Changes in blood lactate and respiratory gas exchange measures in sports with discontinuous load profiles.
ABSTRACT This study compares two different sport events (orienteering = OTC; tennis = TEC) with discontinuous load profiles and different activity/recovery patterns by means of blood lactate (LA), heart rate (HR), and respiratory gas exchange measures (RGME) determined via a portable respiratory system. During the TEC, 20 tennis-ranked male subjects [age: 26.0 (3.7) years; height: 181.0 (5.7) cm; weight: 73.2 (6.8) kg; maximal oxygen consumption (VO(2)max): 57.3 (5.1) ml.kg(-1).min(-1)] played ten matches of 50 min. During the OTC, 11 male members of the Austrian National Team [age: 23.5 (3.9) years; height: 183.6 (6.8) cm; weight: 72.4 (3.9) kg; VO(2)max: 67.9 (3.8) ml.kg(-1).min(-1)] performed a simulated OTC (six sections; average length: 10.090 m). In both studies data from the maximal treadmill tests (TT) were used as reference values for the comparison of energy expenditure of OTC and TEC. During TEC, the average VO(2) was considerably lower [29.1 (5.6) ml(.)kg(-1.)min(-1)] or 51.1 (10.9)% of VO(2)max and 64.8.0 (13.3)% of VO(2) determined at the individual anaerobic threshold (IAT) on the TT. The short high-intensity periods (activity/recovery = 1/6) did not result in higher LA levels [average LA of games: 2.07 (0.9) mmol.l(-1)]. The highest average VO(2 )value for a whole game was 47.8 ml.kg(-1.)min(-1) and may provide a reference for energy demands required to sustain high-intensity periods of tennis predominantly via aerobic mechanism of energy delivery. During OTC, we found an average VO(2) of 56.4 (4.5) ml.kg(-1).min(-1) or 83.0 (3.8)% of VO(2)max and 94.6 (5.2)% of VO(2) at IAT. In contrast to TEC, LA were relatively high [5.16 (1.5) mmol.l(-1)) although the average VO(2) was significantly lower than VO(2) at IAT. Our data suggest that portable RGEM provides valuable information concerning the energy expenditure in sports that cannot be interpreted from LA or HR measures alone. Portable RGEM systems provide valuable assessment of under- or over-estimation of requirements of sports and assist in the optimization and interpretation of training in athletes.
Article: Air temperature and physiological and subjective responses during competitive singles tennis.[show abstract] [hide abstract]
ABSTRACT: This report describes the thermal stresses and strains during competitive singles tennis. Thermoregulatory responses were investigated during best of three set tennis matches among 25 players. A total of 86 observations were made from 43 matches played, covering each season, with ambient temperatures ranging from 14.5 to 38.4 degrees C. Core body temperature and skin temperature were recorded each minute throughout the match, whilst heart rate was logged every 15 s. Body mass and fluid intake were measured before the match, after 30 min of play and at the completion of the match to determine sweat rate. Subjective ratings of thermal strain included thermal comfort, sweatiness and perceived exertion. The thermal environment was assessed by dry bulb, wet bulb and natural wet bulb temperatures, globe temperature and wind speed. Mean (SD) core temperature after 30 min of play was 38.4 degrees C (0.4 degrees C), and demonstrated no association with air temperature or wet bulb globe temperature. Mean skin temperature was 31.8 degrees C (2.3 degrees C) ranging from 25.7 to 36.5 degrees C, and showed a positive association with air temperature (p<0.001). Heart rate varied widely during play, resulting in a mean (SD) response of 136.1 (13.7) beats/min and no association with air temperature. Sweat rate averaged 1.0 (0.4) litres/h (0.2-2.4 litres/h) or 12.8 (5.5) ml/kg/h (2.7-26.0 ml/kg/h), and demonstrated a positive relationship with air temperature (p<0.001). All subjective responses showed positive correlations with air temperature (p<0.001). Stressful environmental conditions produce a high skin temperature and rating of thermal discomfort. However, overall thermoregulatory strain during tennis is moderate, with core temperature remaining within safe levels.British journal of sports medicine 12/2007; 41(11):773-8. · 2.55 Impact Factor
Article: Match activity and physiological responses during a junior female singles tennis tournament.[show abstract] [hide abstract]
ABSTRACT: To assess physiological load in conjunction with individual patterns of match-play activity in junior female tennis players during actual singles tennis competition. Eight elite junior female tennis players (n = 8; mean (SD) age, 17.3 (1.9) years) took part in a 2 day invitational tournament. Activity pattern analysis was performed during competitive matches. Heart rate and blood lactate concentrations were measured during selected changeovers breaks in play. The activity profile of junior female players were: rally duration, (mean (SD)) 8.2 (5.2) s; rest time between rallies, 17.7 (6.5) s; effective playing time, 21.9 (3.8)%; strokes per rally, 2.7 (1.7); changes of direction per rally, 2.3 (1.4). The mean (SD) heart rate and blood lactate concentration recorded during the matches were 161 (5) beats/min and 2.0 (0.8) mmol/litre. Heart rate and blood lactate concentration values were influenced by the characteristics of the match and mean (SD) heart rate was significantly higher (p = 0.004) during service games (166 (15.4) beats/min) than in return games (156 (19.6) beats/min), while blood lactate concentrations were not significantly different (p = 0.83) between service (2.3 (0.6) mmol/litre) and return games (2.3 (0.9) mmol/litre). We found a significant (p<0.05) positive relationship between rally duration, strokes per rally, changes of direction and blood lactate and heart rate responses, with stronger correlations when the players were serving. The physiological (ie, blood lactate and heart rate) responses associated with match play were influenced by the characteristics of the match (rally duration, strokes per rally and changes of direction), with higher heart rate on service position. Training programs should reflect these demands placed on female players during competitive match play.British journal of sports medicine 11/2007; 41(11):711-6. · 2.55 Impact Factor
Article: Health benefits of tennis.[show abstract] [hide abstract]
ABSTRACT: The aim of the study was to explore the role of tennis in the promotion of health and prevention of disease. The focus was on risk factors and diseases related to a sedentary lifestyle, including low fitness levels, obesity, hyperlipidaemia, hypertension, diabetes mellitus, cardiovascular disease, and osteoporosis. A literature search was undertaken to retrieve relevant articles. Structured computer searches of PubMed, Embase, and CINAHL were undertaken, along with hand searching of key journals and reference lists to locate relevant studies published up to March 2007. These had to be cohort studies (of either cross sectional or longitudinal design), case-control studies, or experimental studies. Twenty four studies were identified that dealt with physical fitness of tennis players, including 17 on intensity of play and 16 on maximum oxygen uptake; 17 investigated the relation between tennis and (risk factors for) cardiovascular disease; and 22 examined the effect of tennis on bone health. People who choose to play tennis appear to have significant health benefits, including improved aerobic fitness, a lower body fat percentage, a more favourable lipid profile, reduced risk for developing cardiovascular disease, and improved bone health.British journal of sports medicine 12/2007; 41(11):760-8. · 2.55 Impact Factor