Biomedical subjects

B Drust

Publications and source records attributed to B Drust.

11 recordsLinked to original sources

PubMed2005

Testing soccer players.

To cope with the physiological demands of soccer, players must be competent across several fitness components. The use of fitness tests in the laboratory and field assist in examining soccer players' capabilities for performance both at the amateur and elite levels. Laboratory tests provide a useful indication of players' general fitness. Accurate test results can be obtained with the use of a thorough methodology and reliable equipment. Laboratory tests are used sparingly during the season because of the time-consuming nature of the tests. Instead, tests are generally carried out at the start and end of the pre-season period to evaluate the effectiveness of specific training interventions. Field tests provide results that are specific to the sport and are therefore more valid than laboratory tests. The reduced cost, use of minimal equipment and the ease with which tests can be conducted make them more convenient for extensive use throughout the season. Although data from laboratory and field tests provide a good indication of general and soccer-specific fitness, individual test results cannot be used to predict performance in match-play conclusively because of the complex nature of performance in competition. Fitness tests in conjunction with physiological data should be used for monitoring changes in players' fitness and for guiding their training prescription.

Acceleration↗

PubMed2005

The influence of pre-warming on the physiological responses to prolonged intermittent exercise.

To examine the influence of pre-warming on the physiological responses to prolonged intermittent exercise in ambient temperatures of 21.5 +/- 0.6 degrees C and relative humidities of 35.7 +/- 5.4% (mean +/- s), six healthy men performed intermittent treadmill running (30-s bouts at 90% of maximal oxygen uptake separated by 30-s static recovery periods) to exhaustion after active pre-warming, passive pre-warming and pre-exercise rest (control). Exercise time to exhaustion was significantly different between all conditions (active, 51.8 +/- 7.2 min; passive, 38.5 +/- 11.1 min; control, 72.0 +/- 17.2 min; P < 0.05). These changes in performance time were closely associated with a significant decline in both the rate of heat storage and heat storage capacity (P < 0.05). Rectal temperature, heart rate and ratings of perceived exertion were significantly higher during exercise in the two pre-warming conditions than in the control condition (P < 0.05). Ratings of perceived exertion were also significantly higher during exercise following passive pre-warming compared with active pre-warming (P < 0.05). During exercise there were no significant differences in serum prolactin, plasma norepinephrine and plasma free fatty acid concentrations between conditions. We conclude that both active and passive pre-warming promote a reduction in prolonged intermittent exercise capacity in environmental temperatures of 21 degrees C compared with pre-exercise rest. These performance decrements were dependent upon the mode of pre-warming and closely reflected alterations in body heat content.

Adult↗

PubMed2005

Circadian rhythms in sports performance--an update.

We discuss current knowledge on the description, impact, and underlying causes of circadian rhythmicity in sports performance. We argue that there is a wealth of information from both applied and experimental work, which, when considered together, suggests that sports performance is affected by time of day in normal entrained conditions and that the variation has at least some input from endogenous mechanisms. Nevertheless, precise information on the relative importance of endogenous and exogenous factors is lacking. No single study can answer both the applied and basic research questions that are relevant to this topic, but an appropriate mixture of real-world research on rhythm disturbances and tightly controlled experiments involving forced desynchronization protocols is needed. Important issues, which should be considered by any chronobiologist interested in sports and exercise, include how representative the study sample and the selected performance tests are, test-retest reliability, as well as overall design of the experiment.

Behavior↗

PubMed2005

Elevations in core and muscle temperature impairs repeated sprint performance.

AIM: The present study investigated the effects of hyperthermia on intermittent exercise and repeated sprint performance. METHODS: Seven men completed 40 min of intermittent cycling comprising of 15 s exercise (306 +/- 22 W) and 15 s rest periods (0 W) followed by 5 x 15 s maximal sprints on a cycle ergometer in normal (approximately 20 degrees C, control) and hot (40 degrees C, hyperthermia) environments. RESULTS: Completion of the intermittent protocol in the heat elevated core and muscle temperatures (39.5 +/- 0.2 degrees C; 40.2 +/- 0.4 degrees C), heart rate (178 +/- 11 beats min(-1)), rating of perceived exertion (RPE) (18 +/- 1) and noradrenaline (38.9 +/- 13.2 micromol l(-1)) (all P < 0.05). During the first sprint (n = 6), both peak and mean power output were similar across the environmental conditions. However, mean power over the last four sprints declined to a larger extent during hyperthermia compared with the control trial (P < 0.05). Consequently, average mean power output during the five sprints was lower in hyperthermia (558.0 +/- 146.9 W) compared with control (617.5 +/- 122.6 W; P < 0.05). Power output during the repeated sprints was reduced by hyperthermia despite an elevated muscle temperature that should promote sprint performance. Venous plasma potassium concentrations (H; 5.3 +/- 0.8 mmol l(-1) vs. C; 6.3 +/- 1.0 mmol l(-1), P = 0.06) and muscle lactate levels (H; 76.6 +/- 24.3 mmol kg(-1) dry weight vs. C; 108.8 +/- 20.1 mmol kg(-1) dry weight) were lower following the hyperthermic sprints compared to control. CONCLUSION: Although an elevated muscle temperature is expected to promote sprint performance, power output during the repeated sprints was reduced by hyperthermia. The impaired performance does not seem to relate to the accumulation of recognized metabolic fatigue agents and we, therefore, suggest that it may relate to the influence of high core temperature on the function of the central nervous system.

Adult↗

PubMed2005

Strategies for hydration and energy provision during soccer-specific exercise.

The aim of the present study was to investigate the effect of manipulating the provision of sports drink during soccer-specific exercise on metabolism and performance. Soccer players (N = 12) performed a soccer-specific protocol on three occasions. On two, 7 mL/kg carbohydrate-electrolyte (CHOv) or placebo (PLA) solutions were ingested at 0 and 45 min. On a third, the same total volume of carbohydrate-electrolyte was consumed (CHOf) in smaller volumes at 0, 15, 30, 45, 60, and 75 min. Plasma glucose, glycerol, non-esterified free fatty acids (NEFA), cortisol, and CHO oxidation were not significantly different between CHOv and CHOf (P > 0.05). Sprint power was not significantly affected (P > 0.05) by the experimental trials. This study demonstrates when the total volume of carbohydrate consumed is equal, manipulating the timing and volume of ingestion elicits similar metabolic responses without affecting exercise performance.

Adult↗

PubMed2003

The effects of massage on intra muscular temperature in the vastus lateralis in humans.

The aim of the current investigation was to evaluate the effect of different durations of massage, and ultrasound treatment, on the temperature of the vastus lateralis muscle in males. Deep effleurage massage of the vastus lateralis was performed on seven healthy males (mean +/- SD; age; 28 +/- 4 years, height 1.84 +/- 0.05 m, body mass 85.7 +/- 12 kg) for 5, 10 and 15 min periods. A 5-min period of ultrasound at 45 KHz was also completed by all subjects. Intra muscular temperature (at 1.5, 2.5 and 3.5 cm) and thigh skin temperature were assessed pre and post treatment. Heart rate was monitored continuously throughout all conditions. Pre treatment intra muscular temperature increased as depth of measurement increased (p = 0.00002). Changes in muscle temperature at 1.5 and 2.5 cm were significantly greater following massage than ultrasound (p < 0.002). No significant differences between massage treatments and ultrasound were noted when intra muscular temperature was measured at 3.5 cm (p > 0.05). Massage also significantly increased both heart rate and thigh skin temperature compared to ultrasound (p < 0.005). Increases in intra muscular temperature, heart rate and thigh skin temperature were the same irrespective of massage duration. These data suggest that massage and ultrasound have only limited effects on deep muscle temperature. As a result such approaches may not be suitable as a preparation strategy for exercise.

Adult↗

PubMed2002

The effects of pre-warming on the metabolic and thermoregulatory responses to prolonged submaximal exercise in moderate ambient temperatures.

To determine the effects of pre-warming on the human metabolic and thermoregulatory responses to prolonged steady-rate exercise in moderate ambient temperatures and relative humidities [means (SD) 21.7 (2.1) degrees C and 36.7 (5.4)%, respectively], six healthy men each ran at a steady-rate (70% maximal oxygen uptake) on a treadmill until exhausted after being actively pre-warmed (AH), passively pre-warmed (PH), and rested (Cont). Exercise time to exhaustion was significantly reduced following both AH and PH compared to Cont [AH 47.8 (14.0) min, PH 39.6 (16.0) min, Cont 62.0 (8.8) min; P<0.05]. During exercise there were no significant differences in oxygen uptake, total sweat loss, mean skin temperature (T(sk)) and the thermal gradient ( T(re)-T(sk), where T(re) is rectal temperature) following the three conditions. Serum prolactin, plasma catecholamine and plasma free fatty acid concentrations were also similar between all three trials. In contrast, T(re), mean body temperature, heart rate and ratings of perceived exertion were significantly greater during the initial 25 min of exercise following both AH and PH, compared with Cont ( P<0.05). At exhaustion, there were no significant differences in the metabolic and thermoregulatory responses to exercise between the trials. The current findings demonstrate that AH and PH promote a reduction in prolonged submaximal endurance performance under moderate environmental temperatures compared with pre-exercise rest. Such observations appear likely to have been mediated through mechanisms associated with the earlier development of high internal body temperature which resulted in changes in the capacity for heat storage.

Adult↗

PubMed2000

Investigation of the effects of the pre-cooling on the physiological responses to soccer-specific intermittent exercise.

Whole-body cooling prior to activity has the potential to reduce thermal strain and fatigue during subsequent endurance exercise. Intermittent activity is associated with greater increases in rectal temperature compared with continuous exercise. Thus, the effect of pre-cooling on thermoregulatory responses was examined during an intermittent test under "normal" environmental conditions. Six male university soccer players [mean (SD) age 27 (2) years; height 1.77 (0.3) m; mass 72.2 (1.5) kg; maximal oxygen consumption 58.9 (3.5) ml x kg(-1) x min(-1)] completed a 90-minute soccer-specific intermittent exercise protocol on a non-motorized treadmill. The run was completed with and without pre-cooling under normal laboratory conditions (20 degrees C) and without pre-cooling in a heated laboratory (26 degrees C). The pre-cooling strategy involved exposure to a cold shower (26 degrees C) for 60 min. The pre-cooling manipulation lowered rectal temperature prior to exercise [-0.6 (0.6) degrees C, range -1.5 degrees C; P < 0.05]. The rectal temperature response to exercise was significantly lower following pre-cooling than in the heated condition [pre-cooled 38.1 (0.6) degrees C, heated 38.6 (0.3) degrees C]. The increase in rectal temperature during the second half of the protocol following pre-cooling was significantly greater than the increase observed under normal or heated conditions (P < 0.05). No significant differences were observed between the three conditions for oxygen consumption, heart rate, minute ventilation, rating of perceived exertion and plasma lactate, glucose or free fatty acid concentrations. Based on the current investigation, it can be concluded that there is no evidence for the beneficial effects of pre-cooling on the physiological responses to soccer-specific intermittent exercise under normal environmental conditions.

Adult↗

PubMed2000

Physiological responses to laboratory-based soccer-specific intermittent and continuous exercise.

The aim of this study was to devise a laboratory-based protocol for a motorized treadmill that was representative of work rates observed during soccer match-play. Selected physiological responses to this soccer-specific intermittent exercise protocol were then compared with steady-rate exercise performed at the same average speed. Seven male university soccer players (mean +/- s: age 24 +/- 2 years, height 1.78 +/- 0.1 m, mass 72.2 +/- 5.0 kg, VO2max 57.8 +/- 4 ml x kg(-1) x min(-1)) completed a 45-min soccer-specific intermittent exercise protocol on a motorized treadmill. They also completed a continuous steady-rate exercise session for an identical period at the same average speed. The physiological responses to the laboratory-based soccer-specific protocol were similar to values previously observed for soccer match-play (oxygen consumption approximately 68% of maximum, heart rate 168 +/- 10 beats x min(-1)). No significant differences were observed in oxygen consumption, heart rate, rectal temperature or sweat production rate between the two conditions. Average minute ventilation was greater (P < 0.05) in intermittent exercise (81.3 +/- 0.2 l x min(-1)) than steady-rate exercise (72.4 +/- 11.4 l x min(-1)). The rating of perceived exertion for the session as a whole was 15 +/- 2 during soccer-specific intermittent exercise and 12 +/- 1 for continuous exercise (P < 0.05). The physiological strain associated with the laboratory-based soccer-specific intermittent protocol was similar to that associated with 45 min of soccer match-play, based on the variables measured, indicating the relevance of the simulation as a model of match-play work rates. Soccer-specific intermittent exercise did not increase the demands placed on the aerobic energy systems compared to continuous exercise performed at the same average speed, although the results indicate that anaerobic energy provision is more important during intermittent than during continuous exercise at the same average speed.

Adult↗

PubMed2000

Investigation of anthropometric and work-rate profiles of elite South American international soccer players.

BACKGROUND: The aim of the current investigation was to determine the movement profiles of elite South American soccer players during international competition and examine the relationship between anthropometric profile and work-rate variables. METHODS: Seventeen full-time professional soccer players were filmed while competing for their countries. Anthropometric profiles were obtained for eleven of these players. Six full-time professional players from the English Premier League were also filmed for comparative purposes. RESULTS: The South American international players covered significantly less (p<0.05) total distance during match-play than English Premier League players (International, 8638+/-1158 m; English Premier League, 10104+/-703 m). The total distance covered during the second half of the game was significantly reduced (p<0.05) compared to the first half distance for both groups of players (mean+/-SD first half 4605+/-625 m; mean+/-SD second half 4415+/-634 m). The data for both groups of players were combined to evaluate positional differences in the workrate profile. Midfield players covered a significantly greater (p<0.05) distance than forward players (midfield, 9826+/-1031 m; forwards, 7736+/-929 m) and defenders covered a greater (p<0.05) distance jogging backwards than forward players (defenders, 276+/-155 m; forwards, 68+/-25 m). Forwards sprinted a greater distance (p<0.05) than defensive players (defenders, 231+/-142 m; forwards, 557+/-142 m). Mean somatotype was a balanced mesomorph (2-5 1/2-2). Body mass and muscle mass was related to the total distance covered (r=0.43, r=0.53, p<0.05). CONCLUSIONS: Based on these data, it seems that an individual's work-rate profile is dependent upon the type of competition and the playing position. Relationships between anthropometric profile and work-rate are complex due to the interaction between the variables that determine work-rate.

Adult↗

PubMedDate not supplied

Some chronobiological considerations related to physical exercise.

Variables associated with physical activity show circadian rhythms in resting subjects; these rhythms have both exogenous (due to the individual's lifestyle and environment) and endogenous (due to the "body clock") components. During exercise, many of the rhythms persist, even though some show decreasing amplitude with increasing severity of exercise. Whilst the value of physical fitness is not disputed (for elite athletes, for individuals who just want to be physically fit, or for patients undertaking physical rehabilitation regimens), there are certain times of the day when special care is needed. These times are soon after waking--when there is the possibility of an increased risk of cardiovascular morbidity and damage to the spine--and late in the day--when there is an increased risk of respiratory difficulties. Since physical exercise is inextricably linked with thermoregulation, there are special considerations to bear in mind when exercise takes place in cold or hot environments. Further, due to the effects of the body clock, exercise and activity during night work and after time-zone transitions presents problems peculiar to these circumstances. In addition, the menstrual cycle affects physical performance, and these circatrigintan rhythms interact with the circadian ones. Bearing in mind these factors, advice that is based upon knowledge of circadian and circatrigintan rhythms can be given to all those contemplating physical activity. Chronobiologically, there is advantage in undertaking physical activity programmes towards the middle of the waking day and not at times when a sleep or nap has just been taken.

Chronobiology Phenomena↗