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89 Cerebral and muscle oxygenation responses during unilateral and bilateral quadriceps exercise in healthy females
The relationship between skeletal muscle characteristics and cycling time trial performance in middle-aged cyclists
86
B. Dascombe1*, P. Reaburn1, E. Hohman1, R. Snow2 & A. Coutts3 1 Central Queensland University 2 Deakin University 3 University of Technology, Sydney
Sunday 14 October
This study investigated the relationship between muscle histochemical and enzymatic characteristics and cycling time trial performance in competitive middle-aged road cyclists. Seven ((X ± SD) 47.9 ± 2.7 yr; 79.3 ± 12.6 kg; 3.95 ± 0.6 L·min-1) competitive male road cyclists participated in the study. Each cyclist completed an incremental test to determine anaerobic threshold and VO2max prior to completing a 30 min self-selected cycling time trial in a laboratory. Each subject underwent a resting biopsy from the v.lateralis and muscle histochemical and enzymatic characteristics were determined using standard methods. Pearson product moment correlations were used to identify relationships between 30 min time trial performance and skeletal muscle characteristics. During the 30 min time trial, an average power output of 257 ± 29 W was sustained. This corresponded to a similar exercise intensity (88.2 ± 4.0 %HRmax) to their previously-identified anaerobic threshold (84.8 ± 3.0 %HRmax). Muscle fibre composition (Type I: 58.7 ± 16.6%; Type IIa: 34.8 ± 12.9; Type IIb: 6.4 ± 4.1%) and enzyme capacities (PFK: 41.0 ± 8.3; LDH: 202.1 ± 86.1; CS; 15.3 ± 15.5: β-HAD: 1.0 ± 0.3; 2-OGDH: 0.10 ± 0.04 μmol·gprotein-1·min-1) were typical of younger endurance athletes. No significant relationships were observed between 30 min time trial power output and muscle fibre composition or aerobic enzyme activities. Mean time trial power output was inversely related to the average PFK activity of the v.lateralis (r= -0.77, p<0.05). Therefore, previously reported relationships between endurance performance and muscle characteristics may change into middle-age in competitive cyclists.
Birth date and sporting success in professional rugby league
87
K. Mummery1* & T. Hodgetts1 1 Central Queensland University, Rockhampton, QLD
Relationships between birth date and relative sporting success have been noted in numerous sports, ranging from ice hockey in North America to soccer in Europe. Generally, evidence is available that shows a relative disadvantage to players born later in the athletic year in terms of securing placement at the highest levels of competition. The purpose of the current study was to determine if there is a relationship between birth date and participation rates at the elite levels of Rugby League. Data relating to club/league membership, month of birth and nationality were collected for professional National Rugby League (NRL, Australia, n = 372) and Super League (United Kingdon, n = 273) rugby league teams. Asymmetries in birth date distribution were investigated by examining the frequencies of birthdates by quarter in the combined and league-separated samples. The results showed a significant (c2 = 25.29, p < .0001) over-representation of players born during the second quarter of the year (April to June) in the total sample. Subsequent league-specific analysis showed that this over-representation was remained in the NRL sample (c2 = 34.34, p < .0001), but not in the Super League (c2 = 1.79, p = 0.61), even when adjusting for birth hemisphere of players involved. Discussion will include suggestions for reducing the relative age effect in the NRL.
88
Acute physiological responses and physical performance profiles of youth soccer players to variations in small-sided game formats S. Hill-Haas1,4*, B. Dawson2, A. Coutts3 & Greg. Rowsell4 1 University Of Western Australia & South Australia Sports Institute 2 University of Western Australia 3 University of Technology, Sydney 4 South Australia Sports Institute
Introduction The use of small-sided games (SSG’s) for technical and tactical development of soccer players is well established. However, SSG’s are increasingly used as an alternative to generic training methods for developing and/or maintaining aerobic fitness. Although there is increasing scientific evidence in favour of adopting such an approach, a better understanding of acute physiological demands (including physical performance profiles) is needed. Consequently, the aim of this study was to examine different SSG’s formats, and their effect on acute physiological responses and performance profiles in youth soccer players. Methodology Sixteen male soccer players (mean 16.2 years, range 15.6-17.9) played in 2 vs. 2, 4 vs. 4 and 6 vs. 6 formats. Game duration was 24 min. Mean heart rate (HR) as well as time spent in various HR zones was measured every 5 s using short-range radiotelemetry (Polar Team Sport System, Polar Electro, Kempele, Finland). A time-motion characteristic of every player was calculated using global positioning system (GPS) technology. Ratings of perceived exertion (RPE) and blood lactate (La-) were also recorded post game. One-way ANOVA was used to determine differences between the three playing formats. Statistical significance was set at P<0.05. Results Discussion (1) Greatest physiological load in 2 v 2 formats as evidenced by highest blood La, highest RPE and highest average HR. (2) This trend extended to less physiological load in 4 v 4 formats, and the lowest physiological load in 6 v 6 games. (3) paradoxically, the greatest physiological load did not translate to a quantitatively greater performance profile. (4) Differences between
Cerebral and muscle oxygenation responses during unilateral and bilateral quadriceps exercise in healthy females
89
Y. Bhambhani1*, C. Matsuura2 & P. Gomes2 1 University Of Alberta, Edmonton, Canada 2 Universidade Gama Filho, Rio de Janeiro, Brazil
Background: Near infrared spectroscopy (NIRS) is used to evaluate changes in cerebral and muscle oxygenation and blood volume during exercise. Increases in cerebral oxygenation are implicated in enhanced neuronal activation. Decreases in muscle oxygenation imply enhanced oxygen extraction. Purpose: To examine the relationship between knee extension performance and changes in cerebral and muscle oxygenation/blood volume in healthy females. Methods: Informed consent was obtained from nine volunteers who completed two exercise sessions. In session one, one repetition maximum (1RM) of the right (R), left (L) and both (B) legs were determined. In session two, maximum repetitions at 75% of 1 RM were determined as follows: 2 min rest, R, L and B exercise in random order, 4 min recovery between exercises. Cerebral and muscle NIRS measurements were recorded bilaterally simultaneously from the prefrontal lobes and vastus lateralis muscles. Results: During R, L and B, cerebral oxygenation/blood volume increased in both lobes while muscle oxygenation/blood volume decreased in the exercising limbs only. Significant correlations (p<.05) were observed between R absolute work (resistance x repetitions) and: cerebral oxygenation (r = 0.72), cerebral blood volume (r = 0.88). L and B absolute work were not significantly (p>.05) correlated with cerebral oxygenation and blood volume. R, L and B absolute work were not significantly correlated with muscle oxygenation or blood volume. Conclusions: Fatigue during resistance exercise is more closely associated with neuronal activation rather than intramuscular oxygen utilization. Neuronal activation on the ipsilateral side plays a more important role in determining resistance exercise capacity. Funding: Small Faculties Committee, University of Alberta; Capes Foundation, Brazil. 41
86
B. Dascombe1*, P. Reaburn1, E. Hohman1, R. Snow2 & A. Coutts3 1 Central Queensland University 2 Deakin University 3 University of Technology, Sydney
Sunday 14 October
This study investigated the relationship between muscle histochemical and enzymatic characteristics and cycling time trial performance in competitive middle-aged road cyclists. Seven ((X ± SD) 47.9 ± 2.7 yr; 79.3 ± 12.6 kg; 3.95 ± 0.6 L·min-1) competitive male road cyclists participated in the study. Each cyclist completed an incremental test to determine anaerobic threshold and VO2max prior to completing a 30 min self-selected cycling time trial in a laboratory. Each subject underwent a resting biopsy from the v.lateralis and muscle histochemical and enzymatic characteristics were determined using standard methods. Pearson product moment correlations were used to identify relationships between 30 min time trial performance and skeletal muscle characteristics. During the 30 min time trial, an average power output of 257 ± 29 W was sustained. This corresponded to a similar exercise intensity (88.2 ± 4.0 %HRmax) to their previously-identified anaerobic threshold (84.8 ± 3.0 %HRmax). Muscle fibre composition (Type I: 58.7 ± 16.6%; Type IIa: 34.8 ± 12.9; Type IIb: 6.4 ± 4.1%) and enzyme capacities (PFK: 41.0 ± 8.3; LDH: 202.1 ± 86.1; CS; 15.3 ± 15.5: β-HAD: 1.0 ± 0.3; 2-OGDH: 0.10 ± 0.04 μmol·gprotein-1·min-1) were typical of younger endurance athletes. No significant relationships were observed between 30 min time trial power output and muscle fibre composition or aerobic enzyme activities. Mean time trial power output was inversely related to the average PFK activity of the v.lateralis (r= -0.77, p<0.05). Therefore, previously reported relationships between endurance performance and muscle characteristics may change into middle-age in competitive cyclists.
Birth date and sporting success in professional rugby league
87
K. Mummery1* & T. Hodgetts1 1 Central Queensland University, Rockhampton, QLD
Relationships between birth date and relative sporting success have been noted in numerous sports, ranging from ice hockey in North America to soccer in Europe. Generally, evidence is available that shows a relative disadvantage to players born later in the athletic year in terms of securing placement at the highest levels of competition. The purpose of the current study was to determine if there is a relationship between birth date and participation rates at the elite levels of Rugby League. Data relating to club/league membership, month of birth and nationality were collected for professional National Rugby League (NRL, Australia, n = 372) and Super League (United Kingdon, n = 273) rugby league teams. Asymmetries in birth date distribution were investigated by examining the frequencies of birthdates by quarter in the combined and league-separated samples. The results showed a significant (c2 = 25.29, p < .0001) over-representation of players born during the second quarter of the year (April to June) in the total sample. Subsequent league-specific analysis showed that this over-representation was remained in the NRL sample (c2 = 34.34, p < .0001), but not in the Super League (c2 = 1.79, p = 0.61), even when adjusting for birth hemisphere of players involved. Discussion will include suggestions for reducing the relative age effect in the NRL.
88
Acute physiological responses and physical performance profiles of youth soccer players to variations in small-sided game formats S. Hill-Haas1,4*, B. Dawson2, A. Coutts3 & Greg. Rowsell4 1 University Of Western Australia & South Australia Sports Institute 2 University of Western Australia 3 University of Technology, Sydney 4 South Australia Sports Institute
Introduction The use of small-sided games (SSG’s) for technical and tactical development of soccer players is well established. However, SSG’s are increasingly used as an alternative to generic training methods for developing and/or maintaining aerobic fitness. Although there is increasing scientific evidence in favour of adopting such an approach, a better understanding of acute physiological demands (including physical performance profiles) is needed. Consequently, the aim of this study was to examine different SSG’s formats, and their effect on acute physiological responses and performance profiles in youth soccer players. Methodology Sixteen male soccer players (mean 16.2 years, range 15.6-17.9) played in 2 vs. 2, 4 vs. 4 and 6 vs. 6 formats. Game duration was 24 min. Mean heart rate (HR) as well as time spent in various HR zones was measured every 5 s using short-range radiotelemetry (Polar Team Sport System, Polar Electro, Kempele, Finland). A time-motion characteristic of every player was calculated using global positioning system (GPS) technology. Ratings of perceived exertion (RPE) and blood lactate (La-) were also recorded post game. One-way ANOVA was used to determine differences between the three playing formats. Statistical significance was set at P<0.05. Results Discussion (1) Greatest physiological load in 2 v 2 formats as evidenced by highest blood La, highest RPE and highest average HR. (2) This trend extended to less physiological load in 4 v 4 formats, and the lowest physiological load in 6 v 6 games. (3) paradoxically, the greatest physiological load did not translate to a quantitatively greater performance profile. (4) Differences between
Cerebral and muscle oxygenation responses during unilateral and bilateral quadriceps exercise in healthy females
89
Y. Bhambhani1*, C. Matsuura2 & P. Gomes2 1 University Of Alberta, Edmonton, Canada 2 Universidade Gama Filho, Rio de Janeiro, Brazil
Background: Near infrared spectroscopy (NIRS) is used to evaluate changes in cerebral and muscle oxygenation and blood volume during exercise. Increases in cerebral oxygenation are implicated in enhanced neuronal activation. Decreases in muscle oxygenation imply enhanced oxygen extraction. Purpose: To examine the relationship between knee extension performance and changes in cerebral and muscle oxygenation/blood volume in healthy females. Methods: Informed consent was obtained from nine volunteers who completed two exercise sessions. In session one, one repetition maximum (1RM) of the right (R), left (L) and both (B) legs were determined. In session two, maximum repetitions at 75% of 1 RM were determined as follows: 2 min rest, R, L and B exercise in random order, 4 min recovery between exercises. Cerebral and muscle NIRS measurements were recorded bilaterally simultaneously from the prefrontal lobes and vastus lateralis muscles. Results: During R, L and B, cerebral oxygenation/blood volume increased in both lobes while muscle oxygenation/blood volume decreased in the exercising limbs only. Significant correlations (p<.05) were observed between R absolute work (resistance x repetitions) and: cerebral oxygenation (r = 0.72), cerebral blood volume (r = 0.88). L and B absolute work were not significantly (p>.05) correlated with cerebral oxygenation and blood volume. R, L and B absolute work were not significantly correlated with muscle oxygenation or blood volume. Conclusions: Fatigue during resistance exercise is more closely associated with neuronal activation rather than intramuscular oxygen utilization. Neuronal activation on the ipsilateral side plays a more important role in determining resistance exercise capacity. Funding: Small Faculties Committee, University of Alberta; Capes Foundation, Brazil. 41