The effects of warm-up on intermittent sprint performance in a hot and humid environment.

It is unknown whether a passive warm-up or an active warm-up performed at an intensity based on lactate thresholds could improve prolonged intermittent-sprint performance either in thermoneutral or hot environmental conditions. To investigate this issue, 11 male athletes performed three trials that consisted of 80 min of intermittent-sprinting performed on a cycle ergometer, preceded by either an active or a passive warm-up. Active warm-up and intermittent-sprint performance were performed in both hot and thermoneutral environmental conditions, while passive warm-up and intermittent-sprint performance were performed in hot conditions only. First sprint performance was also assessed. Results showed no significant interaction effects between any of the trials for total work (J · kg(-1)), work decrement, and power decrement (P = 0.10, P = 0.42, P = 0.10, respectively). While there were no significant differences between trials for work done for first sprint performance (P = 0.22), peak power was significantly higher after passive warm-up compared with active warm-up performed in either thermoneutral (P = 0.03) or in hot conditions (P = 0.02). Results suggest that the main benefits of warm-up for first sprint performance are derived from temperature-related effects. Active warm-up did not impair prolonged intermittent-sprint performance in the heat compared with thermoneutral conditions.

The effect of warm-up on intermittent sprint performance and selected thermoregulatory parameters.

OBJECTIVES: To investigate the effect of various warm-up intensities based upon individual lactate thresholds on subsequent intermittent sprint performance, as well as to determine which temperature (muscle; T(mu), rectal; T(re) or body; T(b)) best correlated with performance (total work, work and power output of the first sprint, and % work decrement). DESIGN: Nine male team-sport participants performed five 10-min warm-up protocols consisting of different exercise intensities on five separate occasions, separated by a week. METHODS: Each warm-up protocol was followed by a 6×4-s intermittent sprint test performed on a cycle ergometer with 21-s of recovery between sprints. T(mu), T(re) and T(b) were monitored throughout the test. RESULTS: There were no differences between warm-up conditions for total work (J kg⁻¹; P=0.442), first sprint work (J kg⁻¹; P=0.769), power output of the first sprint (W kg⁻¹; P=0.189), or % work decrement (P=0.136), respectively. Moderate to large effect sizes (>0.5; Cohen's d) suggested a tendency for improvement in every performance variable assessed following a warm-up performed at an intensity midway between lactate inflection and lactate threshold. While T(mu), T(re), T(b), heart rate, ratings of perceived exertion and plasma lactate increased significantly during the exercise protocols (P<0.05), there were no significant correlations between T(mu), T(re), and T(b) assessed immediately after each warm-up condition and any performance variable assessed. CONCLUSIONS: Warm-up performed at an intensity midway between lactate inflection and lactate threshold resulted in optimal intermittent sprint performance. Significant increases in T(mu), T(re) and T(b) during the sprint test did not affect exercise performance between warm-up conditions.

The effect of warm up on single and intermittent-sprint performance.

Lack of benefit of warm up on prolonged intermittent-sprint performance has been proposed to be due to use of a pacing strategy by participants. To investigate this, twelve participants performed four cycle trials that consisted of either prolonged intermittent-sprint performance (80 min) or single-sprint performance (4 s), with or without a warm up. The first-sprint of intermittent-sprint performance was also assessed. No interaction effects (P > 0.05) were found between trials for intermittent-sprint performance for total work (J · kg(-1)), or percentage work and power decrement. Work done during the first-sprint of intermittent-sprint performance (no warm up) was less (P < 0.001) than the first-sprint of intermittent-sprint performance (warm up; effect size (ES) = 0.59) and both single-sprint trials (warm up and no warm up; ES = 0.91, 0.75, respectively). Peak power (W · kg(-1)) for single-sprint (warm up) was greater (P < 0.05) than single-sprint (no warm up), and the first-sprint of intermittent-sprint performance (warm up and no warm up). Warm up improved single-sprint performance and the first sprint of intermittent-sprint performance. Use of a pacing strategy probably resulted in similar intermittent-sprint performance between trials. These results suggest that team-sport players should perform a warm up at the start of a game or before substitution during a game.

Australian association for exercise and sports science position statement on exercise and asthma.

Asthma, a chronic inflammatory disorder of the airways is associated with variable obstruction to the airways and is provoked by many triggers including exercise. The management of asthma is primarily pharmacological, but exercise, despite causing bronchoconstriction in almost all asthmatics, is an important adjunct to treatment. With adequate control of the hyperresponsive airways obtained with inhaled corticosteroids (ICS) and inhaled beta 2 agonists (IBA), used as both a pre-exercise preventive agent and a reliever if necessary, all asthmatics should benefit from an exercise program. Some have realised this benefit with such success as to become Olympic and world champions in many sports. Exercise programs should be individually tailored, follow established guidelines and result in similar benefits to those obtained by non-asthmatics. However asthmatics must try to avoid or minimise triggers whenever possible. A specific benefit of a physical training program is that it allows asthmatics to exercise with less bronchoconstriction at the same exercise stress, although it does not abolish or reduce airway hyperresponsiveness (AHR).

Bone mass in young women is dependent on lean body mass.

Relationships between bone mineral density (BMD) and body mass, height, fat mass, and lean mass have been reported. This study examined the relationship between body size and composition on bone density in young premenopausal women. In this study, a cross-sectional design was used. Seventy-one healthy women aged between 24 and 36 yr selected to have a wide range of boy habitus (mean body mass index, 22.7+/-3.0) underwent a dual-energy X-ray absorptiometry (DXA) whole-body bone density scan (Hologic QDR 2000). Their bone density and soft tissue body composition and anthropometric parameters (skinfolds, girths, limb lengths, bone breadths, height, and body mass) were analyzed, and their body composition was assessed by underwater weighing (UWW). Bone-free lean mass (BFLM) determined by DXA was correlated with both bone mineral content (BMC) and BMD (r=0.74, p<0.001; r=0.48, p<0.001, respectively). In addition, fat-free mass (FFM) determined by UWW was correlated with BMC and BMD (r=0.80, p<0.001; r=0.48, p<0.001, respectively). Controlling for height in the model removed most of the correlations with whole-body BMD, with the exception of FFM, BFLM, and shoulder breadth (r=0.39, p<0.001; r=0.37, p<0.01; and r=0.34, p<0.01, respectively). No correlation was found between fat mass by DXA, UWW, and sum of skinfolds and BMD. These results indicate that bone mass in premenopausal women is dependent on lean body mass.

Reliability of physiological, psychological and cognitive variables in chronic fatigue syndrome and the role of graded exercise.

The objective of this study was to assess variability in symptoms and physical capabilities in chronic fatigue syndrome (CFS) participants both before and after a graded exercise intervention. Sixty-one CFS subjects participated in a 12-week randomized controlled trial of either graded exercise (n =32) or relaxation/stretching therapy (n = 29). Specific physiological, psychological and cognitive variables were assessed once weekly over a four-week period both prior to and after the intervention period. All scores were assessed for reliability using an intraclass correlation coefficient (ICC). Apart from mental and physical fatigue, baseline ICC scores for all variables assessed were moderately to highly reliable, indicating minimal variability. Baseline scores for mental and physical fatigue were of questionable reliability, indicating a fluctuating nature to these symptoms (R1 = 0.64 and 0.60, respectively). Variability in scores for mental fatigue was reduced after graded exercise to an acceptable classification (R1 = 0.76). Results from this study support a variable nature to the symptoms of mental and physical fatigue only. Consequently, in order to more accurately report the nature of mental and physical fatigue in CFS, future studies should consider using repeated-measures analysis when assessing these symptoms. Graded exercise resulted in the reclassification of scores for mental fatigue from questionable to acceptable reliability. Key PointsChronic fatigue syndrome sufferers often report a fluctuating nature to their symptoms and physical capabilities.Weekly assessment over a four-week period of psychological, physiological and cognitive variables demonstrated that only mental and physical fatigues were of questionable reliability.A 12-week graded exercise intervention resulted in the improvement of ICC scores for mental fatigue to that of acceptable reliability.

Plasma glutamine changes after high-intensity exercise in elite male swimmers.

The aim of this study was to establish the pattern and time course of plasma glutamine recovery after acute, high-intensity exercise in well-trained swimmers. In Study 1, elite male swimmers (n=8) performed 15 x 100 m swimming intervals (ITS) at 70% and 95% of maximal 100m freestyle time. Resting plasma glutaminle levels were determined on a nonexercise control day (0% ITS). Venous blood samples were obtained prior to, immediately afte;, and 30, 60, 120, and 150 mini postexercise. In Study 2, the 95% ITS was repeated in elite male swuimmers (n=8), while control subjects (n=8) did not exercise, to test for any diurnal variation in plasma glutamine levels. Venous blood samples were obtained prior to and 2, 4, 6, and 8 h postexercise. In Study 1, no change was observed in plasma glutamine following the 0% (control) and 70% ITS, but following the 95% ITS glutamine decreased significantly (p < 0.01) over the recovery period. In Study 2, plasma glutamine again decreased over the recovery period in the swimmers, but no changes were observed in the controls. It was concluded that intensive swim traininlg results in postexercise decreases in plasma glutamine levels. Because glutamine has been suggested as a marker of overtraining, a need to measure glutaminle at standard times within training programs is indicated.

Reliability of physiological, psychological, and cognitive variables in chronic fatigue syndrome.

The purpose of this study was to assess the reliability of specific physiological, psychological, and cognitive variables in 31 chronic fatigue syndrome (CFS) subjects and 31 matched control subjects. All variables were assessed weekly over a 4-week period and reliability was determined using an intraclass correlation coefficient (ICC). Results ranged from moderately to highly reliable for all variables assessed, except for mental and physical fatigue, which were of questionable reliability in both groups (ICC = 0.61 and 0.65, respectively, for the CFS group; 0.62 and 0.52 for the control group). A Pearson product-moment correlation analysis that compared exercise performance with all psychological variables assessed, demonstrated a significant relationship between exercise performance and depression (r = .41, P = .02) in week 3 only, suggesting minimal association between objective performance and psychological responses. These correlation results support a central, as opposed to a peripheral, basis to the sensation of fatigue in CFS.

Plasma glutamine responses to high-intensity exercise before and after endurance training.

Glutamine responses to strenuous interval exercise were examined before and after 6 weeks of endurance training. Glutamine measures were obtained before and after the interval exercise sessions and training in untrained males assigned to training (T; n = 10) or control (C; n = 10) groups. Before training, C and T group glutamine progressively decreased (p < 0.05) by 18% and 16%, respectively, by 150-min postinterval exercise. Over the training period C group glutamine did not change, while T group values increased (p < 0.05) by 14%. After training, glutamine again decreased (p < 0.05) by similar percentages (C = 16% and T = 15%) by 150-min postinterval exercise, but the T group recorded higher (p < 0.05) resting and postexercise glutamine concentrations than the C group. Training induced increases in glutamine may prevent the decline in glutamine levels following strenuous exercise falling below a threshold where immune function might be acutely compromised.

Physiological responses during a submaximal cycle test in chronic fatigue syndrome.

INTRODUCTION/PURPOSE: Numerous studies have assessed physical function in individuals suffering from chronic fatigue syndrome (CFS) but neglected to match control subjects according to current activity levels, consequently casting doubt on reported results. The purpose of this study was to include current activity levels as one criterion for matching CFS subjects with healthy control subjects in order to more accurately assess physical function in these subjects. METHODS: Thirty-one healthy control subjects were matched to CFS subjects according to age, gender, body mass, height, and current activity levels. Physiological function was assessed weekly over a 4-wk period using a submaximal cycle test. RESULTS: Comparison of absolute physiological results recorded at the end of each incremental work level of the exercise test showed that ratings of perceived effort (RPE) was the only variable that was significantly different between the two groups. Scores for RPE were significantly higher in CFS subjects for each incremental work level assessed. Conversely, results recorded on completion of the exercise test showed that the control group was capable of a greater power output than the CFS group as reflected by significantly higher scores for watts per kilogram (P < 0.0005), net lactate production (P = 0.003), oxygen uptake (mL x kg(-1) x min(-1); P < 0.0005), respiratory exchange ratio (P = 0.021), and HR values as a percentage of age predicted HR(max) (P = 0.001). End-point RPE scores were again significantly higher in the CFS group (P < 0.0005). CONCLUSION: It is proposed that the reduced exercise tolerance in CFS is due to impairment in the mechanisms that constitute effort sense and/or to avoidance behaviors that result in a reluctance by these subject to exercise to full capacity.

Independent and additive effects of energy restriction and exercise on glucose and insulin concentrations in sedentary overweight men.

BACKGROUND: Overweight and inactivity are associated with impaired glucose tolerance, reduced insulin sensitivity, and diabetes. Few controlled trials have assessed the independent and combined effects of energy restriction and exercise on the prevention of these conditions. OBJECTIVE: The objective was to evaluate the independent and additive effects of 16 wk of energy restriction and exercise on glucose and insulin concentrations. DESIGN: Sixty nonsmoking, overweight, sedentary men aged 20-50 y were randomly assigned to either maintain or restrict their energy intake (4186-6279 kJ/d). Within each of these arms, the subjects were further randomly assigned to either a light-intensity (control) or a vigorous-intensity exercise program for 30 min 3 times/wk. RESULTS: Fifty-one subjects completed the study. Maximal oxygen uptake increased ( approximately 24%; P < 0.001) with vigorous but not with light exercise. Significant weight loss was observed with energy restriction (x: 10.12 kg; 95% CI: 8.02, 12.22 kg; P < 0.001) but not with exercise. Vigorous exercise reduced fasting glucose and glucose and insulin areas under the curve (AUCs) by 13% (P = 0.01) and 20% (P = 0.02), respectively. Exercise effects were independent of weight change. Energy restriction resulted in a 40% reduction in the insulin AUC (P = 0.01). Vigorous exercise and energy restriction were additive in reducing the insulin AUC. CONCLUSIONS: Energy restriction and vigorous exercise independently and additively reduce glucose and insulin concentrations in response to an oral-glucose-tolerance test. Both of these lifestyle interventions provide a potent strategy that should be an integral part of any program to reduce the risk of impaired glucose tolerance, insulin resistance, and diabetes in overweight and sedentary persons.

Randomised controlled trial of graded exercise in chronic fatigue syndrome.

OBJECTIVE: To investigate whether 12 weeks of graded exercise with pacing would improve specific physiological, psychological and cognitive functions in people with chronic fatigue syndrome (CFS). DESIGN: Randomised controlled trial. SETTING: Human performance laboratory at the University of Western Australia. PARTICIPANTS: 61 patients aged between 16 and 74 years diagnosed with CFS. INTERVENTIONS: Either graded exercise with pacing (32 patients) or relaxation/flexibility therapy (29 patients) performed twice a day over 12 weeks. MAIN OUTCOME MEASURES: Changes in any of the physiological, psychological or cognitive variables assessed. RESULTS: Following the graded exercise intervention, scores were improved for resting systolic blood pressure (P = 0.018), work capacity (W.kg(-1)) (P = 0.019), net blood lactate production (P = 0.036), depression (P = 0.027) and performance on a modified Stroop Colour Word test (P = 0.029). Rating of perceived exertion scores, associated with an exercise test, was lower after graded exercise (P = 0.013). No such changes were observed in the relaxation/flexibility condition, which served as an attention-placebo control. CONCLUSIONS: Graded exercise was associated with improvements in physical work capacity, as well as in specific psychological and cognitive variables. Improvements may be associated with the abandonment of avoidance behaviours.

Exercise improves early functional recovery after total hip arthroplasty.

The purpose of this prospective, randomized study was to apply an 8-week customized exercise program to patients (Group E) scheduled for total hip arthroplasty, followed by a postsurgery exercise program, and show the effect on functional recovery compared with control subjects (Group C) who received no additional exercise apart from routine in-hospital physical therapy. Strength, range of motion, and physical function tests were completed by 57 patients at Week 8 and Week 1 before surgery and at Weeks 3, 12, and 24 postoperatively. No differences between the exercise and control groups were observed at baseline. By 1 week before surgery, patients in Group E had shown significant improvements for Western Ontario and McMaster Universities Osteoarthritis Index (total score, stiffness, and physical function components), and combined hip strength. Patients in Group E had improved hip flexion range of motion in the diseased hip compared with patients in Group C. Significant differences in outcome measures between Group E and Group C were observed throughout the postoperative phase from Weeks 3 to 24. The current study showed that customized perioperative exercise programs are well tolerated by patients with end-stage hip arthritis, and are effective in improving early recovery of physical function after total hip arthroplasty.

The independent and combined effects of 16 weeks of vigorous exercise and energy restriction on body mass and composition in free-living overweight men--a randomized controlled trial.

This study assessed the effects of 16 weeks of energy restriction and vigorous exercise on body mass and body composition. Sixty sedentary men, mean body mass (mean +/- SD) 96.3 (13.9) kg and mean age 42.4 (5.0) years, were randomly assigned to either continue their normal energy intake or restrict energy intake by 4,186 to 6,279 kJ. d(-1). Each group was further randomized to a control light exercise program, or a vigorous exercise program for 3 half-hour sessions per week. Vigorous exercise improved maximum oxygen consumption (Vo(2max)) by approximately 24% (0.56 [95% confidence interval, 0.47 to 0.65) L. min(-1), P <.001) with no significant changes in body mass, body composition, or fat distribution. With energy restriction there was a significant reduction in body mass of 10.1 (8.0 to 12.2) kg, lean body mass (LBM) of 2.4 (1.5 to 3.3) kg, fat mass (FM) of 7.7 (5.9 to 9.6) kg, waist to hip ratio (WHR) of 0.03 (0.01 to 0.04), and the sum of 6 skinfolds of 26.9 (15.4 to 38.4) mm (P <.001). Combining vigorous exercise with energy restriction resulted in no further changes in measures of body composition. We conclude that in sedentary free-living overweight men, 16 weeks of energy restriction, but not vigorous intensity exercise, results in substantial reductions in body mass, LBM, and FM. Furthermore, vigorous intensity exercise when combined with energy restriction did not modify or enhance the changes in body fat distribution or body composition seen with energy restriction alone. The independent effects of exercise to induce changes in body mass and composition in the longer term in free-living overweight subjects on an energy-restricted diet deserve further study.