.001). Conclusions: The normative data provided on sweat-sodium concentrations might assist sports science/medicine practitioners in generating bespoke hydration and electrolyte-replacement strategies to meet the sodium demands of professional team-sport athletes. Moreover, these novel data suggest that self-reported measures of sodium loss might serve as an effective surrogate in the absence of direct measures; i.e., those which are more expensive or non-readily available

The sugar and energy in non-carbonated sugar-sweetened beverages: a cross-sectional study.

BACKGROUND: The consumption of non-carbonated sugar-sweetened beverages (NCSSBs) has many adverse health effects. However, the sugar and energy content in NCSSBs sold in China remain unknown. We aimed to investigate the sugar and energy content of NCSSBs in China and how these contents were labelled. METHODS: A cross-sectional survey was conducted in 15 supermarkets in Haidian District, Beijing from July to October 2017. The product packaging and nutrient information panels of NCSSBs were recorded to obtain type of products (local/imported), serving size, nutrient contents of carbohydrate, sugar and energy. For those NCSSBs without sugar content information, we used carbohydrate content as a replacement. RESULTS: A total of 463 NCSSBs met the inclusion criteria and were included in our analysis. The median of sugar content and energy content was 9.6 [interquartile range (IQR): 7.1-11.3] g/100 ml and 176 (IQR: 121-201) kJ/100 ml. The median of sugar contents in juice drinks, tea-based beverages, sports drinks and energy drinks were 10.4, 8.5, 5.0 and 7.4 g/100 ml. Imported products had higher sugar and energy content than local products. There were 95.2% products of NCSSBs receiving a 'red'(high) label for sugars per portion according to the UK criteria, and 81.6% products exceeding the daily free sugar intake recommendation from the World Health Organization (25 g). There were 82 (17.7%) products with sugar content on the nutrition labels and 60.2% of them were imported products. CONCLUSIONS: NCSSBs had high sugar and energy content, and few of them provided sugar content information on their nutrition labels especially in local products. Measures including developing better regulation of labelling, reducing sugar content and restricting the serving size are needed for reducing sugar intakes in China

ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients

Determination of the Lactate Threshold by Respiratory Gas Exchange Measures and Blood Lactate Levels During Incremental-Load Work

The purpose of this investigation was to examine the change in pulmonary ventilation (V_E), ventilatory equivalent of oxygen (VE_O_2) and lactic acid (LA) in relation to oxygen uptake (V_O_2) as predictors of the lactate threshold (LT). Eight healthy male (21.9 ± 3.0 years) subjects conducted three incremental-load tests. In each test the initial work rate consisted of 4 minutes of unloaded pedaling ("0" load) followed by incremental-load work of 360 Kgm • min^-1 at 60 rpm for trial I and trial II, while during trial III the work rate consisted of 540 Kgm • min^-1 of incremental-load work at 90 rpm. Work load was increased every third minute until the subject reached voluntary exhaustion. Blood samples from a forearm vein were collected during trial II (60 rpm) and trial III (90 rpm) and analyzed for lactic acid. In our subjects the measured (x̄ ± SD) lowest VE_O_2 for O_2 in relation to V_O_2 for trial I of 22.9 ± 1.9 occurred at a V_O_2 of 1.27 ± 0.8 L • min^-1. For trial II the VE_O_2 of 22.4 ± 1.3 occurred at a V_O_2 of 1.30 ± 0.09 L • min^-1, while for trial III a VE_O_2 of 24.4 ± 2.5 occurred at a V_O_2 of 1.84 ± 0.15 L • min^-1. The lowest VE_O_2 and onset of LA accumulation as calculated from individual exponential equations relating V_E to V_O_2 yielded V_O_2 values at 1.77 ± 0.18 L • min^-1 and 1.74 ± 0.25 L • min^-1 for trial II, and 1.83 ± 0.19 L • min^-1 and 2.02 ± 0.53 during trial III. Utilizing ln[LA]-ln V_O_2 equations, the LT occurred at a V_O_2 of 1.30 ± 0.07 L • min^-1 during trial II and 1.85 ± 0.12 L • min^-1 during trial III. It was concluded that during the 60 rpm test that the lactate threshold was best predicted by measured lowest VE_O_2 and the plot of the In[LA] to In V_O_2 relationship. The methods used in this study provide a valid and reliable estimate of the lactate threshold and support the use of measured lowest VE_O_2 , a respiratory gas exchange measure, as an indirect measure of the lactate threshold