Pub Date : 2017-03-16DOI: 10.1080/17461391.2016.1255261
Hyun-Sung An, Gregory C. Jones, Seoungki Kang, G. Welk, Jung-Min Lee
Abstract Wearable activity trackers have become popular for tracking individual’s daily physical activity, but little information is available to substantiate the validity of these devices in step counts. Thirty-five healthy individuals completed three conditions of activity tracker measurement: walking/jogging on a treadmill, walking over-ground on an indoor track, and a 24-hour free-living condition. Participants wore 10 activity trackers at the same time for both treadmill and over-ground protocol. Of these 10 activity trackers three were randomly given for 24-hour free-living condition. Correlations of steps measured to steps observed were r = 0.84 and r = 0.67 on a treadmill and over-ground protocol, respectively. The mean MAPE (mean absolute percentage error) score for all devices and speeds on a treadmill was 8.2% against manually counted steps. The MAPE value was higher for over-ground walking (9.9%) and even higher for the 24-hour free-living period (18.48%) on step counts. Equivalence testing for step count measurement resulted in a significant level within ±5% for the Fitbit Zip, Withings Pulse, and Jawbone UP24 and within ±10% for the Basis B1 band, Garmin VivoFit, and SenseWear Armband Mini. The results show that the Fitbit Zip and Withings Pulse provided the most accurate measures of step count under all three different conditions (i.e. treadmill, over-ground, and 24-hour condition), and considerable variability in accuracy across monitors and also by speeds and conditions.
{"title":"How valid are wearable physical activity trackers for measuring steps?","authors":"Hyun-Sung An, Gregory C. Jones, Seoungki Kang, G. Welk, Jung-Min Lee","doi":"10.1080/17461391.2016.1255261","DOIUrl":"https://doi.org/10.1080/17461391.2016.1255261","url":null,"abstract":"Abstract Wearable activity trackers have become popular for tracking individual’s daily physical activity, but little information is available to substantiate the validity of these devices in step counts. Thirty-five healthy individuals completed three conditions of activity tracker measurement: walking/jogging on a treadmill, walking over-ground on an indoor track, and a 24-hour free-living condition. Participants wore 10 activity trackers at the same time for both treadmill and over-ground protocol. Of these 10 activity trackers three were randomly given for 24-hour free-living condition. Correlations of steps measured to steps observed were r = 0.84 and r = 0.67 on a treadmill and over-ground protocol, respectively. The mean MAPE (mean absolute percentage error) score for all devices and speeds on a treadmill was 8.2% against manually counted steps. The MAPE value was higher for over-ground walking (9.9%) and even higher for the 24-hour free-living period (18.48%) on step counts. Equivalence testing for step count measurement resulted in a significant level within ±5% for the Fitbit Zip, Withings Pulse, and Jawbone UP24 and within ±10% for the Basis B1 band, Garmin VivoFit, and SenseWear Armband Mini. The results show that the Fitbit Zip and Withings Pulse provided the most accurate measures of step count under all three different conditions (i.e. treadmill, over-ground, and 24-hour condition), and considerable variability in accuracy across monitors and also by speeds and conditions.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"60 1","pages":"360 - 368"},"PeriodicalIF":3.2,"publicationDate":"2017-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84004780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-16DOI: 10.1080/17461391.2016.1260641
A. Elbe, J. Wikman, M. Zheng, M. N. Larsen, G. Nielsen, P. Krustrup
Abstract This study investigates the enjoyment and cohesion of school children participating in a school-based high-intensity physical activity (PA) intervention. Both enjoyment and cohesion have been found to be important factors for adherence to regular physical and sport activity, an important outcome of PA interventions. The sample consisted of 300 pupils (mean age: 9.3 years; 52.7% female) assigned to a team sport intervention, an individual sport intervention, or a control group for 10 months. The Physical Activity Enjoyment Scale and Youth Sport Environment Questionnaire were used to measure enjoyment and cohesion. The Yo-Yo IR1C test determined fitness improvements. Results showed that enjoyment and cohesion (social) measured at the beginning of the intervention significantly predict fitness improvements achieved after 10 months. No differing developmental effects over time could be found in the intervention groups with regard to cohesion and enjoyment when comparing them to the control group. However, enjoyment and cohesion (social) significantly decreased in the groups that performed individual sports. Team sports seem to be more advantageous for the development of enjoyment and cohesion, which are both factors that positively impact the health outcomes of the intervention.
{"title":"The importance of cohesion and enjoyment for the fitness improvement of 8–10-year-old children participating in a team and individual sport school-based physical activity intervention","authors":"A. Elbe, J. Wikman, M. Zheng, M. N. Larsen, G. Nielsen, P. Krustrup","doi":"10.1080/17461391.2016.1260641","DOIUrl":"https://doi.org/10.1080/17461391.2016.1260641","url":null,"abstract":"Abstract This study investigates the enjoyment and cohesion of school children participating in a school-based high-intensity physical activity (PA) intervention. Both enjoyment and cohesion have been found to be important factors for adherence to regular physical and sport activity, an important outcome of PA interventions. The sample consisted of 300 pupils (mean age: 9.3 years; 52.7% female) assigned to a team sport intervention, an individual sport intervention, or a control group for 10 months. The Physical Activity Enjoyment Scale and Youth Sport Environment Questionnaire were used to measure enjoyment and cohesion. The Yo-Yo IR1C test determined fitness improvements. Results showed that enjoyment and cohesion (social) measured at the beginning of the intervention significantly predict fitness improvements achieved after 10 months. No differing developmental effects over time could be found in the intervention groups with regard to cohesion and enjoyment when comparing them to the control group. However, enjoyment and cohesion (social) significantly decreased in the groups that performed individual sports. Team sports seem to be more advantageous for the development of enjoyment and cohesion, which are both factors that positively impact the health outcomes of the intervention.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"6 1","pages":"343 - 350"},"PeriodicalIF":3.2,"publicationDate":"2017-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85964369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-16DOI: 10.1080/17461391.2016.1221471
Sebastian Fischer, Claudia Braun, A. Kibele
Abstract In the past, studies and book recommendations on relay starts in swimming have been predominantly focused on the change-over time (COT) as a performance criterion. Aside from the circular backswing start with parallel foot placement, few studies have analysed differences in the take-off movement including step approaches as well. Although trends could be identified, the results remained still somewhat inconclusive. In contrast, no study has examined as has examined whether a reduction of COT in between wall contact of the income swimmer and the take-off of the outgoing swimmer is an optimal relay start strategy, as advocated by various swimming experts. Therefore, the purpose of this study was to compare two different relay start strategies: offensive strategy minimizing COT and conservative strategy to maximize horizontal peak force (HPF). In this regard, a learning intervention with 24 elite-level swimmers (12 females, 12 male) was conducted to compare both strategies regarding relay start time, HPF and COT. Subjects were randomly assigned to two feedback groups: COT versus HPF at take-off. The results of this study showed a clear advantage for HPF feedback for relay start performance measured by wall contact of the incoming swimmer and head passage at 7.5 m of the outgoing swimmer. In addition, similar reductions in COTs were found in both training groups. In conclusion, swimmers should focus on force production rather than minimizing COT. For the latter, deteriorating consequences for force production must be considered.
{"title":"Learning relay start strategies in swimming: What feedback is best?","authors":"Sebastian Fischer, Claudia Braun, A. Kibele","doi":"10.1080/17461391.2016.1221471","DOIUrl":"https://doi.org/10.1080/17461391.2016.1221471","url":null,"abstract":"Abstract In the past, studies and book recommendations on relay starts in swimming have been predominantly focused on the change-over time (COT) as a performance criterion. Aside from the circular backswing start with parallel foot placement, few studies have analysed differences in the take-off movement including step approaches as well. Although trends could be identified, the results remained still somewhat inconclusive. In contrast, no study has examined as has examined whether a reduction of COT in between wall contact of the income swimmer and the take-off of the outgoing swimmer is an optimal relay start strategy, as advocated by various swimming experts. Therefore, the purpose of this study was to compare two different relay start strategies: offensive strategy minimizing COT and conservative strategy to maximize horizontal peak force (HPF). In this regard, a learning intervention with 24 elite-level swimmers (12 females, 12 male) was conducted to compare both strategies regarding relay start time, HPF and COT. Subjects were randomly assigned to two feedback groups: COT versus HPF at take-off. The results of this study showed a clear advantage for HPF feedback for relay start performance measured by wall contact of the incoming swimmer and head passage at 7.5 m of the outgoing swimmer. In addition, similar reductions in COTs were found in both training groups. In conclusion, swimmers should focus on force production rather than minimizing COT. For the latter, deteriorating consequences for force production must be considered.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"27 1","pages":"257 - 263"},"PeriodicalIF":3.2,"publicationDate":"2017-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86624922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-16DOI: 10.1080/17461391.2016.1236840
Paige E Rice, Courtney L. Goodman, Christopher R. Capps, N. Triplett, T. Erickson, J. Mcbride
Abstract The purpose of this study was to compare force– and power–time curve variables during jumping between Division I strength-matched male and female basketball athletes. Males (n = 8) and females (n = 8) were strength matched by testing a one-repetition maximum (1RM) back squat. 1RM back squat values were normalised to body mass in order to demonstrate that strength differences were a function of body mass alone. Subjects performed three countermovement jumps (CMJ) at maximal effort. Absolute and relative force– and power–time curve variables from the CMJs were analysed between males and females. Average force– and power–time curves were generated for all subjects. Jump height was significantly greater (p ≤ .05) in males than females. Absolute force was higher in males during the concentric phase, but not significantly different (p ≥ .05) when normalised to body mass. Significance was found in absolute concentric impulse between sexes, but not when analysed relative to body mass. Rate of force development, rate of power development, relative peak force, and work were not significantly different between sexes. Males had significantly greater impulse during the eccentric phase as well as peak power (PP) during the concentric phase of the CMJ than did females in both absolute and relative terms. It is concluded that sex differences are not a determining factor in measured force during a CMJ when normalised to body mass between strength-matched subjects. However, eccentric phase impulse and concentric phase PP appear to be influenced by sex differences independent of matching strength levels.
{"title":"Force– and power–time curve comparison during jumping between strength-matched male and female basketball players","authors":"Paige E Rice, Courtney L. Goodman, Christopher R. Capps, N. Triplett, T. Erickson, J. Mcbride","doi":"10.1080/17461391.2016.1236840","DOIUrl":"https://doi.org/10.1080/17461391.2016.1236840","url":null,"abstract":"Abstract The purpose of this study was to compare force– and power–time curve variables during jumping between Division I strength-matched male and female basketball athletes. Males (n = 8) and females (n = 8) were strength matched by testing a one-repetition maximum (1RM) back squat. 1RM back squat values were normalised to body mass in order to demonstrate that strength differences were a function of body mass alone. Subjects performed three countermovement jumps (CMJ) at maximal effort. Absolute and relative force– and power–time curve variables from the CMJs were analysed between males and females. Average force– and power–time curves were generated for all subjects. Jump height was significantly greater (p ≤ .05) in males than females. Absolute force was higher in males during the concentric phase, but not significantly different (p ≥ .05) when normalised to body mass. Significance was found in absolute concentric impulse between sexes, but not when analysed relative to body mass. Rate of force development, rate of power development, relative peak force, and work were not significantly different between sexes. Males had significantly greater impulse during the eccentric phase as well as peak power (PP) during the concentric phase of the CMJ than did females in both absolute and relative terms. It is concluded that sex differences are not a determining factor in measured force during a CMJ when normalised to body mass between strength-matched subjects. However, eccentric phase impulse and concentric phase PP appear to be influenced by sex differences independent of matching strength levels.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"3 2 1","pages":"286 - 293"},"PeriodicalIF":3.2,"publicationDate":"2017-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78636114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-16DOI: 10.1080/17461391.2016.1230892
Erica J Roelofs, A. Smith‐Ryan, E. Trexler, K. Hirsch, M. Mock
Abstract The effects of pomegranate extract (PE) supplementation were evaluated on high-intensity exercise performance, blood flow, vessel diameter, oxygen saturation (SPO2), heart rate (HR), and blood pressure (BP). In a randomized, crossover design, nineteen recreationally resistance-trained participants were randomly assigned to PE (1000 mg) or placebo (PL), which were consumed 30 min prior to a repeated sprint ability (RSA) test and repetitions to fatigue (RTF) on bench and leg press. The RSA consisted of ten six-second sprints on a friction-loaded cycle ergometer with 30 s recovery. Brachial artery blood flow and vessel diameter were assessed by ultrasound. Blood flow, vessel diameter, SPO2, HR, and BP were assessed at baseline, 30 min post ingestion, immediately post exercise (IPost), and 30 min post exercise (30minPost). With PE, blood flow significantly increased IPost RSA (mean difference = 18.49 mL min−1; P < .05), and IPost and 30minPost RTF (P < .05) according to confidence intervals (CI). Vessel diameter increased significantly 30minPost RSA according to CI and resulted in a significant interaction IPost and 30minPost RTF (P < .05). With PE, according to CI, average and peak power output increased significantly in sprint 5 of the RSA (P < .05). There was no significant difference between PE and PL for bench (P = .25) or leg press (P = .15) repetitions. Acute PE supplementation enhanced vessel diameter and blood flow, suggesting possible exercise performance enhancement from increased delivery of substrates and oxygen. The acute timing and capsule form of PE may be advantageous to athletic populations due to ergogenic effects, taste, and convenience.
{"title":"Effects of pomegranate extract on blood flow and vessel diameter after high-intensity exercise in young, healthy adults","authors":"Erica J Roelofs, A. Smith‐Ryan, E. Trexler, K. Hirsch, M. Mock","doi":"10.1080/17461391.2016.1230892","DOIUrl":"https://doi.org/10.1080/17461391.2016.1230892","url":null,"abstract":"Abstract The effects of pomegranate extract (PE) supplementation were evaluated on high-intensity exercise performance, blood flow, vessel diameter, oxygen saturation (SPO2), heart rate (HR), and blood pressure (BP). In a randomized, crossover design, nineteen recreationally resistance-trained participants were randomly assigned to PE (1000 mg) or placebo (PL), which were consumed 30 min prior to a repeated sprint ability (RSA) test and repetitions to fatigue (RTF) on bench and leg press. The RSA consisted of ten six-second sprints on a friction-loaded cycle ergometer with 30 s recovery. Brachial artery blood flow and vessel diameter were assessed by ultrasound. Blood flow, vessel diameter, SPO2, HR, and BP were assessed at baseline, 30 min post ingestion, immediately post exercise (IPost), and 30 min post exercise (30minPost). With PE, blood flow significantly increased IPost RSA (mean difference = 18.49 mL min−1; P < .05), and IPost and 30minPost RTF (P < .05) according to confidence intervals (CI). Vessel diameter increased significantly 30minPost RSA according to CI and resulted in a significant interaction IPost and 30minPost RTF (P < .05). With PE, according to CI, average and peak power output increased significantly in sprint 5 of the RSA (P < .05). There was no significant difference between PE and PL for bench (P = .25) or leg press (P = .15) repetitions. Acute PE supplementation enhanced vessel diameter and blood flow, suggesting possible exercise performance enhancement from increased delivery of substrates and oxygen. The acute timing and capsule form of PE may be advantageous to athletic populations due to ergogenic effects, taste, and convenience.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"93 1","pages":"317 - 325"},"PeriodicalIF":3.2,"publicationDate":"2017-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75283929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-07DOI: 10.1080/17461391.2016.1245788
S. Cotterill, R. Cheetham
Abstract The captain is perceived to be an important member of the leadership structure within teams across many professional sports. However, while there is a general acceptance that this is the case, there is very little research exploring the role and associated demands at an elite level. As a result, the aim of this study was to explore the captaincy experiences of elite professional rugby union captains. The participants were eight male captains purposefully sampled for this study. Participants were interviewed individually to gain an understanding of each participant’s captaincy experiences. The data were thematically analysed using interpretative phenomenological analysis. Nine super-ordinate themes emerged in the study: role, skills, requirements, challenges, the coach, development, experience, context, and approach. Results suggest that the captaincy role is broader than previously highlighted, particularly at the elite level. Also, the study highlights inconsistencies in the selection of captains and a lack of formal developmental support for elite rugby captains. As a result, future research should explore the development of specific evidence-based approaches to captain selection and development.
{"title":"The experience of captaincy in professional sport: The case of elite professional rugby","authors":"S. Cotterill, R. Cheetham","doi":"10.1080/17461391.2016.1245788","DOIUrl":"https://doi.org/10.1080/17461391.2016.1245788","url":null,"abstract":"Abstract The captain is perceived to be an important member of the leadership structure within teams across many professional sports. However, while there is a general acceptance that this is the case, there is very little research exploring the role and associated demands at an elite level. As a result, the aim of this study was to explore the captaincy experiences of elite professional rugby union captains. The participants were eight male captains purposefully sampled for this study. Participants were interviewed individually to gain an understanding of each participant’s captaincy experiences. The data were thematically analysed using interpretative phenomenological analysis. Nine super-ordinate themes emerged in the study: role, skills, requirements, challenges, the coach, development, experience, context, and approach. Results suggest that the captaincy role is broader than previously highlighted, particularly at the elite level. Also, the study highlights inconsistencies in the selection of captains and a lack of formal developmental support for elite rugby captains. As a result, future research should explore the development of specific evidence-based approaches to captain selection and development.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"26 1","pages":"215 - 221"},"PeriodicalIF":3.2,"publicationDate":"2017-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81477078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-07DOI: 10.1080/17461391.2016.1251496
A. Swartz, N. Miller, Young Cho, Whitney A. Welch, S. Strath
Abstract The aim of this study is to determine changes in sedentary behaviour in response to extensive aerobic exercise training. Participants included adults who self-selected to run a marathon. Sedentary behaviour, total activity counts and physical activity (PA) intensity were assessed (Actigraph GT3X) for seven consecutive days during seven assessment periods (−3, −2, and −1 month prior to the marathon, within 2 weeks of the marathon, and +1, +2, and +3 months after the marathon). Models were fitted with multiple imputation data using the STATA mi module. Random intercept generalized least squares (GLS) regression models were used to determine change in sedentary behaviour with seven waves of repeated measures. Results: Twenty-three individuals (mean ± Sx: 34.4 ± 2.1y, 23.0 ± 1.9% fat, 15 women, 8 men) completed the study. Marathon finishing times ranged from 185 to 344 minutes (253.2 ± 9.6 minutes). Total counts in the vertical axis were 1,729,414 lower one month after the race, compared with two months prior to the race (peak training). Furthermore, counts per minute decreased by 252.7 counts·minute−1 during that same time period. Daily sedentary behaviour did not change over the seven assessment periods, after accounting for age, gender, per cent body fat, wear time, marathon finishing time, and previous marathon experience. This prospective study supports the notion that PA and sedentary behaviours are distinct, showing that sedentary behaviour was not impacted by high levels of aerobic training.
{"title":"A prospective examination of the impact of high levels of exercise training on sedentary behaviour","authors":"A. Swartz, N. Miller, Young Cho, Whitney A. Welch, S. Strath","doi":"10.1080/17461391.2016.1251496","DOIUrl":"https://doi.org/10.1080/17461391.2016.1251496","url":null,"abstract":"Abstract The aim of this study is to determine changes in sedentary behaviour in response to extensive aerobic exercise training. Participants included adults who self-selected to run a marathon. Sedentary behaviour, total activity counts and physical activity (PA) intensity were assessed (Actigraph GT3X) for seven consecutive days during seven assessment periods (−3, −2, and −1 month prior to the marathon, within 2 weeks of the marathon, and +1, +2, and +3 months after the marathon). Models were fitted with multiple imputation data using the STATA mi module. Random intercept generalized least squares (GLS) regression models were used to determine change in sedentary behaviour with seven waves of repeated measures. Results: Twenty-three individuals (mean ± Sx: 34.4 ± 2.1y, 23.0 ± 1.9% fat, 15 women, 8 men) completed the study. Marathon finishing times ranged from 185 to 344 minutes (253.2 ± 9.6 minutes). Total counts in the vertical axis were 1,729,414 lower one month after the race, compared with two months prior to the race (peak training). Furthermore, counts per minute decreased by 252.7 counts·minute−1 during that same time period. Daily sedentary behaviour did not change over the seven assessment periods, after accounting for age, gender, per cent body fat, wear time, marathon finishing time, and previous marathon experience. This prospective study supports the notion that PA and sedentary behaviours are distinct, showing that sedentary behaviour was not impacted by high levels of aerobic training.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"21 1","pages":"222 - 230"},"PeriodicalIF":3.2,"publicationDate":"2017-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85059940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-07DOI: 10.1080/17461391.2016.1225823
Andreas Brännström, Ji-Guo Yu, P. Jonsson, T. Åkerfeldt, M. Stridsberg, M. Svensson
Abstract The present work investigated serum vitamin D (25(OH)D) status in relation to bone and muscle qualities and functions in 19 female soccer players (13–16 years) resident at northern latitude with very low sun exposure (∼32–36 h/month) during winter season (late January to early March). Serum 25(OH)D, parathyroid hormone and bone turnover markers osteocalcin (OC) and beta carboxy-terminal collagen cross-links (β-Ctx), as well as body composition and muscle performance were examined. Hormones were tested using routine laboratory methods. Fat mass, lean mass, and bone mineral density in whole body, as well as femur and lumbar spine were evaluated with dual-energy X-ray absorptiometry. Muscle performance was assessed through isokinetic knee extension and flexion, countermovement jump, and sprint running. 25(OH)D was low (50.5 ± 12.8 nmol l−1), whereas the values of bone turnover markers were markedly high (OC: 59.4 ± 18.6 µg l−1; β-Ctx: 1075 ± 408 ng l−1). All bone and muscle measurements were normal or above normal. 25(OH)D was not significantly correlated with most of the parameters of bone and muscle quality or function, except the knee extension time to peak torque (r = −0.50, p = .03). In conclusion, the level of vitamin D is markedly low in adolescent female soccer players during the winter in Sweden. However, vitamin D levels did not significantly correlate with measures of bone and muscle except a moderate correlation in time to peak torque in the knee extensors. The practical implication of low vitamin D levels in young growing female athletes remains unclear.
摘要本研究调查了19名居住在北纬度冬季(1月下旬至3月初)低日照(32-36小时/月)的女足运动员(13-16岁)血清维生素D (25(OH)D)状态与骨骼和肌肉质量和功能的关系。检测血清25(OH)D、甲状旁腺激素、骨转换标志物骨钙素(OC)和β羧基端胶原交联(β-Ctx)，以及体成分和肌肉性能。激素检测采用常规实验室方法。采用双能x线骨密度仪测定全身脂肪量、瘦肉量、骨密度及股骨、腰椎。肌肉表现通过等速膝关节伸展和屈曲，反动作跳跃和冲刺跑来评估。25(OH)D低(50.5±12.8 nmol l−1)，而骨转换标志物的值明显高(OC: 59.4±18.6µg l−1;β-Ctx: 1075±408 ng l−1)。所有骨骼和肌肉测量正常或高于正常。25(OH)D与大部分骨骼肌质量或功能参数均无显著相关性，但与膝关节伸展至峰值扭矩的时间无关(r = - 0.50, p = .03)。综上所述，瑞典冬季青少年女足球运动员的维生素D水平明显较低。然而，维生素D水平与骨骼和肌肉的测量没有显著相关性，除了在膝关节伸肌达到峰值扭矩的时间上有适度的相关性。年轻女性运动员体内维生素D含量低的实际含义尚不清楚。
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Pub Date : 2017-02-07DOI: 10.1080/17461391.2016.1240238
Aimée C. Smith, J. Roberts, P. Kong, S. Forrester
Abstract Analysing the centre of pressure (COP) and centre of gravity (COG) could reveal stabilising strategies used by golfers throughout the golf swing. This study identified and compared golfers’ COP and COG patterns throughout the golf swing in medial–lateral (ML) and anterior–posterior (AP) directions using principal component analysis (PCA) and examined their relationship to clubhead velocity. Three-dimensional marker trajectories were collected using Vicon motion analysis and force plate data from two Kistler force plates for 22 low-handicap golfers during drives. Golfers’ COG and COP were expressed as a percentage distance between their feet. PCA was performed on COG and COP in ML and AP directions. Relationships between principal component (PC) scores were examined using Pearson correlation and regression analysis used to examine the relationship with clubhead velocity. ML COP movements varied in magnitude (PC1), rate of change and timing (PC2 and PC3). The COP and COG PC1 scores were strongly correlated in both directions (ML: r = 0.90, P < .05; AP: r = 0.81, P < .05). Clubhead velocity, explained by three PCs (74%), related to timing and rate of change in COPML near downswing (PC2 and PC3) and timing of COGML late backswing (PC2). The relationship between COPML and COGML PC1 scores identified extremes of COP and COG patterns in golfers and could indicate a golfer’s dynamic balance. Golfers with earlier movement of COP to the front foot (PC2) and rate of change (PC3) patterns in ML COP, prior to the downswing, may be more likely to generate higher clubhead velocity.
分析压力中心(COP)和重心(COG)可以揭示球手在整个挥杆过程中使用的稳定策略。本研究利用主成分分析(PCA)对高尔夫球手在中外侧(ML)和前后(AP)方向上的COP和COG模式进行了识别和比较，并考察了它们与杆头速度的关系。利用Vicon运动分析和两块Kistler力板数据收集了22名低障碍高尔夫球手在击球过程中的三维标记轨迹。高尔夫球手的COG和COP表示为他们两脚之间距离的百分比。在ML和AP方向上对COG和COP进行PCA。主成分(PC)得分之间的关系使用Pearson相关和回归分析来检验与杆头速度的关系。ML COP运动在幅度(PC1)、变化率和时间(PC2和PC3)上有所不同。COP与COG PC1评分呈双向强相关(ML: r = 0.90, P < 0.05;AP: r = 0.81, P < 0.05)。杆头速度，由三个pc(74%)解释，与COPML近下挥杆(PC2和PC3)和COGML晚后挥杆(PC2)的时间和变化率有关。COPML和COGML PC1分数之间的关系可以识别高尔夫球手的COP和COG模式的极端，并可以指示高尔夫球手的动态平衡。在下挥杆之前，较早地将杆头移到前脚(PC2)和改变速度(PC3)模式的高尔夫球手，可能更有可能产生较高的杆头速度。
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Pub Date : 2017-02-07DOI: 10.1080/17461391.2016.1216169
D. Bishop, Neil Addington, Giorgia D'Innocenzo
Abstract Eye movements are essential for both predictive and reactive control of complex motor skills such as the golf swing. We examined the use of a visually guided learning protocol to retrain an experienced golfer’s point-of-gaze immediately prior to execution of the full golf swing; his swing, and his gaze behaviour, had become established over more than a decade of practice and competition. Performance and eye movement data were obtained, from baseline, through intervention, to retention, for a total of 159 shots struck at a target 200 yards away. Results show that, at baseline, not only was the golfer’s point-of-gaze not at the intended/predicted location, at the top-rear of the ball, but there was also high trial-to-trial variability. A bespoke visual guidance protocol improved his gaze behaviour considerably, in terms of accuracy and consistency – and this was reflected in accuracy and consistency of his shots. Implications of oculomotor interventions for the relearning of established motor skills are discussed.
{"title":"Using visual guidance to retrain an experienced golfer’s gaze: A case study","authors":"D. Bishop, Neil Addington, Giorgia D'Innocenzo","doi":"10.1080/17461391.2016.1216169","DOIUrl":"https://doi.org/10.1080/17461391.2016.1216169","url":null,"abstract":"Abstract Eye movements are essential for both predictive and reactive control of complex motor skills such as the golf swing. We examined the use of a visually guided learning protocol to retrain an experienced golfer’s point-of-gaze immediately prior to execution of the full golf swing; his swing, and his gaze behaviour, had become established over more than a decade of practice and competition. Performance and eye movement data were obtained, from baseline, through intervention, to retention, for a total of 159 shots struck at a target 200 yards away. Results show that, at baseline, not only was the golfer’s point-of-gaze not at the intended/predicted location, at the top-rear of the ball, but there was also high trial-to-trial variability. A bespoke visual guidance protocol improved his gaze behaviour considerably, in terms of accuracy and consistency – and this was reflected in accuracy and consistency of his shots. Implications of oculomotor interventions for the relearning of established motor skills are discussed.","PeriodicalId":12061,"journal":{"name":"European Journal of Sport Science","volume":"78 1","pages":"160 - 167"},"PeriodicalIF":3.2,"publicationDate":"2017-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84064053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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