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:
- Date Issued: 2013
- 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:
- Date Issued: 2013
Musculoskeletal and perceptual responses of batsmen comparing high- and moderate-volume sprints between the wickets
- Authors: Sheppard, Bronwyn Jane
- Date: 2012
- Subjects: Cricket -- Batting -- Physiological aspects , Cricket injuries , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5171 , http://hdl.handle.net/10962/d1016366
- Description: Background: Literature has associated repeated eccentric muscle actions with increased muscle damage of the muscles involved. Eccentric actions are typical in sports which are ‘stop-start’ in nature requiring rapid acceleration and deceleration, typical of a batting activity in cricket. Ultra-structural damage of the skeletal muscle as a consequence of repeated decelerating activities is associated with performance decrements, particularly muscle strength and sprinting speeds. This suggests that eccentric strength decrements may provide an indication for the development of muscle strain injuries during these activities. Despite these findings, limited research has identified the specific musculoskeletal demands placed on cricket batsmen, particularly with reference to various match intensities. Objective: The present study, therefore, sought to determine the specific musculoskeletal, physiological and perceptual demands placed on specialised batsmen during two work bouts of different intensities; one representing a highintensity work bout and the other a moderate-intensity work bout. The dependent variables of interest were muscle activation, isokinetic strength changes, heart rate, ‘central’ and ‘local’ ratings of perceived exertion (RPE), body discomfort and performance. Methods: The two experimental conditions, representative of a high- (HVR) and moderate-volume running (MVR) batting protocol, required players to perform a simulated batting work bout of either twelve or six runs an over, within a laboratory setting. Selected physiological, perceptual and performance measures were collected at specific time intervals throughout the work bout while the biophysical measures were collected prior to, and following both protocols. Results: Of the variables measured, heart rate, ‘central’ and ‘local’ RPE values were observed to increase significantly (p<0.05) over time. This increase was greater as a consequence of the HVR in comparison to the MVR. No change in sprint times was documented during the MVR, in contrast, significant (p<0.05) increases over time were observed during the HVR, further highlighting the elevated demands associated with this condition. In addition, an ‘end spurt’ was observed particularly following the HVR condition, suggesting athletes were conserving themselves through the adoption of a pacing strategy. Reductions in biceps femoris and semitendinosus muscle activation levels were observed following the HVR. This was further supported by the significantly greater levels of semitendinosus activation following the MVR when compared to the HVR. Peak concentric and eccentric knee extensor (EXT) (-17.17% and -16.07% respectively) and eccentric flexor (FLEX) (- 17.49%) values decreased significantly (p<0.05) following the HVR at 60°.s-1. In addition, concentric and eccentric total work produced by the flexors and eccentric extensors resulted in significantly (p<0.05) lower values due to the HVR. Conclusion: The intermittent high-volume batting work bout elicited elevated mean heart rates, perceived ratings of cardiovascular and muscular effort and sprint times. Furthermore, hamstring activation levels and muscle strength, particularly concentric strength of the dominant lower limb were negatively affected by the HVR condition. These results suggest elevated demands were placed on the hamstring musculature as a consequence of the HVR condition, indicating a greater degree of musculoskeletal strain and increased injury risk associated with running between the wickets at this intensity, representative of an aggressive batting scenario.
- Full Text:
- Date Issued: 2012
- Authors: Sheppard, Bronwyn Jane
- Date: 2012
- Subjects: Cricket -- Batting -- Physiological aspects , Cricket injuries , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5171 , http://hdl.handle.net/10962/d1016366
- Description: Background: Literature has associated repeated eccentric muscle actions with increased muscle damage of the muscles involved. Eccentric actions are typical in sports which are ‘stop-start’ in nature requiring rapid acceleration and deceleration, typical of a batting activity in cricket. Ultra-structural damage of the skeletal muscle as a consequence of repeated decelerating activities is associated with performance decrements, particularly muscle strength and sprinting speeds. This suggests that eccentric strength decrements may provide an indication for the development of muscle strain injuries during these activities. Despite these findings, limited research has identified the specific musculoskeletal demands placed on cricket batsmen, particularly with reference to various match intensities. Objective: The present study, therefore, sought to determine the specific musculoskeletal, physiological and perceptual demands placed on specialised batsmen during two work bouts of different intensities; one representing a highintensity work bout and the other a moderate-intensity work bout. The dependent variables of interest were muscle activation, isokinetic strength changes, heart rate, ‘central’ and ‘local’ ratings of perceived exertion (RPE), body discomfort and performance. Methods: The two experimental conditions, representative of a high- (HVR) and moderate-volume running (MVR) batting protocol, required players to perform a simulated batting work bout of either twelve or six runs an over, within a laboratory setting. Selected physiological, perceptual and performance measures were collected at specific time intervals throughout the work bout while the biophysical measures were collected prior to, and following both protocols. Results: Of the variables measured, heart rate, ‘central’ and ‘local’ RPE values were observed to increase significantly (p<0.05) over time. This increase was greater as a consequence of the HVR in comparison to the MVR. No change in sprint times was documented during the MVR, in contrast, significant (p<0.05) increases over time were observed during the HVR, further highlighting the elevated demands associated with this condition. In addition, an ‘end spurt’ was observed particularly following the HVR condition, suggesting athletes were conserving themselves through the adoption of a pacing strategy. Reductions in biceps femoris and semitendinosus muscle activation levels were observed following the HVR. This was further supported by the significantly greater levels of semitendinosus activation following the MVR when compared to the HVR. Peak concentric and eccentric knee extensor (EXT) (-17.17% and -16.07% respectively) and eccentric flexor (FLEX) (- 17.49%) values decreased significantly (p<0.05) following the HVR at 60°.s-1. In addition, concentric and eccentric total work produced by the flexors and eccentric extensors resulted in significantly (p<0.05) lower values due to the HVR. Conclusion: The intermittent high-volume batting work bout elicited elevated mean heart rates, perceived ratings of cardiovascular and muscular effort and sprint times. Furthermore, hamstring activation levels and muscle strength, particularly concentric strength of the dominant lower limb were negatively affected by the HVR condition. These results suggest elevated demands were placed on the hamstring musculature as a consequence of the HVR condition, indicating a greater degree of musculoskeletal strain and increased injury risk associated with running between the wickets at this intensity, representative of an aggressive batting scenario.
- Full Text:
- Date Issued: 2012
The nature and incidence of fast bowling injuries at an elite, junior level and the associated risk factors
- Authors: Davies, Roxanne
- Date: 2008
- Subjects: Cricket injuries , Cricket -- Bowling , Cricket injuries -- Prevention
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10098 , http://hdl.handle.net/10948/660 , Cricket injuries , Cricket -- Bowling , Cricket injuries -- Prevention
- Description: Fast bowlers are especially prone to injury as they perform their bowling techniques repetitively at very high intensities. The fast bowling action in the past has been described as a highly explosive activity that produces high levels of stress and strain on the body. The aim of this study was to compile an injury profile of 46 fast bowlers aged 11 to 18, and to identify the associated risk factors for injury during an academy cricket season. A descriptive correlational research design was utilised. Subjects were selected according to age and fast bowling ability. These subjects were observed for one academy cricket season (March to November). Three testing sessions occurred during this time (T1, T2 and T3). Each subject completed two questionnaires: i) bowler history (at T1) and ii) injury history (at T1, T2, and T3). These assisted in grouping the subjects according to their responses into one of three injury classifications (uninjured = S1; injured but able to play = S2; injured and unable to play = S3). Anthropometric and postural data for the entire group of fast bowlers were also collected pre-season (T1). Physical fitness screenings were also conducted during each of the three testing sessions to establish any relationship between the fitness of each fast bowler and the occurrence of injuries. Additional factors assessed during the season were bowling techniques and bowling workload. Statistical significance was indicated by p-values less than .05 (p< .05), while practical significance was indicated by either Cohen’s d-values of 0.2 or better (d>0.2) for tests based on sample means or Cramer’s V for tests based on sample frequencies, the values of which depend on the applicable degrees of freedom. All fitness scores as well as bowling workload figures for each testing session were converted to standard T-scores and these in turn were summated to derive overall fitness and workload T-scores. ‘TT’ indicated the overall average score for the entire season. Changes in performances, bowling workload and injury status were analysed using ANOVA and ANCOVA. A regression analysis was also conducted to analyse the relationship between bowling workload and weeks incapacitated. This study found that hyperextension in the knees had the highest incidence of postural deviation injury (43 percent) followed by winged scapula (39 percent). Only 15 percent of the fast bowlers remained injury-free for the duration of the season, while 35 percent of the subjects were at some stage injured to such an extent that they were unable to play. The incidence of serious injury (S3) showed a statistical and moderate practical (V=0.23, d.f. ≥2) significant increase throughout the data collection period (4 percent at T1 to 30 percent at T3). The most common injury was to the knee (41 percent) followed by those to the lower back (37 percent). These injuries occurred mostly during test periods T2 and T3. The nature of injuries were predominantly strains and "other" which accounted for 39 percent of the injuries overall (TT) and had the highest reported incidence during the period T1 to T3. Sprains followed with an overall incidence of 14 percent. Less frequently reported injuries were tears, fractures, bruises and dislocations. The degree of severity of injuries was defined in terms of the number of weeks a player reported being incapacitated as a result of injury during the academy session. During midand end-season bowlers were on average incapacitated approximately one week out of every five due to injury. The statistics for the duration of the study translate to approximately one week incapacitated out of every seven weeks of play. When comparing the S1/S2 bowlers with the S3 group, the S1/S2 bowlers performed consistently better than the S3 bowlers in all the fitness variables tested. However no significant differences (p>.05) in either flexibility or muscle strength were observed. Of the risk factors analysed, bowling workload presented a statistically significant (p<.0005) increased risk for injury. A strong significant positive relationship (p<.0005, R²=.619) was found between weeks incapacitated and bowling workload, supporting the finding that increased bowling workloads show a linear relationship with the increase in the number of weeks incapacitated from normal play. This study concluded that inadequate fitness, high bowling workload and bowling technique all have a multi-factorial role in predisposing a bowler to increased risk for injury. These variables did not act alone, but have all contributed to recurring injuries. The bowling action alone would not have been detrimental if the workloads were not in excess of the recommended guidelines. Furthermore the workload would not have been as detrimental if the bowlers were well conditioned and uninjured. Management of minor injuries and adequate recovery time, coupled with adequate and relevant fitness preparation would better prepare fast bowlers for the demands of the game.
- Full Text:
- Date Issued: 2008
- Authors: Davies, Roxanne
- Date: 2008
- Subjects: Cricket injuries , Cricket -- Bowling , Cricket injuries -- Prevention
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10098 , http://hdl.handle.net/10948/660 , Cricket injuries , Cricket -- Bowling , Cricket injuries -- Prevention
- Description: Fast bowlers are especially prone to injury as they perform their bowling techniques repetitively at very high intensities. The fast bowling action in the past has been described as a highly explosive activity that produces high levels of stress and strain on the body. The aim of this study was to compile an injury profile of 46 fast bowlers aged 11 to 18, and to identify the associated risk factors for injury during an academy cricket season. A descriptive correlational research design was utilised. Subjects were selected according to age and fast bowling ability. These subjects were observed for one academy cricket season (March to November). Three testing sessions occurred during this time (T1, T2 and T3). Each subject completed two questionnaires: i) bowler history (at T1) and ii) injury history (at T1, T2, and T3). These assisted in grouping the subjects according to their responses into one of three injury classifications (uninjured = S1; injured but able to play = S2; injured and unable to play = S3). Anthropometric and postural data for the entire group of fast bowlers were also collected pre-season (T1). Physical fitness screenings were also conducted during each of the three testing sessions to establish any relationship between the fitness of each fast bowler and the occurrence of injuries. Additional factors assessed during the season were bowling techniques and bowling workload. Statistical significance was indicated by p-values less than .05 (p< .05), while practical significance was indicated by either Cohen’s d-values of 0.2 or better (d>0.2) for tests based on sample means or Cramer’s V for tests based on sample frequencies, the values of which depend on the applicable degrees of freedom. All fitness scores as well as bowling workload figures for each testing session were converted to standard T-scores and these in turn were summated to derive overall fitness and workload T-scores. ‘TT’ indicated the overall average score for the entire season. Changes in performances, bowling workload and injury status were analysed using ANOVA and ANCOVA. A regression analysis was also conducted to analyse the relationship between bowling workload and weeks incapacitated. This study found that hyperextension in the knees had the highest incidence of postural deviation injury (43 percent) followed by winged scapula (39 percent). Only 15 percent of the fast bowlers remained injury-free for the duration of the season, while 35 percent of the subjects were at some stage injured to such an extent that they were unable to play. The incidence of serious injury (S3) showed a statistical and moderate practical (V=0.23, d.f. ≥2) significant increase throughout the data collection period (4 percent at T1 to 30 percent at T3). The most common injury was to the knee (41 percent) followed by those to the lower back (37 percent). These injuries occurred mostly during test periods T2 and T3. The nature of injuries were predominantly strains and "other" which accounted for 39 percent of the injuries overall (TT) and had the highest reported incidence during the period T1 to T3. Sprains followed with an overall incidence of 14 percent. Less frequently reported injuries were tears, fractures, bruises and dislocations. The degree of severity of injuries was defined in terms of the number of weeks a player reported being incapacitated as a result of injury during the academy session. During midand end-season bowlers were on average incapacitated approximately one week out of every five due to injury. The statistics for the duration of the study translate to approximately one week incapacitated out of every seven weeks of play. When comparing the S1/S2 bowlers with the S3 group, the S1/S2 bowlers performed consistently better than the S3 bowlers in all the fitness variables tested. However no significant differences (p>.05) in either flexibility or muscle strength were observed. Of the risk factors analysed, bowling workload presented a statistically significant (p<.0005) increased risk for injury. A strong significant positive relationship (p<.0005, R²=.619) was found between weeks incapacitated and bowling workload, supporting the finding that increased bowling workloads show a linear relationship with the increase in the number of weeks incapacitated from normal play. This study concluded that inadequate fitness, high bowling workload and bowling technique all have a multi-factorial role in predisposing a bowler to increased risk for injury. These variables did not act alone, but have all contributed to recurring injuries. The bowling action alone would not have been detrimental if the workloads were not in excess of the recommended guidelines. Furthermore the workload would not have been as detrimental if the bowlers were well conditioned and uninjured. Management of minor injuries and adequate recovery time, coupled with adequate and relevant fitness preparation would better prepare fast bowlers for the demands of the game.
- Full Text:
- Date Issued: 2008
Cumulative mild head injury in rugby: cognitive test profiles of professional rugby and cricket players
- Authors: Ancer, Ruth Lauren
- Date: 1999
- Subjects: Head -- Wounds and injuries , Rugby football injuries , Cricket injuries , Cognitive therapy , Neuropsychological tests
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2925 , http://hdl.handle.net/10962/d1002434 , Head -- Wounds and injuries , Rugby football injuries , Cricket injuries , Cognitive therapy , Neuropsychological tests
- Description: This study investigates the effects of cumulative concussive and subconcussive mild head injury on the cognitive functioning of professional rugby players. A comprehensive battery of neuropsychological tests was administered to 26 professional rugby players and a noncontact sport control group of 21 professional cricket players. The test performances of the rugby players were compared to those of the cricket players. Within the rugby group, forward and backline players were compared. An analysis of mean score differences between the rugby and cricket group failed to support the presence of brain damage effects in the rugby group. However, there was significantly increased variability of scores for the rugby players compared with the cricket players on tests particularly sensitive to cognitive deficit associated with mild head injury. This invalidates the null indications of average effects, indicating that a notable proportion of rugby players’ performances were falling off relative to the rest of the rugby players on tests vulnerable to the cognitive effects of diffuse brain damage. Mean score comparisons within the rugby group indicated that it was the subgroup of forward players, in particular, whose test performances revealed deficits suggestive of cerebral damage. Specifically, deficits were found in working memory, visuoperceptual tracking, verbal memory and visual memory, a pattern of deficits commensurate with cumulative mild head injury. The theoretical perspectives of Satz’s (1997) Brain Reserve Capacity Theory and Jordan’s (1997) ‘Shuttle’ model of variability are drawn upon in order to elucidate research findings and suggestions for future research are provided.
- Full Text:
- Date Issued: 1999
- Authors: Ancer, Ruth Lauren
- Date: 1999
- Subjects: Head -- Wounds and injuries , Rugby football injuries , Cricket injuries , Cognitive therapy , Neuropsychological tests
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2925 , http://hdl.handle.net/10962/d1002434 , Head -- Wounds and injuries , Rugby football injuries , Cricket injuries , Cognitive therapy , Neuropsychological tests
- Description: This study investigates the effects of cumulative concussive and subconcussive mild head injury on the cognitive functioning of professional rugby players. A comprehensive battery of neuropsychological tests was administered to 26 professional rugby players and a noncontact sport control group of 21 professional cricket players. The test performances of the rugby players were compared to those of the cricket players. Within the rugby group, forward and backline players were compared. An analysis of mean score differences between the rugby and cricket group failed to support the presence of brain damage effects in the rugby group. However, there was significantly increased variability of scores for the rugby players compared with the cricket players on tests particularly sensitive to cognitive deficit associated with mild head injury. This invalidates the null indications of average effects, indicating that a notable proportion of rugby players’ performances were falling off relative to the rest of the rugby players on tests vulnerable to the cognitive effects of diffuse brain damage. Mean score comparisons within the rugby group indicated that it was the subgroup of forward players, in particular, whose test performances revealed deficits suggestive of cerebral damage. Specifically, deficits were found in working memory, visuoperceptual tracking, verbal memory and visual memory, a pattern of deficits commensurate with cumulative mild head injury. The theoretical perspectives of Satz’s (1997) Brain Reserve Capacity Theory and Jordan’s (1997) ‘Shuttle’ model of variability are drawn upon in order to elucidate research findings and suggestions for future research are provided.
- Full Text:
- Date Issued: 1999
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