ORCID Profile
0000-0002-1251-7838
Current Organisations
Rush University Medical Center
,
Hospital for Sick Children
,
Auckland University of Technology
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Publisher: Human Kinetics
Date: 10-2021
Abstract: Purpose : The aim of this study was to map responses over 32 hours following high-load (HL) and moderate-load (ML) half-squat priming. Methods : Fifteen participants completed control, HL (87% 1RM), and ML (65% 1RM) activities in randomized, counterbalanced order. Countermovement jump (CMJ), squat jump (SJ), saliva testosterone, saliva cortisol, and perceptual measures were assessed before and 5 minutes, 8 hours, 24 hours, and 32 hours after each activity. Results are presented as percentage change from baseline and 95% confidence interval (CI). Cliff delta was used to determine threshold for group changes. Results : SJ height increased by 4.5% (CI = 2.2–6.8, Cliff delta = 0.20) 8 hours following HL. CMJ and SJ improved by 6.1% (CI = 2.1–7.8, Cliff delta = 0.27) and 6.5% (CI = 1.2–11.8, Cliff delta = 0.30), respectively, 32 hours after ML. No clear diurnal changes in CMJ or SJ occurred 8 hours following control however, increases of 3.9% (CI = 2.9–9.2, Cliff delta = 0.26) and 4.5% (CI = 0.9–8.1, Cliff delta = 0.24), respectively, were observed after 32 hours. Although diurnal changes in saliva hormone concentration occurred (Cliff delta = 0.37–0.92), the influence of priming was unclear. Perceived “physical feeling” was greater 8 hours following HL (Cliff delta = 0.36) and 32 hours after ML and control (Cliff delta = 0.17–0.34). Conclusions : HL priming in the morning may result in small improvements in jump output and psychophysiological state in the afternoon. Similar improvements were observed in the afternoon the day after ML priming.
Publisher: Elsevier BV
Date: 2021
Publisher: Georg Thieme Verlag KG
Date: 07-2008
Abstract: The aims of the present study were to determine the influence of familiarization on the reliability of power output during a dynamic 30-km cycling trial and to determine the test-retest reliability following a 6-week period. Nine trained male cyclists performed five self-paced 30-km cycling trials, which contained three 250-m sprints and three 1-km sprints. The first three of these trials were performed in consecutive weeks (Week 1, Week 2 and Week 3), while the latter two trials were consecutively conducted 6 wk following (Week 9 and Week 10). Subjects were instructed to complete each sprint, as well as the entire trial in the least time possible. Reproducibility in average power output over the entire 30-km trial for Week 2 and 3 alone (coefficient of variation, CV = 2.4 %, intra-class correlation coefficient, ICC = 0.93) was better than for Week 1 and 2 (CV = 5.5 %, ICC = 0.77) and Week 9 and 10 alone (CV = 5.3 %, ICC = 0.57). These results indicate that high reliability during a dynamic 30-km cycling trial may be obtained after a single familiarization trial when subsequent trials are performed within 7 days. However, if cyclists do not perform trials for six weeks, the same level of reliability is not maintained.
Publisher: Springer Science and Business Media LLC
Date: 08-01-2021
Publisher: Springer Science and Business Media LLC
Date: 2011
DOI: 10.2165/11537690-000000000-00000
Abstract: This series of reviews focuses on the most important neuromuscular function in many sport performances, the ability to generate maximal muscular power. Part 1 focuses on the factors that affect maximal power production, while part 2, which will follow in a forthcoming edition of Sports Medicine, explores the practical application of these findings by reviewing the scientific literature relevant to the development of training programmes that most effectively enhance maximal power production. The ability of the neuromuscular system to generate maximal power is affected by a range of interrelated factors. Maximal muscular power is defined and limited by the force-velocity relationship and affected by the length-tension relationship. The ability to generate maximal power is influenced by the type of muscle action involved and, in particular, the time available to develop force, storage and utilization of elastic energy, interactions of contractile and elastic elements, potentiation of contractile and elastic filaments as well as stretch reflexes. Furthermore, maximal power production is influenced by morphological factors including fibre type contribution to whole muscle area, muscle architectural features and tendon properties as well as neural factors including motor unit recruitment, firing frequency, synchronization and inter-muscular coordination. In addition, acute changes in the muscle environment (i.e. alterations resulting from fatigue, changes in hormone milieu and muscle temperature) impact the ability to generate maximal power. Resistance training has been shown to impact each of these neuromuscular factors in quite specific ways. Therefore, an understanding of the biological basis of maximal power production is essential for developing training programmes that effectively enhance maximal power production in the human.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2007
DOI: 10.1519/R-22896.1
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2010
Publisher: Springer Science and Business Media LLC
Date: 05-09-2023
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2012
Publisher: Springer Science and Business Media LLC
Date: 18-11-2010
Publisher: Springer Science and Business Media LLC
Date: 24-02-2023
DOI: 10.1007/S00421-023-05155-X
Abstract: The aim of this study was to examine the goodness of fit, prediction accuracy, and stability of general and in idual relationships between velocity loss and the percentage of completed repetitions out of maximum possible (VL-% repetitions ) in the free-weight back squat exercise. The effects of sex, training status and history, as well as personality traits, on the goodness of fit and the accuracy of these relationships were also investigated. Forty-six resistance-trained people (15 females and 31 males) performed a one-repetition maximum (1RM) test, and two repetitions to failure (RTF) tests, 72 h apart. RTF tests were performed with 70, 80, and 90% of 1RM with 10 min inter-set rest. The findings question the utility of using general and in idual VL-% repetitions relationships to prescribe training volume with free-weight back squats as (1) the agreement in the % repetitions completed until reaching a given velocity loss threshold across two consecutive testing sessions was unacceptable, regardless of the load used and (2) the ability of general and in idual VL-% repetitions relationships to predict % repetitions in a subsequent testing session were poor (absolute errors 10%). Sex, training status and history, and personality traits did not affect the goodness of fit of general and in idual VL-% repetitions relationships or their prediction accuracy, suggesting potential generalisability of those findings among resistance-trained populations. VL-% repetitions relationships do not seem to provide any additional benefits compared to costless, traditional methods and hence should not be used for monitoring and prescribing resistance training with a free-weight back squat exercise.
Publisher: BMJ
Date: 19-08-2011
Abstract: the objectives of this study were to investigate children's physical activity patterns to gain comparisons between home and school and to determine whether the current physical activity guidelines of 60 min of moderate to vigorous physical activity (MVPA) daily were being met. participants were recruited from two New Zealand primary schools (60 children, mean age (SD) 8.3 (0.7) years). Physical activity was measured for seven consecutive days using Actigraph accelerometers. Total activity and average counts were determined for school playtime, after school and weekends. Differences between average counts for these intervals were compared using the t statistic. Time and percentage of time spent were categorised into the activity thresholds: sedentary ( 5200). Total activity for each day was also determined. no child met the recommended 60 min of MVPA daily during the investigation. Compared to school playtime, activity counts were lower by 36% (CI 25% to 45.5%, p<0.001, effect size (ES)=-1.29) after school, 50.1% (CI 37% to 60.5%, p<0.001, ES=-2.01) on Saturday and 57.4% (CI 46.3% to 66.3%, p<0.001, ES=-2.47) on Sunday. Mean results showed children spent 91-96% of their time engaged in light or sedentary activities. Even during school playtime, where the children were most active, only 8 of 80 min were spent engaged in MVPA. this study found activity levels were considerably lower than the recommended guidelines, and children were more active during school playtime compared to after school and weekends.
Publisher: Springer Science and Business Media LLC
Date: 16-02-2001
Abstract: The purpose of this investigation was to assess the myosin heavy chain (MHC) expression in the vastus lateralis muscle from elderly men and women, and to determine whether heavy resistance training influences its expression. Twenty healthy, mildly physically active subjects gave their informed consent to participate in the study. The experimental group consisted of seven men and seven women [mean (SD) age 65.5 (4.1) years] and the control group consisted of three men and three women [mean (SD) age 62.3 (3.6) years]. The 6-month resistance training program was ided into two phases with weeks 1-12 consisting of high-intensity resistance training, and weeks 13-24 involving power training. Muscle biopsy s les were taken from the vastus lateralis muscle at week 0 and week 24 using the needle biopsy technique. The male and female experimental groups both exhibited a significant decrease (P < or = 0.05) in the percentage of MHC IIb, while the experimental female group also demonstrated a significant increase (P < or = 0.05) in the expression of MHC IIa, after 24 weeks of heavy resistance training. There was no change in MHC expression within the control group. The male [130.4 (25.3) kg vs 171.1 (30.5) kg] and female [58.2 (8.3) kg vs 77.9 (11.1) kg] experimental groups exhibited a significant increase (P < or = 0.05) in the maximal strength values for the 1 repetition maximum (1RM) squat exercise. The control group showed no change in strength for the 1RM squat exercise for either the male [115.8 (35.10 kg vs 123.8 (47.2) kg] or female [57.5 (99.0) kg vs 58.3 (2.9) kg] groups. The results clearly show that elderly subjects undergoing heavy resistance training have the ability to produce a similar shift in the expression of MHC isoforms from MHC IIb to MHC IIa, as has been shown to occur in younger subjects. This highlights the plasticity of human skeletal muscle in response to heavy resistance training, even at older ages.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2010
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2009
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.HUMOV.2016.03.005
Abstract: This study assessed reliability of discrete ground reaction force (GRF) variables over multiple pitching trials, investigated the relationships between discrete GRF variables and pitch velocity (PV) and assessed the variability of the "force signature" or continuous force-time curve during the pitching motion of windmill softball pitchers. Intraclass correlation coefficient (ICC) for all discrete variables was high (0.86-0.99) while the coefficient of variance (CV) was low (1.4-5.2%). Two discrete variables were significantly correlated to PV second vertical peak force (r(5)=0.81, p=0.03) and time between peak forces (r(5)=-0.79 p=0.03). High ICCs and low CVs support the reliability of discrete GRF and PV variables over multiple trials and significant correlations indicate there is a relationship between the ability to produce force and the timing of this force production with PV. The mean of all pitchers' curve-average standard deviation of their continuous force-time curves demonstrated low variability (CV=4.4%) indicating a repeatable and identifiable "force signature" pattern during this motion. As such, the continuous force-time curve in addition to discrete GRF variables should be examined in future research as a potential method to monitor or explain changes in pitching performance.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2013
Publisher: Springer Science and Business Media LLC
Date: 02-2011
DOI: 10.2165/11538500-000000000-00000
Abstract: This series of reviews focuses on the most important neuromuscular function in many sport performances: the ability to generate maximal muscular power. Part 1, published in an earlier issue of Sports Medicine, focused on the factors that affect maximal power production while part 2 explores the practical application of these findings by reviewing the scientific literature relevant to the development of training programmes that most effectively enhance maximal power production. The ability to generate maximal power during complex motor skills is of paramount importance to successful athletic performance across many sports. A crucial issue faced by scientists and coaches is the development of effective and efficient training programmes that improve maximal power production in dynamic, multi-joint movements. Such training is referred to as 'power training' for the purposes of this review. Although further research is required in order to gain a deeper understanding of the optimal training techniques for maximizing power in complex, sports-specific movements and the precise mechanisms underlying adaptation, several key conclusions can be drawn from this review. First, a fundamental relationship exists between strength and power, which dictates that an in idual cannot possess a high level of power without first being relatively strong. Thus, enhancing and maintaining maximal strength is essential when considering the long-term development of power. Second, consideration of movement pattern, load and velocity specificity is essential when designing power training programmes. Ballistic, plyometric and weightlifting exercises can be used effectively as primary exercises within a power training programme that enhances maximal power. The loads applied to these exercises will depend on the specific requirements of each particular sport and the type of movement being trained. The use of ballistic exercises with loads ranging from 0% to 50% of one-repetition maximum (1RM) and/or weightlifting exercises performed with loads ranging from 50% to 90% of 1RM appears to be the most potent loading stimulus for improving maximal power in complex movements. Furthermore, plyometric exercises should involve stretch rates as well as stretch loads that are similar to those encountered in each specific sport and involve little to no external resistance. These loading conditions allow for superior transfer to performance because they require similar movement velocities to those typically encountered in sport. Third, it is vital to consider the in idual athlete's window of adaptation (i.e. the magnitude of potential for improvement) for each neuromuscular factor contributing to maximal power production when developing an effective and efficient power training programme. A training programme that focuses on the least developed factor contributing to maximal power will prompt the greatest neuromuscular adaptations and therefore result in superior performance improvements for that in idual. Finally, a key consideration for the long-term development of an athlete's maximal power production capacity is the need for an integration of numerous power training techniques. This integration allows for variation within power meso-/micro-cycles while still maintaining specificity, which is theorized to lead to the greatest long-term improvement in maximal power.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2010
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2006
DOI: 10.1519/R-19165.1
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2005
DOI: 10.1519/14263.1
Abstract: We investigated the effect of "psyching-up" on force production during the bench press. Twelve men (mean age +/- SD: 27.4 +/- 11.2 years) and 8 women (20.9 +/- 2.5 years) with strength-training experience performed 5 bench press repetitions on a modified Biodex isokinetic dynamometer during 3 interventions. The interventions were counterbalanced and included a free-choice psych-up, a cognitive distraction, and an attention-placebo. Peak force recorded after psyching-up (mean +/- SD: 764 +/- 269 N.m) was significantly different from both distraction (703 +/- 282 N.m, p = 0.003) and attention-placebo (708 +/- 248 N.m, p = 0.01). The mean percentage increase in peak force from distraction to psyching-up was 11.8% (6 to 18%, 95% confidence interval [CI]) and 8.1% from placebo to psyching-up (3 to 13%, 95% CI). The results of the present study indicate that psyching-up may increase force production during the bench press exercise in participants with at least 1 year strength-training experience.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2003
DOI: 10.1519/1533-4287(2003)017<0645:EOERTO>2.0.CO;2
Abstract: The purpose of this investigation was to evaluate changes in myosin heavy chain (MyHC) and titin isoforms after using various loads during explosive jump squat training. Twenty-four male athletic subjects were recruited for this study. Two experimental groups performed 8-weeks of jump squats using either 30% (n = 9) or 80% (n = 9) of their previously determined 1 repetition maximum. A third group served as controls (n = 6). Muscle biopsies were obtained before and after 8 weeks from vastus lateralis. The analysis of titin within these subjects confirmed that human skeletal muscle contains 2 isoforms of titin. There was no significant group x time interaction for MyHC or titin isoform expression. The data from this investigation indicates that a relatively short period of explosive resistance training results in negligible changes in the expression of MyHC or titin isoforms.
Publisher: Elsevier BV
Date: 12-2000
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2008
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.JSAMS.2016.08.011
Abstract: The primary objective of this meta-analysis was to compare countermovement jump (CMJ) performance in studies that reported the highest value as opposed to average value for the purposes of monitoring neuromuscular status (i.e., fatigue and supercompensation). The secondary aim was to determine the sensitivity of the dependent variables. Systematic review with meta-analysis. The meta-analysis was conducted on the highest or average of a number of CMJ variables. Multiple literature searches were undertaken in Pubmed, Scopus, and Web of Science to identify articles utilizing CMJ to monitor training status. Effect sizes (ES) with 95% confidence interval (95% CI) were calculated using the mean and standard deviation of the pre- and post-testing data. The coefficient of variation (CV) with 95% CI was also calculated to assess the level of instability of each variable. Heterogeneity was assessed using a random-effects model. 151 articles were included providing a total of 531 ESs for the meta-analyses 85.4% of articles used highest CMJ height, 13.2% used average and 1.3% used both when reporting changes in CMJ performance. Based on the meta-analysis, average CMJ height was more sensitive than highest CMJ height in detecting CMJ fatigue and supercompensation. Furthermore, other CMJ variables such as peak power, mean power, peak velocity, peak force, mean impulse, and power were sensitive in tracking the supercompensation effects of training. The average CMJ height was more sensitive than highest CMJ height in monitoring neuromuscular status however, further investigation is needed to determine the sensitivity of other CMJ performance variables.
Publisher: Springer Science and Business Media LLC
Date: 02-05-2023
DOI: 10.1038/S41598-023-34416-0
Abstract: This study examined the reproducibility of GymAware, PUSH2 and Vmaxpro velocity monitoring devices during resistance training (RT). The sensitivity of these devices to detect the smallest changes in velocity that correspond to true changes in RT performance was also investigated. Fifty-one resistance-trained men and women performed an incremental loading (1RM) test, and two repetitions to failure tests with different loads, 72 h apart. During all repetitions, mean velocity (MV) and peak velocity (PV) were simultaneously recorded by two devices of each brand. Overall, GymAware was the most reliable and sensitive device for detecting the smallest changes in RT performance, regardless of the velocity metric used. Vmaxpro can be considered as an equivalent, cheaper alternative to GymAware for RT monitoring and prescription, but only if the MV metric is used. Caution should be exercised when using PUSH2 in practice due to their comparatively higher, unacceptable measurement error and generally low sensitivity to detect changes in RT performance. Collectively, these findings support the use of MV and PV from GymAware and MV from Vmaxpro devices for RT monitoring and prescription due to their low magnitudes of error thus, allowing for the detection of meaningful changes in neuromuscular status and functional performance during RT.
Publisher: Springer Science and Business Media LLC
Date: 27-06-2008
DOI: 10.1007/S00421-008-0806-7
Abstract: Controversy exists concerning the susceptibility of elderly in iduals to eccentric exercise-induced muscle damage. This study investigated the hypothesis that muscle damage induced by fast maximal lengthening contractions would be greater for old than young men. Ten old (64 +/- 4 years) and young (25 +/- 6 years) men performed 30 maximal voluntary lengthening contractions of the elbow flexors at an angular velocity of 210 degrees s(-1). Prior to exercise, no significant differences were evident between groups for criterion measures. A significant (P < 0.05) group x time interaction was found only for isometric strength and muscle soreness with the old group showing significantly slower recovery of strength and less development of soreness compared with the young group. These results did not support the hypothesis that old men would be more susceptible to muscle damage, but confirmed a previous study reporting that recovery of muscle strength was slower for old than young in iduals.
Publisher: Springer Science and Business Media LLC
Date: 11-07-2022
DOI: 10.1007/S40279-022-01715-X
Abstract: The primary aim of this narrative review was to outline the historical genesis of resistance training strategies that incorporate high-load, low-velocity exercises and low-load, high-velocity exercises in the same training session allowing for different "exercise sequences" to be simultaneously implemented. Discrepancies between scientific works and the terminology used within contemporary sport science publications are identified. Upon review of the literature, we propose "complex training" to be considered an umbrella term with 4 different implementations, generally used to indicate a method in which movement velocity or load is altered between sets and/or exercises within the same session with the aim of improving slow and fast force expression. We propose the following terminology for said implementations: contrast training-exercise sequence with alternating high-load and low-load (higher-velocity) exercises in a set-by-set fashion within the same session (corresponding with 'contrast pairs' and 'intra-contrast rest') descending training-several sets of high-load (e.g., back squat) exercises completed before the execution of several sets of low-load, higher-velocity (e.g., vertical jump) exercises within the same session ascending training-several sets of low-load, higher-velocity exercises completed before several sets of high-load exercises within the same session and French contrast training-subset of contrast training in which a series of exercises are performed in sequence within a single session: heavy compound exercise, plyometric exercise, light-to-moderate load compound exercise that maximises movement speed (i.e., external power), and a plyometric exercise (often assisted). Finally, practical applications and training considerations are presented.
Publisher: Springer Science and Business Media LLC
Date: 12-11-2010
DOI: 10.1007/S00421-009-1278-0
Abstract: This study compared the first and second exercise bouts consisting of electrically evoked isometric contractions for muscle damage profile. Nine healthy men (31 +/- 4 years) had two electrical muscle stimulation (EMS) bouts separated by 2 weeks. The knee extensors of one leg were stimulated by biphasic rectangular pulses (75 Hz, 400 mus, on-off ratio 5-15 s) at the knee joint angle of 100 degrees (0 degrees , full extension) to induce 40 isometric contractions, while the current litude was increased to maintain maximal force generation. Maximal voluntary isometric contraction (MVC) torque of the knee extensors at 100 degrees , muscle soreness, pressure pain threshold and plasma creatine kinase (CK) activity were used as indirect markers of muscle damage, and measured before and 1, 24, 48, 72 and 96 h after EMS bout, and the changes over time were compared between bouts. The torque produced during exercise was approximately 30% of MVC, and no significant difference between bouts was evident for the changes in peak and average torque over 40 contractions. MVC decreased significantly (P < 0.05) by 26% immediately and 1 h after both bouts, but the recovery was significantly (P < 0.05) faster after the second bout (100% at 96 h) compared with the first bout (81% at 96 h). Development of muscle soreness and tenderness, and increases in plasma CK activity were significantly (P < 0.05) smaller after the second than the first bout. These results show that changes in muscle damage markers were attenuated in the second EMS bout compared with the initial EMS bout.
Publisher: Springer Science and Business Media LLC
Date: 15-06-2019
DOI: 10.1007/S40279-019-01136-3
Abstract: Recent scientific evidence supports the use of a low-volume strength-power 'resistance priming' session prior to sporting competition in an effort to enhance neuromuscular performance. Though research evidence relating to this strategy is presently limited, it has been shown to be effective in improving various measures of neuromuscular performance within 48 h. Post-activation potentiation strategies have previously been shown to enhance strength-power performance within 20 min of completing maximal or near-maximal resistance exercise. Comparably, a delayed potentiation effect has been demonstrated following 'resistance priming' at various times between 1 and 48 h in upper- and lower-body performance measures. This may have significant implications for a range of athletes when preparing for competition. Various exercise protocols have been shown to improve upper- and lower-body neuromuscular performance measures in this period. In particular, high-intensity resistance exercise through high loading (≥ 85% 1 repetition maximum) or ballistic exercise at lower loads appears to be an effective stimulus for this strategy. Although current research has identified the benefits of resistance priming to some physical qualities, many questions remain over the application of this type of session, as well as the effects that it may have on a range of specific sporting activities. The aims of this brief review are to assess the current literature examining the acute effects (1-48 h) of resistance exercise on neuromuscular performance and discuss potential mechanisms of action as well as provide directions for future research.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2017
DOI: 10.1519/JSC.0000000000001739
Abstract: Weiss, KJ, McGuigan, MR, Besier, TF, and Whatman, CS. Application of a simple surveillance method for detecting the prevalence and impact of overuse injuries in professional men's basketball. J Strength Cond Res 31(10): 2734–2739, 2017—The aim of this study was to use the Oslo Sports Trauma Research Center (OSTRC) Overuse Injury Questionnaire to record overuse injuries over a single season for a men's professional basketball team to (a) assess the prevalence and severity of overuse injuries and (b) determine the efficacy of this method in identifying overuse injuries in comparison with the team physiotherapist's detection of these injuries. Thirteen athletes from a men's professional basketball team participated in this study. The self-reported, OSTRC injury questionnaire was used to record overuse conditions of the ankle, knee, and lower back over an entire 24-week season. Standard time-loss injury registration methods were also used to record overuse conditions by the physiotherapist. Overuse injury rates per 1,000 hours of athlete exposure and average weekly prevalence of overuse injuries were calculated using the results of the questionnaire. A total of 183 overuse conditions were identified by the questionnaire, whereas only 28 overuse conditions were identified by the physiotherapist. The team's average weekly prevalence of all overuse conditions was 63% (95% confidence interval [CI]: 60–66), with the highest prevalence of injury affecting the lower back (25.9% [95% CI: 19.7–32.1]). The overuse injury rate per 1,000 hours of athlete exposure was 6.4. The OSTRC overuse injury questionnaire captures many more overuse injuries in basketball than standard time-loss methods. The prevalence of lower back injuries is higher than that previously reported in basketball. This additional method of overuse injury surveillance may more accurately quantify the overuse injury problem in basketball and aid earlier intervention and management of these conditions.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2013
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2006
DOI: 10.1519/R-18300.1
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2009
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2009
DOI: 10.1519/JSC.0B013E3181876A56
Abstract: The purpose of this study was to investigate the effect of an 8-week resistance training program on children who were overweight or obese. Forty-eight children (n = 26 girls and 22 boys mean age = 9.7 years) participated in an 8-week undulating periodized resistance training program for 3 d x wk-1. Measures of body composition via dual-energy X-ray absorptiometry, anthropometry, strength, and power were made before and after the training intervention. There was a significant decrease in absolute percent body fat of 2.6%(p = 0.003) and a significant increase in lean body mass of 5.3% (p = 0.07). There were no significant changes in height, weight, body mass index, total fat mass, or bone mineral content. There were significant increases in 1-repetition maximum squat (74%), number of push-ups (85%), countermovement jump height (8%), static jump height (4%), and power (16%). These results demonstrate that the resistance training program implemented produces significant changes in body composition and strength and power measures, as well as being well tolerated by the participants. An undulating periodized program provides variation and significantly increases lean body mass, decreases percent body fat, and increases strength and power in children who are overweight and obese.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2010
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2011
Publisher: Elsevier BV
Date: 2010
Publisher: Elsevier BV
Date: 03-2006
Publisher: Springer Science and Business Media LLC
Date: 17-07-2008
Abstract: This study examined the effect of 20 weeks resistance training on a range of serum hormones and inflammatory markers at rest, and following acute bouts of exercise in prostate cancer patients undergoing androgen deprivation. Ten patients exercised twice weekly at high intensity for several upper and lower-body muscle groups. Neither testosterone nor prostate-specific antigen changed at rest or following an acute bout of exercise. However, serum growth hormone (GH), dehydroepiandrosterone (DHEA), interleukin-6, tumor necrosis factor-alpha and differential blood leukocyte counts increased (P < 0.05) following acute exercise. Resistance exercise does not appear to compromise testosterone suppression, and acute elevations in serum GH and DHEA may partly underlie improvements observed in physical function.
Publisher: American Physiological Society
Date: 09-2010
DOI: 10.1152/JAPPLPHYSIOL.00189.2010
Abstract: This study compared alternating current and pulsed current electrical muscle stimulation (EMS) for torque output, skin temperature ( T sk ), blood lactate and hormonal responses, and skeletal muscle damage markers. Twelve healthy men (23–48 yr) received alternating current EMS (2.5 kHz delivered at 75 Hz, 400 μs) for the knee extensors of one leg and pulsed current (75 Hz, 400 μs) for the other leg to induce 40 isometric contractions (on-off ratio 5–15 s) at the knee joint angle of 100° (0°: full extension). The use of the legs for each condition was counterbalanced among subjects, and the two EMS bouts were separated by 2 wk. The current litude was consistently increased to maximally tolerable level, and the torque and perceived intensity were recorded over 40 isometric contractions. T sk of the stimulated and contralateral knee extensors were measured before, during, and for 30 min after EMS. Blood lactate, growth hormone, testosterone, insulin-like growth factor 1, testosterone, and cortisol were measured before, during, and for 45 min following EMS. Muscle damage markers included maximal voluntary isometric contraction torque, muscle soreness with a 100-mm visual analog scale, and plasma creatine kinase (CK) activity, which were measured before and 1, 24, 48, 72, and 96 h after EMS. No significant differences in the torque induced during stimulation (∼30% maximal voluntary isometric contraction) and perceived intensity were found, and changes in T sk , blood lactate, and hormones were not significantly different between conditions. However, all of the measures showed significant ( P 0.05) changes from baseline values. Skeletal muscle damage was evidenced by prolonged strength loss, development of muscle soreness, and increases in plasma CK activity however, the changes in the variables were not significantly different between conditions. It is concluded that acute effects of alternating and pulsed current EMS on the stimulated muscles are similar.
Publisher: Springer Science and Business Media LLC
Date: 08-09-2020
DOI: 10.1007/S40279-020-01344-2
Abstract: The alteration of in idual sets during resistance training (RT) is often used to allow for greater velocity and power outputs, reduce metabolite accumulation such as lactate and also reduce perceived exertion which can ultimately affect the resultant training adaptations. However, there are inconsistencies in the current body of evidence regarding the magnitude of the effects of alternative set structures (i.e., cluster sets and rest redistribution) on these acute mechanical, metabolic, and perceptual responses during and after RT. This study aimed to systematically review and meta-analyse current evidence on the differences between traditional and alternative (cluster and rest redistribution) set structures on acute mechanical, metabolic, and perceptual responses during and after RT, and to discuss potential reasons for the disparities noted in the literature. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and five databases were searched until June 2019. Studies were included when they were written in English and compared at least one acute mechanical, metabolic, or perceptual response between traditional, cluster or traditional and rest redistribution set structures in healthy adults. Random-effects meta-analyses and meta-regressions were performed where possible. Thirty-two studies were included. Pooled results revealed that alternative set structures allowed for greater absolute mean [standardized mean difference (SMD) = 0.60] and peak velocity (SMD = 0.41), and mean (SMD = 0.33) and peak power (SMD = 0.38) during RT. In addition, alternative set structures were also highly effective at mitigating a decline in velocity and power variables during (SMD = 0.83-1.97) and after RT (SMD = 0.58) as well as reducing lactate accumulation (SMD = 1.61) and perceived exertion (SMD = 0.81). These effects of alternative set structures on velocity and power decline and maintenance during RT were considerably larger than for absolute velocity and power variables. Sub-group analyses controlling for each alternative set structure independently showed that cluster sets were generally more effective than rest redistribution in alleviating mechanical, metabolic, and perceptual markers of fatigue. Alternative set structures can reduce mechanical fatigue, perceptual exertion, and metabolic stress during and after RT. However, fundamental differences in the amount of total rest time results in cluster sets generally being more effective than rest redistribution in alleviating fatigue-induced changes during RT, which highlights the importance of classifying them independently in research and in practice. Additionally, absolute values (i.e., mean session velocity or power), as well as decline and maintenance of the mechanical outcomes during RT, and residual mechanical fatigue after RT, are all affected differently by alternative set structures, suggesting that these variables may provide distinct information that can inform future training decisions. The original protocol was prospectively registered (CRD42019138954) with the PROSPERO (International Prospective Register of Systematic Reviews).
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2009
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.JSAMS.2019.09.010
Abstract: Recent research has revealed that low volume resistance 'priming' exercise may improve neuromuscular performance when completed within 48h before competition. The aim of this study was to investigate the current prevalence and application of this strategy by practitioners in sport. This study surveyed practitioners who were currently programming and/or prescribing resistance training programs for high performance athletes. Sixty-nine practitioners completed the online survey relating to their perceptions of resistance priming exercise strategies and the training methods prescribed in the days prior to competition. Fifty-one percent of respondents currently prescribed priming exercise. Of the practitioners who prescribed this strategy, most respondents (59%) prescribed this session within 8h of competition. Sessions typically included 2-3 upper body and lower body exercises (mean=2.5±0.7 and 2.1±0.6 respectively), usually involving both loaded and unloaded activities. Large variations in exercise selection were reported, however, unloaded jumps (87%), loaded jumps (60%) and bench press (56%) were commonly prescribed. A low volume of sets (mean=2.8±0.9) and repetitions (mean=3.8±1.3) were used during these sessions. Lastly, various resistance loading strategies were prescribed, ranging from unloaded activities to heavy loaded exercises performed at ≥85% 1RM. Priming exercise is currently prescribed by many practitioners to prepare athletes for competition. A wide range of priming exercise methods are used, despite limited evidence supporting these methods. Future research should examine the effects of the various priming methods which are currently applied in practice.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2006
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2016
DOI: 10.1519/JSC.0000000000001292
Abstract: Pritchard, HJ, Tod, DA, Barnes, MJ, Keogh, JW, and McGuigan, MR. Tapering practices of New Zealand's elite raw powerlifters. J Strength Cond Res 30(7): 1796–1804, 2016—The major aim of this study was to determine tapering strategies of elite powerlifters. Eleven New Zealand powerlifters (28.4 ± 7.0 years, best Wilks score of 431.9 ± 43.9 points) classified as elite were interviewed, using semistructured interviews, about their tapering strategies. Interviews were transcribed verbatim and content analyzed. Total training volume peaked 5.2 ± 1.7 weeks from competition while average training intensity (of 1 repetition maximum) peaked 1.9 ± 0.8 weeks from competition. During tapering, volume was reduced by 58.9 ± 8.4% while intensity was maintained (or slightly reduced) and the final weight training session was performed 3.7 ± 1.6 days out from competition. Participants generally stated that tapering was performed to achieve full recovery that accessory work was removed around 2 weeks out from competition and deadlifting takes longer to recover from than other lifts. Typically participants stated that trial and error, and changes based on “feel” were the sources of tapering strategies equipment used and movements performed during tapering are the same as in competition nutrition was manipulated during the taper (for weight cutting or performance aims) and poor tapering occurred when too long (1 week or more) was taken off training. These results suggest that athletes may benefit from continuing to strength train before important events with reduced volume and maintained intensity. Only exercises that directly assist sports performance should remain in the strength program during tapering, to assist with reductions in fatigue while maintaining/improving strength expression and performance.
Publisher: Springer Science and Business Media LLC
Date: 27-10-2011
DOI: 10.1007/S00421-010-1699-9
Abstract: This study compared between alternating and pulsed current electrical muscle stimulation (EMS) for muscle oxygenation and blood volume during isometric contractions. Nine healthy men (23-48 years) received alternating current EMS (2500 Hz) modulated at 75 Hz on the knee extensors of one leg, and pulsed current EMS (75 Hz) for the other leg separated by 2 weeks in a randomised, counter-balanced order. Pulse duration (400 μs), on-off ratio (5-15 s) and other stimulation parameters were matched between conditions and 30 isometric contractions were induced at the knee joint angle of 100° (0° full extension). Changes in tissue oxygenation index (∆TOI) and total hemoglobin volume (∆tHb) of vastus lateralis and medialis muscles over 30 contractions were assessed by a near-infrared spectroscopy, and were compared between conditions by a two-way repeated measures ANOVA. Peak torque produced during EMS increased over 30 contractions in response to the increase in the stimulation intensity for pulsed current, but not for the alternating current EMS. The torque during each isometric contraction was less stable in alternating than pulsed current EMS. The changes in ∆TOI litude during relaxation phases and ∆tHb litude were not significantly different between conditions. However, the decreases in ∆TOI litude during contraction phases from baseline were significantly (P < 0.05) greater for the pulsed current than alternating current from the 18th contraction (-15.6 ± 2.3 vs. -8.9 ± 1.8%) to 30th contraction (-10.7 ± 1.8 vs. -4.8 ± 1.5%). These results suggest that the muscles were less activated in the alternating current EMS when compared with the pulsed current EMS.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2009
DOI: 10.1519/JSC.0B013E31818753CA
Abstract: Measuring and tracking performance variables such as peak power output is essential for assessing the effects of training and for informing adjustments to optimize program design. The purpose of this study was to track the long-term changes in muscular power, velocity, and jump height of elite Australian Rules Football (ARF) players during a 3-year period. Twelve members of an ARF team were tracked during the study. The physical characteristics of the subjects were age, 25.3 6 2.8 years body mass, 93.0 6 6.8 kg and height, 192 6 6 cm. The subjects performed unweighted and weighted (40 kg) countermovement jumps (CMJ) and static jumps (SJ). Peak power, jump height, and bar velocity were determined using a force plate and position transducer.Measures of peak power output during both the CMJ and SJ indicated significant (p# 0.001) increases of 13% (effect size [ES] = 0.70) and 17% (ES = 1.77), respectively, during the course of the tracking period. There was also a significant 9% (ES = 0.71) increase in CMJ40 peak power. The subjects' CMJ peak velocity improved by 10.7% (ES = 0.34), and SJ peak velocity improved by 12.6% (ES = 0.37). The data from this study show that elite-level ARF players can continue to increase muscular power and velocity. This information is of interest to strength and conditioning coaches who are interested in improving power performance of their athletes for a long-term period.
Location: United States of America
Location: United States of America
No related grants have been discovered for Michael McGuigan.