Changes in muscle recruitment, functional strength and ratings of perceived effort during an 8-over bowling spell: impact on performance
- Authors: Barford, Gareth Charles
- Date: 2013
- Subjects: Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5102 , http://hdl.handle.net/10962/d1003926 , Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Description: Background: The musculoskeletal demands placed on the lower limb musculature of fast bowlers over time have not received much attention. In particular, measures of muscle recruitment changes have, to the author’s knowledge, not been considered. Objective: The present study, therefore sought to establish any associations between an eight over, simulated fast bowling spell, and muscle activation patterns, power output, perceptual demands, and changes in performance. This will enable improvements in the development of training programmes. Methods: Players’ were required to attend two sessions in total. The purpose of the initial session was to collect specific demographic, anthropometric and physiological data and injury history information from each player. In addition, this first session allowed for habituation with the treadmill, the jump meter and all other equipment involved in experimentation. The second testing session involved electrode attachment sites being identified on player’s dominant leg. The areas were then shaved, wiped with an alcohol swab and left to dry, to ensure good connectivity. Pre- and post- measures of muscle activity and functional strength of the lower limbs were recorded in the Department of Human Kinetics and Ergonomics. The protocol took place at the Kingswood High Performance Centre, which is in close proximity to the initial testing site. The protocol involved players bowling eight overs (48 balls). During the protocol, accuracy, ball release speed and perceptual measures were recorded at the end of each over. After the protocol, players were driven back to the Human Kinetics and Ergonomics Department where post-testing measures were completed. The dependable variables of interest were muscle activation, functional strength of the lower limbs, ‘local’ ratings of perceived exertion (RPE), body discomfort, accuracy, and ball release speed. Results: For all muscles it was shown that, as the speed increased so did the muscle activity in players’ lower limbs. There were no significant changes in muscle activity preversus post-protocol. There was however, a general trend of decreasing muscle activity post protocol at higher testing speeds. There were significant (p<0.05) decreases in peak power following the simulated eight over bowling spell. ‘Local’ RPE displayed a significant (P<0.05) increase with each additional over and were observed to reach the ‘heavy’ category. The players’ highest discomfort area was in the lower back, with 13 players perceiving discomfort in this region following the eight over spell. The shoulder and chest were another two areas player’s indicated discomfort with eight players selecting the dominant shoulder. Seven players complained of the dominant side pectoral muscle, leading foot and dominant latissimus dorsi muscle being uncomfortable. Interestingly, the dominant pectoral showed the highest body discomfort ratings amongst players. There were no significant changes in accuracy between overs although there were large interindividual differences in accuracy points between players. The decrease in ball release speed observed during over seven was shown to be significantly (p<0.05) lower than overs one to four. Conclusion: The power output and perceived strain results of the players, appears to indicate the presence of fatigue in players. However, the results are not conclusive, as the fatigue was not shown in muscle recruitment patterns, as well as the body discomfort ratings. There was a non-significant trend observed in the lower limb muscle activation decreasing at higher speeds. Players were able to maintain accuracy. However, the significantly lower ball release speed observed during over seven showed players performance decreasing.
- Full Text:
- Authors: Barford, Gareth Charles
- Date: 2013
- Subjects: Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5102 , http://hdl.handle.net/10962/d1003926 , Cricket -- Bowling , Sports -- Physiological aspects , Muscles -- Wounds and injuries , Fatigue , Physical fitness , Cricket injuries
- Description: Background: The musculoskeletal demands placed on the lower limb musculature of fast bowlers over time have not received much attention. In particular, measures of muscle recruitment changes have, to the author’s knowledge, not been considered. Objective: The present study, therefore sought to establish any associations between an eight over, simulated fast bowling spell, and muscle activation patterns, power output, perceptual demands, and changes in performance. This will enable improvements in the development of training programmes. Methods: Players’ were required to attend two sessions in total. The purpose of the initial session was to collect specific demographic, anthropometric and physiological data and injury history information from each player. In addition, this first session allowed for habituation with the treadmill, the jump meter and all other equipment involved in experimentation. The second testing session involved electrode attachment sites being identified on player’s dominant leg. The areas were then shaved, wiped with an alcohol swab and left to dry, to ensure good connectivity. Pre- and post- measures of muscle activity and functional strength of the lower limbs were recorded in the Department of Human Kinetics and Ergonomics. The protocol took place at the Kingswood High Performance Centre, which is in close proximity to the initial testing site. The protocol involved players bowling eight overs (48 balls). During the protocol, accuracy, ball release speed and perceptual measures were recorded at the end of each over. After the protocol, players were driven back to the Human Kinetics and Ergonomics Department where post-testing measures were completed. The dependable variables of interest were muscle activation, functional strength of the lower limbs, ‘local’ ratings of perceived exertion (RPE), body discomfort, accuracy, and ball release speed. Results: For all muscles it was shown that, as the speed increased so did the muscle activity in players’ lower limbs. There were no significant changes in muscle activity preversus post-protocol. There was however, a general trend of decreasing muscle activity post protocol at higher testing speeds. There were significant (p<0.05) decreases in peak power following the simulated eight over bowling spell. ‘Local’ RPE displayed a significant (P<0.05) increase with each additional over and were observed to reach the ‘heavy’ category. The players’ highest discomfort area was in the lower back, with 13 players perceiving discomfort in this region following the eight over spell. The shoulder and chest were another two areas player’s indicated discomfort with eight players selecting the dominant shoulder. Seven players complained of the dominant side pectoral muscle, leading foot and dominant latissimus dorsi muscle being uncomfortable. Interestingly, the dominant pectoral showed the highest body discomfort ratings amongst players. There were no significant changes in accuracy between overs although there were large interindividual differences in accuracy points between players. The decrease in ball release speed observed during over seven was shown to be significantly (p<0.05) lower than overs one to four. Conclusion: The power output and perceived strain results of the players, appears to indicate the presence of fatigue in players. However, the results are not conclusive, as the fatigue was not shown in muscle recruitment patterns, as well as the body discomfort ratings. There was a non-significant trend observed in the lower limb muscle activation decreasing at higher speeds. Players were able to maintain accuracy. However, the significantly lower ball release speed observed during over seven showed players performance decreasing.
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Selected physiological and perceptual responses of batsmen during a simulated one day international century : impact on performance
- Authors: Pote, Lee
- Date: 2013 , 2013-04-02
- Subjects: Cricket -- Batting , Sports -- Physiological aspects , Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5097 , http://hdl.handle.net/10962/d1001650
- Description: Background: Very few studies have examined the demands of prolonged batting on physical, psychophysical and performance responses. Objective: The purpose of this study was therefore to determine the physiological and perceptual responses of batsmen scoring a simulated One Day International century. Furthermore, the impact that these responses had on batting performance were also measured. Methods: Seventeen male cricketers currently playing for Rhodes University or the country districts side, performed a simulated bating innings (BATEX©), typical of scoring a One Day international century. The BATEX© protocol consisted of six, five over stages (21 minutes each), with each stage matched to a specific phase of play where batsmen were encouraged to bat with the mindset of that phase. During stages one, three and five players ran at a “self-selected cruise pace” whereas during stages two, four and six players were required to run at maximum speed. At set intervals, selected physiological, perceptual and performance measures were recorded. Results: Most physiological responses increased and decreased accordingly with the low and high intensity stages with the exception of respiratory exchange ratio and core temperature responses. Mean physiological responses however, showed a progressive rise over time. Central ratings of perceived exertion increased as a function of intensity and duration. Sprint times got slower as the protocol progressed, while accuracy (impact accuracy) improved significantly (p<0.05) after stage one and then stabilised for the remainder of the protocol. Conclusion: The simulated batting protocol significantly impacted the physiological and perceptual responses over time. This was due to both the intensity and the duration of the work-bout. Furthermore, the increased physiological load placed on the batsmen significantly impacted the physical performance of the batsmen. An increase in sprint times (players getting slower) towards the end of the protocol may indicate the presence of physical fatigue. This physical fatigue did not however seem to impact the batsmen cognitively as accuracy improved after the first stage and then remained constant over time.
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- Authors: Pote, Lee
- Date: 2013 , 2013-04-02
- Subjects: Cricket -- Batting , Sports -- Physiological aspects , Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5097 , http://hdl.handle.net/10962/d1001650
- Description: Background: Very few studies have examined the demands of prolonged batting on physical, psychophysical and performance responses. Objective: The purpose of this study was therefore to determine the physiological and perceptual responses of batsmen scoring a simulated One Day International century. Furthermore, the impact that these responses had on batting performance were also measured. Methods: Seventeen male cricketers currently playing for Rhodes University or the country districts side, performed a simulated bating innings (BATEX©), typical of scoring a One Day international century. The BATEX© protocol consisted of six, five over stages (21 minutes each), with each stage matched to a specific phase of play where batsmen were encouraged to bat with the mindset of that phase. During stages one, three and five players ran at a “self-selected cruise pace” whereas during stages two, four and six players were required to run at maximum speed. At set intervals, selected physiological, perceptual and performance measures were recorded. Results: Most physiological responses increased and decreased accordingly with the low and high intensity stages with the exception of respiratory exchange ratio and core temperature responses. Mean physiological responses however, showed a progressive rise over time. Central ratings of perceived exertion increased as a function of intensity and duration. Sprint times got slower as the protocol progressed, while accuracy (impact accuracy) improved significantly (p<0.05) after stage one and then stabilised for the remainder of the protocol. Conclusion: The simulated batting protocol significantly impacted the physiological and perceptual responses over time. This was due to both the intensity and the duration of the work-bout. Furthermore, the increased physiological load placed on the batsmen significantly impacted the physical performance of the batsmen. An increase in sprint times (players getting slower) towards the end of the protocol may indicate the presence of physical fatigue. This physical fatigue did not however seem to impact the batsmen cognitively as accuracy improved after the first stage and then remained constant over time.
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Time course of performance changes and fatigue markers during training for the ironman triathlon
- Authors: Joiner, Alexander Jason
- Date: 2010
- Subjects: Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5133 , http://hdl.handle.net/10962/d1005212 , Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Description:
Suboptimal preparation for the Ironman triathlon can have detrimental effects on mental and physical condition. The purpose of this longitudinal investigation was to examine the relationship between a number of performance changes and fatigue markers during training for an Ironman as well as immediately after the event, in an attempt to better understand the effects of ultraendurance training. Eighteen athletes training for the Ironman; South Africa, 2009 were recruited for the study. Over the 6 month data collection period body mass, training load (TRIMP and Session x RPE methods), physiological responses (waking heart rate, postural dizziness, sleep ratings), changes in psychological state (profile of mood states - POMS), reported immunological responses (symptoms of illness), biochemical changes (salivary cortisol and alpha amylase) and performance (8 km submaximal running time trial (TT) and race day performance) were measured. These responses were compared to a control sample (n=15). Results show a significant increase (p<0.05) in training load (3899.4 ± 2517.8) four weeks prior to the event. Fatigue scores significantly increased (p<0.05) concurrently with this significant increase (p<0.05) in training. TT performance did not significantly (p<0.05) alter during the time course of training. It was however strongly correlated to training load (R2=0.85) and modestly related to race performance (R2=0.65). The signs and symptoms of upper respiratory tract infections (URTI) were prevalent during the training period, decreasing during the taper and race period. Large standard deviations were found within the majority of the responses. During the final two weeks of preparation, tension scores were significantly increased (p<0.05) while training load significantly decreased (p<0.05) during the final week of preparation. Cortisol increased significantly (p<0.05) immediately post race (0.507±0.15
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- Authors: Joiner, Alexander Jason
- Date: 2010
- Subjects: Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5133 , http://hdl.handle.net/10962/d1005212 , Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Description:
Suboptimal preparation for the Ironman triathlon can have detrimental effects on mental and physical condition. The purpose of this longitudinal investigation was to examine the relationship between a number of performance changes and fatigue markers during training for an Ironman as well as immediately after the event, in an attempt to better understand the effects of ultraendurance training. Eighteen athletes training for the Ironman; South Africa, 2009 were recruited for the study. Over the 6 month data collection period body mass, training load (TRIMP and Session x RPE methods), physiological responses (waking heart rate, postural dizziness, sleep ratings), changes in psychological state (profile of mood states - POMS), reported immunological responses (symptoms of illness), biochemical changes (salivary cortisol and alpha amylase) and performance (8 km submaximal running time trial (TT) and race day performance) were measured. These responses were compared to a control sample (n=15). Results show a significant increase (p<0.05) in training load (3899.4 ± 2517.8) four weeks prior to the event. Fatigue scores significantly increased (p<0.05) concurrently with this significant increase (p<0.05) in training. TT performance did not significantly (p<0.05) alter during the time course of training. It was however strongly correlated to training load (R2=0.85) and modestly related to race performance (R2=0.65). The signs and symptoms of upper respiratory tract infections (URTI) were prevalent during the training period, decreasing during the taper and race period. Large standard deviations were found within the majority of the responses. During the final two weeks of preparation, tension scores were significantly increased (p<0.05) while training load significantly decreased (p<0.05) during the final week of preparation. Cortisol increased significantly (p<0.05) immediately post race (0.507±0.15
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Physiological, perceptual and performance responses during cricket activity
- Authors: King, Gregory Allen
- Date: 2003
- Subjects: Cricket , Sports -- Psychological aspects , Sports -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5131 , http://hdl.handle.net/10962/d1005210 , Cricket , Sports -- Psychological aspects , Sports -- Physiological aspects
- Description: The present study sought to determine the influence of environmental conditions and protective clothing on physiological, perceptual and performance responses during batting activity. The investigation examined mean skin temperature, average heart rate, estimated sweat rate, rating of perceived exertion, thermal sensation rating, average sprint time and pre-post choice reaction time. Twenty-five cricketers (18-22 yr, 73.1 ± 9.6 kg, 1768 ± 75 mm, 12.6 ± 3.1% body fat, 1.89 ± 0.16 m2) performed a work-bout consisting of a seven-Over batting period, during which time they faced deliveries from a bowling machine and performed two shuttle runs every third ball to total four sprints per Over. Trials were carried out under High-stress (23.8 ± 2.2 °C) and Low-stress (13.3 ± 1.9 °C) environmental conditions (WBGT). Within each environmental condition subjects performed the test wearing full protective batting gear and no protective gear. Thus, four specific conditions were examined; high full-gear (HFG), high no-gear (HNG), low full-gear (LFG) and low no-gear (LNG). Two-way ANOVAs were calculated to determine whether there were differences between environmental conditions and whether differences existed between the clothing conditions. One-way ANOVAs were utilised to compute differences between the four specific conditions combining clothing and environment. High environmental stress and wearing protective clothing caused batsmen to experience significant physiological strain. The environment was the greatest stressor, with the protective gear exacerbating these effects. However, when padding covered skin areas directly, this was the primary skin temperature stressor, particularly later in the activity. For skin temperature and heart rate, the strain was the most pronounced at the end of the trials. Perceptual responses indicated that the protective gear had no influence on effort sense, thermal sensation or thermal comfort. However, environmental conditions had an effect, and High-stress conditions resulted in significantly higher perceptions of effort, elevated sensations of heat and greater thermal discomfort. Effort was perceived to be greatest towards the end of the trial. There were mixed findings for performance factors. In general sprint performance was not hindered by environmental stress, but protective clothing caused a reduction in several sprint times. Choice reaction times were for the most part unaffected by either environment or clothing and few differences were observed between pre and post times. It is contended that intense short duration batting activity, likely encountered during one-day participation, imposes a stress on batsmen. The stress is greater when conditions are warmer and protective padding is worn, although it is not sufficient to impede choice reaction time. However, protective gear did have a deleterious effect on sprint performance.
- Full Text:
- Authors: King, Gregory Allen
- Date: 2003
- Subjects: Cricket , Sports -- Psychological aspects , Sports -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5131 , http://hdl.handle.net/10962/d1005210 , Cricket , Sports -- Psychological aspects , Sports -- Physiological aspects
- Description: The present study sought to determine the influence of environmental conditions and protective clothing on physiological, perceptual and performance responses during batting activity. The investigation examined mean skin temperature, average heart rate, estimated sweat rate, rating of perceived exertion, thermal sensation rating, average sprint time and pre-post choice reaction time. Twenty-five cricketers (18-22 yr, 73.1 ± 9.6 kg, 1768 ± 75 mm, 12.6 ± 3.1% body fat, 1.89 ± 0.16 m2) performed a work-bout consisting of a seven-Over batting period, during which time they faced deliveries from a bowling machine and performed two shuttle runs every third ball to total four sprints per Over. Trials were carried out under High-stress (23.8 ± 2.2 °C) and Low-stress (13.3 ± 1.9 °C) environmental conditions (WBGT). Within each environmental condition subjects performed the test wearing full protective batting gear and no protective gear. Thus, four specific conditions were examined; high full-gear (HFG), high no-gear (HNG), low full-gear (LFG) and low no-gear (LNG). Two-way ANOVAs were calculated to determine whether there were differences between environmental conditions and whether differences existed between the clothing conditions. One-way ANOVAs were utilised to compute differences between the four specific conditions combining clothing and environment. High environmental stress and wearing protective clothing caused batsmen to experience significant physiological strain. The environment was the greatest stressor, with the protective gear exacerbating these effects. However, when padding covered skin areas directly, this was the primary skin temperature stressor, particularly later in the activity. For skin temperature and heart rate, the strain was the most pronounced at the end of the trials. Perceptual responses indicated that the protective gear had no influence on effort sense, thermal sensation or thermal comfort. However, environmental conditions had an effect, and High-stress conditions resulted in significantly higher perceptions of effort, elevated sensations of heat and greater thermal discomfort. Effort was perceived to be greatest towards the end of the trial. There were mixed findings for performance factors. In general sprint performance was not hindered by environmental stress, but protective clothing caused a reduction in several sprint times. Choice reaction times were for the most part unaffected by either environment or clothing and few differences were observed between pre and post times. It is contended that intense short duration batting activity, likely encountered during one-day participation, imposes a stress on batsmen. The stress is greater when conditions are warmer and protective padding is worn, although it is not sufficient to impede choice reaction time. However, protective gear did have a deleterious effect on sprint performance.
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A comparative study of acute responses to running in elite black and white marathon athletes
- Authors: Bosch, Andrew Norman
- Date: 1985
- Subjects: Athletics , Sports -- Physiological aspects , Running races , Marathon running , Marathon running -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5099 , http://hdl.handle.net/10962/d1001839 , Athletics , Sports -- Physiological aspects , Running races , Marathon running , Marathon running -- Physiological aspects
- Description: Experienced male marathon runners, 9 black and 10 white, with marathon times of 2 hours 45 minutes or faster, acted as subjects for the study, the purpose of which was to determine whether black runners are better suited to marathon running than whites. Body composition was determined by anthropometry. Maximal oxygen uptake (VO₂ max) and other physiological variables were measured during a continuous, speed-incremented treadmill protocol using a computer-aided data acquisition system. Subjects also ran a simulated marathon at 92.5% of the running speed at which the ventilatory threshold (VT) occurred. Physiological, gait and RPE variables were measured at 10 minute intervals during the marathon. Major findings are detailed below:- The VO₂, max averaged 60.4 ∓ 6.5 and 63.2 ∓ 2.9 mI. kg⁻¹.min⁻¹ in the black and white runners respectively and was highly correlated with best marathon race time (r = 0.86 and 0.85 respectively) and VT (r = 0.84 and 0.60 respectively) (p < 0.05). No significant differences existed between the groups in submaximal oxygen uptake (VO₂,) or % VO₂ max utilised at 16 km.hr⁻¹, but the estimated % VO₂ max utilised during a marathon race was higher in the black (89.0 ∓ 5.5%) than the white runners (81. 5 ∓ 3.1%) {p .( 0.05). The % VO₂ max utilised at 16 km.hr⁻¹ (84.8 ∓ 9.1 and 78.6 ∓ 5.8% in the black and white runners respectively) was significantly correlated with the % VO₂, max utilised while racing in the white (81.5 ∓ 3.1%) (r = 0.70) (p < 0.05), but not the black runners (89.0 ∓ 5.5%). The VT occurred at 82.7 ∓ 7.7 and 75.6 :∓ 6.2% VO₂; max in the black and white groups respectively (p < 0.05). Post-marathon blood lactic acid levels were lower in the black (1.30 ∓ 0.26 mmo1.l⁻¹) than the white runners (1.59 ∓ 0.20 mmol.l⁻¹). The respiratory exchange ratio (R) was higher in the blacks than whites when running at 16 km.hr ⁻¹ (1.03 ∓ 0.07 and 0.98 ∓ 0.03 respectively) and during the marathon (p < 0.05). There was no significant difference in pulmonary minute ventilation (Vı) between the groups, but breathing frequency (f) was higher in the black (59 ∓ 12 breaths.min⁻¹) than the white runners (45 ∓ 8 breaths. min⁻¹ ) and tidal volume (V⊤) lower in the black ( 1.33 ∓ 0.16 l.breath⁻¹) than the white runners (1.75 ∓ 0.36 I.breath⁻¹) during submaximal running at 16 km. hr⁻¹ (p < 0.05). The same trend was observed during the marathon run. During the time-course of the marathon f increased and V⊤ decreased In both groups (p < 0.05). Stroke volume decreased and heart rate increased In both groups during the time-course of the marathon (p< 0.05). Cardiac output was therefore maintained. Thermal responses were similar in the two groups. A significant increase in rectal temperature coincided with a decrease in skin temperature and may have been related to an increase in f (r = 0.86 and 0.67 in the blacks and whites respectively), H/R (r = 0.70 and 0.67 respectively) and "local" (leg) RPE (r = 0.84 and 0.82 respectively). It was concluded that black runners were able to run marathon races at a higher % VO₂ more than whites due to the blacks having lower blood lactic acid levels when running at a similar % VO₂ max. Given similar maximal oxygen uptakes, this would enable blacks to run faster. Cardiopulmonary adjustments occur during the time-course of a marathon which maintains Q and Vı
- Full Text:
- Authors: Bosch, Andrew Norman
- Date: 1985
- Subjects: Athletics , Sports -- Physiological aspects , Running races , Marathon running , Marathon running -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5099 , http://hdl.handle.net/10962/d1001839 , Athletics , Sports -- Physiological aspects , Running races , Marathon running , Marathon running -- Physiological aspects
- Description: Experienced male marathon runners, 9 black and 10 white, with marathon times of 2 hours 45 minutes or faster, acted as subjects for the study, the purpose of which was to determine whether black runners are better suited to marathon running than whites. Body composition was determined by anthropometry. Maximal oxygen uptake (VO₂ max) and other physiological variables were measured during a continuous, speed-incremented treadmill protocol using a computer-aided data acquisition system. Subjects also ran a simulated marathon at 92.5% of the running speed at which the ventilatory threshold (VT) occurred. Physiological, gait and RPE variables were measured at 10 minute intervals during the marathon. Major findings are detailed below:- The VO₂, max averaged 60.4 ∓ 6.5 and 63.2 ∓ 2.9 mI. kg⁻¹.min⁻¹ in the black and white runners respectively and was highly correlated with best marathon race time (r = 0.86 and 0.85 respectively) and VT (r = 0.84 and 0.60 respectively) (p < 0.05). No significant differences existed between the groups in submaximal oxygen uptake (VO₂,) or % VO₂ max utilised at 16 km.hr⁻¹, but the estimated % VO₂ max utilised during a marathon race was higher in the black (89.0 ∓ 5.5%) than the white runners (81. 5 ∓ 3.1%) {p .( 0.05). The % VO₂ max utilised at 16 km.hr⁻¹ (84.8 ∓ 9.1 and 78.6 ∓ 5.8% in the black and white runners respectively) was significantly correlated with the % VO₂, max utilised while racing in the white (81.5 ∓ 3.1%) (r = 0.70) (p < 0.05), but not the black runners (89.0 ∓ 5.5%). The VT occurred at 82.7 ∓ 7.7 and 75.6 :∓ 6.2% VO₂; max in the black and white groups respectively (p < 0.05). Post-marathon blood lactic acid levels were lower in the black (1.30 ∓ 0.26 mmo1.l⁻¹) than the white runners (1.59 ∓ 0.20 mmol.l⁻¹). The respiratory exchange ratio (R) was higher in the blacks than whites when running at 16 km.hr ⁻¹ (1.03 ∓ 0.07 and 0.98 ∓ 0.03 respectively) and during the marathon (p < 0.05). There was no significant difference in pulmonary minute ventilation (Vı) between the groups, but breathing frequency (f) was higher in the black (59 ∓ 12 breaths.min⁻¹) than the white runners (45 ∓ 8 breaths. min⁻¹ ) and tidal volume (V⊤) lower in the black ( 1.33 ∓ 0.16 l.breath⁻¹) than the white runners (1.75 ∓ 0.36 I.breath⁻¹) during submaximal running at 16 km. hr⁻¹ (p < 0.05). The same trend was observed during the marathon run. During the time-course of the marathon f increased and V⊤ decreased In both groups (p < 0.05). Stroke volume decreased and heart rate increased In both groups during the time-course of the marathon (p< 0.05). Cardiac output was therefore maintained. Thermal responses were similar in the two groups. A significant increase in rectal temperature coincided with a decrease in skin temperature and may have been related to an increase in f (r = 0.86 and 0.67 in the blacks and whites respectively), H/R (r = 0.70 and 0.67 respectively) and "local" (leg) RPE (r = 0.84 and 0.82 respectively). It was concluded that black runners were able to run marathon races at a higher % VO₂ more than whites due to the blacks having lower blood lactic acid levels when running at a similar % VO₂ max. Given similar maximal oxygen uptakes, this would enable blacks to run faster. Cardiopulmonary adjustments occur during the time-course of a marathon which maintains Q and Vı
- Full Text:
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