Influence of playing standard on the physical demands of professional rugby league

Abstract

In this paper we report on two studies that investigated the physical demands of professional rugby league match-play. Instudy one, National Rugby League (NRL) and National Youth Competition (NYC) players underwent global positioning system (GPS) analysis during competitive matches. No differences (P > 0.05) were observed between playing standards for minutes played, total distance covered, or the distances covered at low and high speeds. However, NRL players engaged in significantly more repeated high-intensity effort bouts than NYC players (13.1 ± 0.8 bouts vs. 9.7 ± 1.1 bouts). Reductions in physical performance occurred from the first to second half for both NRL and NYC players. In study two, we investigated, in the same players, the physical demands of professional rugby league match-play when players were competing in trial and regular fixture matches. The locomotor demands of trial matches were lower than fixture matches, with players covering less distance per minute of match-play, including less distance at low and high speeds. Players were also less likely to engage in repeated high-intensity effort bouts in trial matches than fixtures. These findings demonstrate that neither NYC matches nor NRL trial matches adequately reflect the intense physical demands of NRL fixture matches.     

Exercise training increases the S-Klotho plasma levels in sedentary middle-aged adults: A randomised controlled trial. The FIT-AGEING study

ABSTRACT

This study aimed to investigate the effects of different training modalities on the soluble Klotho (S-Klotho) plasma levels in sedentary middle-aged adults. A total of 74 middle-aged adults (53.4 ± 5.0 years old; 52.7% women) were enrolled in the FIT-AGEING study. We conducted a 12-week randomised controlled trial. The participants were randomly assigned to 4 different groups: (i) a control group (no exercise), (ii) a physical activity recommendation from the World Health Organization group (PAR), (iii) a high intensity interval training group (HIIT), and (iv) a high intensity interval training group adding whole-body electromyostimulation training group (HIIT-EMS). S-Klotho plasma levels, anthropometric measurements, and body composition variables were measured before and after the intervention programme. All exercise training modalities induced an increase in the S-Klotho plasma levels (all P ≤ 0.019) without statistical differences between them (all P ≥ 0.696). We found a positive association between changes in lean mass index and changes in the S-Klotho plasma levels, whereas a negative association was reported between changes in fat mass outcomes and changes in the S-Klotho plasma levels after our intervention study. In conclusion, our results suggest that the link between exercise training and the increase in S-Klotho plasma levels could be mediated by a decrease of fat mass and an increase of lean mass.     

Bone mineral density and lean mass asymmetries are greater in cyclists than non-cyclists

ABSTRACT

Cyclists may be at greater risk of developing asymmetrical force and motion patterns than other ground-based athletes. However, functional asymmetries during cycling tend to be highly variable, making them difficult to assess. Dual-energy x-ray absorptiometry (DXA) measurements of areal bone mineral density (aBMD) and lean mass (LM) in the lower limbs may be a more sensitive and consistent method to identify asymmetries in cyclists. The goal of this study was to determine if competitive cyclists have greater levels of asymmetries in the lower body compared to non-cyclists using DXA. A secondary aim was to determine if aBMD and LM asymmetries change over the road cycling season. 17 competitive cyclists and 21 non-cyclist, healthy controls underwent DXA scans. Lower-body asymmetries were greater in cyclists compared to non-cyclists in aBMD and LM for all lower limb segments. However, these asymmetries did not tend to consistently favour a particular side, except for the pelvis having more LM on the dominant side. The were no longitudinal changes in aBMD or LM in the cyclists. Asymmetry analysis via DXA provides evidence that although functional asymmetries during cycling are variable, cyclists have increased lower body LM and aBMD asymmetries compared to non-cyclists.     

Nutritional strategies for promoting fat utilization and delaying the onset of fatigue during prolonged exercise

Carbohydrate ingestion before and during endurance exercise delays the onset of fatigue (reduced power output). Therefore, endurance athletes are recommended to ingest diets high in carbohydrate (70% of total energy) during competition and training. However, increasing the availability of plasma free fatty acids has been shown to slow the rate of muscle and liver glycogen depletion by promoting the utilization of fat. Ingested fat, in the form of long-chain (C 16-22 ) triacylglycerols, is largely unavailable during acute exercise, but medium-chain (C 8-10 ) triacylglycerols are rapidly absorbed and oxidized. We have shown that the ingestion of medium-chain triacylglycerols in combination with carbohydrate spares muscle carbohydrate stores during 2 h of submaximal (< 70% VO 2 peak) cycling exercise, and improves 40 km time-trial performance. These data suggest that by combining carbohydrate and medium-chain triacylglycerols as a pre-exercise supplement and as a nutritional supplement during exercise, fat oxidation will be enhanced, and endogenous carbohydrate will be spared. We have also examined the chronic metabolic adaptations and effects on substrate utilization and endurance performance when athletes ingest a diet that is high in fat (> 70% by energy). Dietary fat adaptation for a period of at least 2-4 weeks has resulted in a nearly two-fold increase in resistance to fatigue during prolonged, low- to moderate-intensity cycling (< 70% VO 2 peak). Moreover, preliminary studies suggest that mean cycling 20 km time-trial performance following prolonged submaximal exercise is enhanced by 80 s after dietary fat adaptation and 3 days of carbohydrate loading. Thus the relative contribution of fuel substrate to prolonged endurance activity may be modified by training, pre-exercise feeding, habitual diet, or by artificially altering the hormonal milieu or the availability of circulating fuels. The time course and dose-response of these effects on maximizing the oxidative contribution of fat for exercise metabolism and in exercise performance have not been systematically studied during moderate- to high-intensity exercise in humans.     

The influence of intermittent high-intensity shuttle running and fluid ingestion on the performance of a soccer skill

The aim of this study was to examine the effect of intermittent high-intensity shuttle running and fluid ingestion on the performance of a soccer skill. Nine semi-professional soccer players volunteered to participate in the study. Their mean (± _sx ) age, body mass and maximal oxygen uptake were 20.2 ± 0.4 years, 73.2 ± 1.8 kg and 59.1 ± 1.3 ml·kg^-1 ·min^-1 respectively. The players were allocated to two randomly assigned trials: ingesting or abstaining from fluid intake during a 90 min intermittent exercise protocol (Loughborough Intermittent Shuttle Test:LIST).This test was designed to simulate the minimum physical demands faced by soccer players during a game. Before and immediately after performance of the test,the players completed a soccer skill test and a mental concentration test. Performance of the soccer skill test after the 'no-fluid' trial deteriorated by 5% (P ? 0.05),but was maintained during the fluid trial. Mean heart rate, perceived exertion, serum aldosterone, osmolality, sodium and cortisol responses during the test were higher (P ? 0.05) in the 'no-fluid' trial than in the fluid trial. The results of this study suggest that soccer players should consume fluid throughout a game to help prevent a deterioration in skill performance.     

Matching of Male and Female Subjects Using VO2 max

Abstract

We compared cardiorespiratory responses to exercise on an underwater treadmill (UTM) and land treadmill (LTM) and derived an equation to estimate oxygen consumption (VO₂) during UTM exercise. Fifty-five men and women completed one LTM and five UTM exercise sessions on separate days. The UTM sessions consisted of chest-deep immersion, with 0, 25, 50, 75, and 100% water-jet resistance. All session treadmill velocities increased every 3 min from 53.6 to 187.8 m·min^-1. Cardiorespiratory responses were similar between LTM and UTM when jet resistance for UTM was ≥ 50%. Using multiple regression analysis, weight-relative VO₂ could be estimated as: VO₂ (mLO₂·kg^-1·min^-1) = 0.19248 · height (cm) + 0.17422 · jet resistance (% max) + 0.14092 · velocity (m·min^-1) - 0.12794 · weight (kg) - 27.82849, R²= .82. Our data indicate that similar LTM and UTM cardiorespiratory responses are achievable, and we provide a reasonable estimate of UTM VO₂.     

Responses to Forces Influencing Cohesion As a Function of Player Status and Level of Male Varsity Basketball Competition

Abstract

This exploratory study determined if the responses of male varsity basketball players to six factors influencing cohesion were a function of level of competitive intensity and/or the importance of the players to their team. Players on intact teams from five levels of competition – elementary school, junior high school, senior high school, small college and large college–responded to a cohesion questionnaire at the end of the season. Coaches designated five players with the most game playing time as “starters” and five players with the least game playing time as “reserves.” A team factor score for Team Performance Satisfaction, Self Performance Satisfaction, Task Cohesion, Affiliation Cohesion, Desire for Recognition and Value of Membership was calculated. Each team factor score served as the dependent variable in a 2 (player status) × 5 (level of competition) analysis ofcovariance design, with teams nested in the second factor. The won-loss record served as the covariate. Results indicated that “starters” were more satisfied with their own performance, were more task conscious, had a greater affiliation desire, and valued their membership on the team to a greater degree than the “reserves.” The elementary and junior high school team members were significantly more satisfied with the team's performance, were more satisfied with their own self performance, were more affiliation conscious, and valued their team membership to a greater degree than did college team members. The interaction between player status and level of competition was not significant for any of the factor scores.     

The Effects of a Group Contingency Strategy on Behaviorally Disordered Students in Physical Education

Abstract

An A-B-A-B time-series design was used to determine the effectiveness of a group contingency strategy in modifying on-task behavior of behaviorally disordered students in a physical education setting. A younger group (n = 12) with a mean age of 7.8 years, and an older group (n = 11) with a mean age of 11.2 years, participated in a study in which activity reinforcement for each group was contingent upon correct observation of the rules established for class. The group contingency strategy was significantly effective in increasing the percentage of on-task behavior of both groups of students. In addition, there was no significant difference in the response to treatment between younger and older students, and there were no individuals within either group who did not respond favorably to treatment.     

Prolonged static stretching does not influence running economy despite changes in neuromuscular function

The aim of this study was to examine the acute effects of prolonged static stretching (SS) on running economy. Ten male runners (VO2(peak) 60.1 +/- 7.3 ml x kg(-1) x min(-1)) performed 10 min of treadmill running at 70% VO2(peak) before and after SS and no stretching interventions. For the stretching intervention, each leg was stretched unilaterally for 40 s with each of eight different exercises and this was repeated three times. Respiratory gas exchange was measured throughout the running exercise with an automated gas analysis system. On a separate day, participants were tested for sit and reach range of motion, isometric strength and countermovement jump height before and after SS. The oxygen uptake, minute ventilation, energy expenditure, respiratory exchange ratio and heart rate responses to running were unaffected by the stretching intervention. This was despite a significant effect of SS on neuromuscular function (sit and reach range of motion, +2.7 +/- 0.6 cm; isometric strength, -5.6% +/- 3.4%; countermovement jump height -5.5% +/- 3.4%; all P < 0.05). The results suggest that prolonged SS does not influence running economy despite changes in neuromuscular function.     

Student Perceptions of Chemistry Laboratory Learning Environments, Student–Teacher Interactions and Attitudes in Secondary School Gifted Education Classes in Singapore

This study investigated the chemistry laboratory classroom environment, teacher–student interactions and student attitudes towards chemistry among 497 gifted and non-gifted secondary-school students in Singapore. The data were collected using the 35-item Chemistry Laboratory Environment Inventory (CLEI), the 48-item Questionnaire on Teacher Interaction (QTI) and the 30-item Questionnaire on Chemistry-Related Attitudes (QOCRA). Results supported the validity and reliability of the CLEI and QTI for this sample. Stream (gifted versus non-gifted) and gender differences were found in actual and preferred chemistry laboratory classroom environments and teacher–student interactions. Some statistically significant associations of modest magnitude were found between students' attitudes towards chemistry and both the laboratory classroom environment and the interpersonal behaviour of chemistry teachers. Suggestions for improving chemistry laboratory classroom environments and the teacher–student interactions for gifted students are provided.