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1.
Int J Sports Med ; 42(4): 300-306, 2021 Apr.
Article in English | MEDLINE | ID: mdl-33075832

ABSTRACT

Training load monitoring is a core aspect of modern-day sport science practice. Collecting, cleaning, analysing, interpreting, and disseminating load data is usually undertaken with a view to improve player performance and/or manage injury risk. To target these outcomes, practitioners attempt to optimise load at different stages throughout the training process, like adjusting individual sessions, planning day-to-day, periodising the season, and managing athletes with a long-term view. With greater investment in training load monitoring comes greater expectations, as stakeholders count on practitioners to transform data into informed, meaningful decisions. In this editorial we highlight how training load monitoring has many potential applications and cannot be simply reduced to one metric and/or calculation. With experience across a variety of sporting backgrounds, this editorial details the challenges and contextual factors that must be considered when interpreting such data. It further demonstrates the need for those working with athletes to develop strong communication channels with all stakeholders in the decision-making process. Importantly, this editorial highlights the complexity associated with using training load for managing injury risk and explores the potential for framing training load with a performance and training progression mindset.


Subject(s)
Athletes , Athletic Performance , Physical Conditioning, Human/methods , Sports/physiology , Athletic Injuries/prevention & control , Communication , Data Collection/methods , Data Interpretation, Statistical , Decision Making , Humans , Risk Management/methods , Stakeholder Participation , Workload/statistics & numerical data
2.
Int J Sport Nutr Exerc Metab ; 29(1): 46-50, 2019 Jan 01.
Article in English | MEDLINE | ID: mdl-29893591

ABSTRACT

This field-based observational study was designed to examine the intraindividual variation of first morning body mass and urine specific gravity (Usg) in male hockey players (n = 22) during a 10-day training camp. It was also designed to evaluate the prevalence and interrelationship of morning hypohydration and postmatch dehydration using Usg and changes in body mass, respectively. Body mass and Usg were measured upon waking; body mass was also measured before and after matches. Individual means, SD, and coefficient of variation (CV) were calculated for morning body mass and Usg using 3, 6, and 8 days. Daily prevalence for euhydration and postmatch dehydration using morning Usg (<1.020) and changes in body mass (>-2%), respectively, were determined. Measurement of morning body mass and Usg for 3 days had low variability (CV < 1%) with no improvement at 6 or 8 days. Between 36% and 73% of players were considered euhydrated based on morning Usg. Postmatch body mass was reduced >1% in 50-85% of players, with up to 40% experiencing changes >-2%. Postmatch changes in body mass were unrelated to Usg the subsequent morning. These outcomes can be helpful in establishing criteria for detecting meaningful changes in morning body mass and Usg in similar settings, helping to monitor hydration status in elite male athletes. Despite ample fluid availability and consumption, many players experienced hypohydration and dehydration during the camp, indicating that careful monitoring and an individual fluid replacement approach are warranted in these environments.

3.
J Med Syst ; 43(12): 328, 2019 Oct 27.
Article in English | MEDLINE | ID: mdl-31655934

ABSTRACT

The purpose of this study was to examine the intra-individual variation of heart rate variability (HRV) and heart rate using an orthostatic challenge in elite male athletes during a training camp. Heart rate (variability) was measured upon waking. Log-transformed HRV metrics were evaluated in three segments (first min discarded for stabilization): 0-3 min supine, 3-6 min supine, and standing. Heart rate was assessed while supine, 15 s after standing and average final 30 s standing (Rusko protocol). A RM-ANOVA compared intra-individual means, standard deviations (SD) and coefficients of variation (CV%) for HRV and heart rate. The intraclass correlation coefficient (ICC) and standard error of measurement (SEmeas) were used for relative and absolute reliability, respectively. Time and frequency domain HRV metrics had low variation (CV% <8.5%; SEmeas% ≤4.0%) for 0-3 min supine which was not improved during 3-6 min. Standing HRV had lower ICC and higher SEmeas than supine values. Variability and reliability outcomes for heart rate were comparable to log-transformed HRV metrics. This study uniquely describes the intra-individual variation of HRV metrics during an orthostatic challenge and demonstrated low variability in this cohort of elite male athletes. These data can be helpful for identifying when true individual changes occur for the autonomic nervous system indices in supine and standing positions.


Subject(s)
Autonomic Nervous System/physiology , Heart Rate/physiology , Hockey , Posture/physiology , Adult , Athletes , Humans , Male , Reproducibility of Results , Young Adult
4.
Int J Sport Nutr Exerc Metab ; 26(4): 363-9, 2016 Aug.
Article in English | MEDLINE | ID: mdl-26696652

ABSTRACT

This observational case study examined the association of inter- and intraday energy intake and exercise energy expenditure with bone health, menstrual status and hematological factors in a female triathlete. The study spanned 7 months whereby energy intake and exercise energy expenditure were monitored three times (13 d); 16 blood samples were taken, urinary hormones were assessed for 3 months, and bone mineral density was measured twice. Energy availability tended to be sustained below 30 kcal/kg FFM/d and intraday energy intake patterns were often "back-loaded" with approximately 46% of energy consumed after 6 p.m. Most triiodothyronine values were low (1.1-1.2nmol/L) and supportive of reduced energy availability. The athlete had suppressed estradiol (105.1 ± 71.7pmol/L) and progesterone (1.79 ±1.19nmol/L) concentrations as well as urinary sex-steroid metabolites during the entire monitoring period. Lumbar spine (L1-L4) bone mineral density was low (age-matched Z-score -1.4 to -1.5). Despite these health related maladies the athlete was able to perform typical weekly training loads (swim: 30-40 km, bike: 120-300 km, run 45-70 km) and was competitive as indicated by her continued improvement in ITU World Ranking during and beyond the assessment period. There is a delicate balance between health and performance that can become blurred especially for endurance athletes. Education (athletes, coaches, parents) and continued monitoring of specific indicators will enable evidence-based recommendations to be provided and help reduced the risk of health related issues while maximizing performance gains. Future research needs to longitudinally examine how performance on standardized tests in each discipline (e.g., 800-m swim, 20-km time trial, 5-km run) is impacted when aspects of the female athlete triad are present.


Subject(s)
Athletes , Energy Intake , Estradiol/urine , Lumbar Vertebrae/physiology , Menstruation/physiology , Progesterone/urine , Body Mass Index , Body Weight , Bone Density , Dietary Carbohydrates/administration & dosage , Dietary Fats/administration & dosage , Dietary Proteins/administration & dosage , Energy Metabolism , Female , Female Athlete Triad Syndrome/diagnosis , Ferritins/blood , Hematocrit , Hemoglobins/metabolism , Humans , Swimming , Transferrin/metabolism , Young Adult
6.
J Sports Sci ; 30(12): 1259-65, 2012.
Article in English | MEDLINE | ID: mdl-22897497

ABSTRACT

The aim of this study was to determine sprint profiles of professional female soccer players and evaluate how various speed thresholds impact those outcomes. Seventy-one professional players competing in full matches were assessed repeatedly during 12 regular season matches using a Global Positioning System (GPS). Locomotion ≥18 km · h⁻¹ was defined as sprinting and each event was classified into: Zone 1: 18.0-20.9 km· h⁻¹; Zone 2: 21.0-22.9 km · h⁻¹; Zone 3: 23.0-24.9 km · h⁻¹ and Zone 4: >25 km · h⁻¹. Outcomes included: duration (s), distance (m), maximum speed (km · h⁻¹), duration since previous sprint (min) and proportion of total sprint distance. In total 5,019 events were analysed from 139 player-matches. Mean sprint duration, distance, maximum speed and time between sprints were 2.3 ± 1.5 s, 15.1 ± 9.4 m, 21.8 ± 2.3 km· h⁻¹, and 2.5 ± 2.5 min, respectively. Mean sprint distances were 657 ± 157, 447 ± 185, and 545 ± 217 m for forwards, midfielders and defenders, respectively (P ≤ 0.046). Midfielders had shorter sprint duration (P = 0.023), distance (P ≤ 0.003) and maximum speed (P < 0.001), whereas forwards performed more sprints per match (43 ± 10) than midfielders (31 ± 11) and defenders (36 ± 12) (P ≤ 0.016). Forty-five percent, 29%, 15%, and 11% of sprints occurred in sprint Zones 1, 2, 3 and 4, respectively. This group of professional female soccer players covered 5.3 ± 2.0% of total distance ≥18 km · h⁻¹ with positional differences and percent decrements distinct from other previously identified elite players. These data should guide the development of high intensity and sprint thresholds for elite-standard female soccer players.


Subject(s)
Athletic Performance , Competitive Behavior , Physical Endurance , Running , Soccer , Task Performance and Analysis , Female , Humans
7.
Front Sports Act Living ; 3: 629694, 2021.
Article in English | MEDLINE | ID: mdl-34124653

ABSTRACT

The purpose of this study was to compare model estimates of linear sprint mechanical characteristics using timing gates with and without time correction. High-level female soccer players (n = 116) were evaluated on a 35-m linear sprint with splits at 5, 10, 20, 30, and 35 m. A mono-exponential function was used to model sprint mechanical metrics in three ways: without a time correction, with a fixed (+0.3 s) time correction, and with an estimated time correction. Separate repeated-measures ANOVAs compared the sprint parameter estimates between models and also the residuals between models. Differences were identified between all modeled sprint mechanical metrics; however, comparable estimates to the literature occurred when either time correction was used. Bias for both time-corrected models was reduced across all sprint distances compared to the uncorrected model. This study confirms that a time correction is warranted when using timing gates at the start line to model sprint mechanical metrics. However, determining whether fixed or estimated time corrections provide greater accuracy requires further investigation.

8.
Front Sports Act Living ; 3: 634696, 2021.
Article in English | MEDLINE | ID: mdl-33937752

ABSTRACT

Female soccer players are exposed to specific physical demands during matches, which vary according to the standard of play. Existing studies have largely focused on quantifying the distances covered for professional and international level players. This approach is limited in scope regarding the broader aspects around physical demands and is detached from development pathway models. An understanding of the demands across all standards will provide valuable insights about appropriate player development and help ensure physical readiness for the demands of the sport. The aim of this perspective paper is to describe the physical demands experienced during women's soccer matches across the developmental spectrum. A combination of evidence from the literature and data from the author's research (JDV) is presented. Specifically highlighted are the trends for locomotor distances, acceleration and deceleration frequency, and metabolic power metrics for youth (≤U17), college (NCAA/U20), professional (domestic) and international standards of women's soccer. In addition, the changes in match demands between levels of play are used to help illustrate gaps that must be overcome in order to successfully achieve physical readiness to compete at higher levels. The evidence demonstrates the importance of training appropriate attributes to prepare female soccer players who are striving to play at progressively higher standards.

9.
Eur J Sport Sci ; 19(2): 141-146, 2019 Mar.
Article in English | MEDLINE | ID: mdl-29961405

ABSTRACT

The aim of this study was to examine the impact of contextual factors on relative locomotor and metabolic power distances during professional female soccer matches. Twenty-eight players (forwards, n = 4; midfielders, n = 12; defenders, n = 12) that competed in a 90-min home and away match (regular season only). The generalised estimating equations (GEE) was used to evaluate relative locomotor and metabolic power distances for three contextual factors: location (home vs. away), type of turf (natural vs. artificial), and match outcome (win, loss and draw). No differences were observed for home vs. away matches. Moderate-intensity running (20.0 ± 1.0 m min-1 and 16.4 ± 0.9 m min-1), high-intensity running (8.6 ± 0.4 m min-1 and 7.3 ± 0.4 m min-1) and high-metabolic power (16.3 ± 0.5 m min-1 and 14.4 ± 0.5 m min-1) distances were elevated on artificial turf compared to natural grass, respectively. Relative sprint distance was greater during losses compared with draws (4.3 ± 0.4 m min-1 and 3.4 ± 0.3 m min-1). Overall physical demands of professional women's soccer were not impacted by match location. However, the elevation of moderate and high-intensity demands while playing on artificial turf may have implications on match preparations as well as recovery strategies.


Subject(s)
Athletic Performance/physiology , Physical Endurance , Running/physiology , Soccer/physiology , Athletes , Female , Humans
10.
Physiol Behav ; 95(1-2): 48-55, 2008 Sep 03.
Article in English | MEDLINE | ID: mdl-18508099

ABSTRACT

We compared bone mineral density (BMD) and content (BMC), menstrual and metabolic status between physically active women with 1) high cognitive dietary restraint (High-CDR) (score > or = 9, n=38) and Normal-CDR (score<9, n=46) and 2) across quartiles of CDR scores. Eighty-four physically active (500+/-35 min wk(-1)) premenopausal women participated and were categorized according to their CDR score. Primary outcomes included, BMD, BMC, menstrual status, estrone-3-glucuronide (E1G) and pregnanediol-3-glucuronide (PdG) area under the curve (AUC). Secondary outcomes included resting energy expenditure (REE), total triiodothyronine, and ghrelin. Measures of body mass (59.2+/-1.1 vs. 58.5+/-1.0 kg) and percent body fat (24.7+/-1.2 vs. 23.7+/-0.7%) were similar between women with Normal-CDR and High-CDR, however the High-CDR group had lower total body (1.140+/-0.011 vs. 1.179+/-0.010 g cm(-2); p=0.015) and lumbar spine (1.114+/-0.019 vs. 1.223+/-0.022 g cm(-2); p=0.001) BMD. The prevalence of oligo-amenorrhea was higher in the High-CDR group and became increasingly greater across the CDR quartiles. There were no differences in metabolic characteristics between the High-CDR and Normal-CDR groups, however REE and the ratio of measured to predicted REE were lower in the fourth quartile (CDR scores > or = 13) compared to the second and third quartiles. Our results provide evidence that high CDR scores are associated with reduced lumbar spine and total body BMD in physically active premenopausal women. A greater frequency of menstrual disturbances in women with higher CDR scores likely played a role in the reduced total body and lumbar spine BMD.


Subject(s)
Body Composition , Bone Density/physiology , Diet, Reducing/methods , Energy Metabolism/physiology , Menstruation , Absorptiometry, Photon/methods , Adolescent , Adult , Area Under Curve , Body Mass Index , Feeding Behavior/physiology , Female , Ghrelin/metabolism , Humans , Luteinizing Hormone/urine , Nutritional Status , Pregnanediol/analogs & derivatives , Pregnanediol/metabolism , Regression Analysis , Triiodothyronine/metabolism
11.
Contraception ; 77(2): 97-104, 2008 Feb.
Article in English | MEDLINE | ID: mdl-18226672

ABSTRACT

BACKGROUND: We examined the response of bone turnover markers and indices of energy status after 2 weeks of oral contraceptive (OC) therapy in premenopausal women with exercise-associated menstrual disturbances (EAMD). STUDY DESIGN: Six women with EAMD received one 28-day cycle of a triphasic OC containing 180-250 mcg norgestimate/25 mcg ethinyl estradiol (EAMD+OC) and six were controls (EAMD controls). Bone turnover markers amino-terminal propeptide of Type I procollagen and serum carboxy-terminal telopeptides of Type I collagen (PINP and SCTX-I) were assessed at baseline and after 2 weeks of OC therapy (EAMD+OC) or after a 30-day monitoring period (EAMD controls). Total triiodothyronine, resting energy expenditure (REE) and dietary intake were assessed as secondary end points. The absolute and percent changes from baseline in the primary and secondary outcomes were evaluated using an analysis of covariance, adjusting for baseline values of the corresponding outcome. RESULTS: Compared to EAMD controls, a significant change from baseline was observed in the EAMD+OC group for PINP (mean+/-SEM, 9.9+/-6.1 vs. -33.9+/-9.0 mcg/L; p=.005) and SCTX-I (-0.02+/-0.11 vs. -0.25+/-0.07 ng/mL; p=.017), but not osteoprotegerin (-0.53+/-0.22 vs. 0.20+/-0.44 pmol/L; p=.429) after 2 weeks (14.7+/-0.3 days) of OC therapy. Total triiodothyronine levels were elevated in the EAMD+OC group after therapy compared with EAMD controls (19.7+/-4.1 vs. -8.4+/-4.9 ng/dL; p=.002); however, no differences between groups were observed for the changes in REE or dietary intake. CONCLUSION: Our data demonstrate that 2 weeks of low-dose OC therapy rapidly reduced markers of bone resorption and formation, without any significant impact on energy status in women with EAMD.


Subject(s)
Amenorrhea/complications , Bone and Bones/drug effects , Contraceptives, Oral, Combined/administration & dosage , Contraceptives, Oral, Synthetic/administration & dosage , Energy Metabolism/drug effects , Exercise/physiology , Hypothalamic Diseases/complications , Adult , Amenorrhea/metabolism , Biomarkers/blood , Bone Resorption , Bone and Bones/metabolism , Energy Intake/drug effects , Energy Intake/physiology , Energy Metabolism/physiology , Ethinyl Estradiol/administration & dosage , Female , Humans , Hypothalamic Diseases/metabolism , Norgestrel/administration & dosage , Norgestrel/analogs & derivatives , Peptide Fragments/blood , Procollagen/blood , Prospective Studies
12.
J Strength Cond Res ; 22(4): 1147-55, 2008 Jul.
Article in English | MEDLINE | ID: mdl-18545195

ABSTRACT

It is often recommended that in-season training programs aim to maintain muscular strength and power developed during the off-season. However, improvements in performance may be possible with a well-designed training regimen. The purpose of this case report is to describe the changes in physical performance after an in-season training regimen in professional female volleyball players in order to determine whether muscular strength and power might be improved. Apart from normal practice sessions, 10 elite female volleyball players completed 2 training sessions per week, which included both resistance training and plyometric exercises. Over the 12-week season, the athletes performed 3-4 sets of 3-8 repetitions for resistance and plyometric exercises during each training session. All sessions were supervised by one of the investigators as well as by the team head coach. Muscular strength and power were assessed before and after the 12-week training program using 4 repetition maximum bench press and parallel squat tests, an overhead medicine ball throw (BTd), as well as unloaded and loaded countermovement jumps (CMJs). Strength improved by 15% and 11.5% in the bench press and parallel squat, respectively (p < 0.0001). Distance in the BTd improved by 11.8% (p < 0.0001), whereas unloaded and loaded CMJ height increased between 3.8 and 11.2%. The current findings suggest that elite female volleyball players can improve strength and power during the competition season by implementing a well-designed training program that includes both resistance and plyometric exercises.


Subject(s)
Athletic Performance/physiology , Muscle Strength/physiology , Physical Education and Training/methods , Volleyball/physiology , Adult , Female , Humans , Longitudinal Studies
13.
J Sci Med Sport ; 10(5): 334-40, 2007 Oct.
Article in English | MEDLINE | ID: mdl-16962826

ABSTRACT

The purpose of this investigation was to describe anthropometric and physical performance characteristics of Division I college female lacrosse players. An additional aim of the study was to examine positional differences in this sample of athletes. Eighty-four university lacrosse players (age=19.8+/-1.1 years; height=168.3+/-5.9 cm; body mass=64.7+/-6.9 kg) volunteered to participate and were evaluated at the end of their off-season. Test items included standing height, body mass, linear sprint speed (9.14-36.58 m), agility (pro-agility and Illinois), countermovement jump height and the 20 Meter Shuttle Run Test (MSRT). Standing height was different between positions, pairwise comparisons indicating that attackers were taller than defenders (p=0.029). No other dependent variable differed between positions. Homogeneity between positions for women's lacrosse players indicates that the tests used do not have a high discriminatory value or could reflect the lack of development of positional specificity due to relatively minimal playing experience by participants. Although positional distinctions were not observed in this study, quartiles and ranges provide evidence that performance in female lacrosse players varies markedly.


Subject(s)
Motor Skills , Physical Fitness , Racquet Sports , Adolescent , Adult , Anthropometry , Body Weight , Cohort Studies , Exercise Test , Female , Humans , Reference Values , Running , Students , United States
14.
Sports Med Open ; 3(1): 6, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28101732

ABSTRACT

BACKGROUND: Mechanical loading during exercise has been shown to promote tissue remodeling. Safe and accessible exercise may be beneficial to populations at risk of diminished bone and joint health. We examined the effect of drop height and instruction on knee loading during a drop-landing task and proposed a task that makes use of drop heights that may be appropriate for rehabilitation purposes and functional in daily life to examine transient knee joint loads. METHODS: Twenty males (22.0 ± 2.8 years) performed drop landings from 22 cm (low) and 44 cm (high) heights, each under three instructions: "land naturally" (natural), "softly" (soft), and "stiffly" (stiff). Knee compression force and external flexion moment were estimated using three-dimensional inverse dynamics and normalized to body mass. RESULTS: Peak knee compression force was larger (p < 0.001) for high (17.8 ± 0.63 N/kg) than low (14.8 ± 0.61 N/kg) heights. There was an increase (p < 0.001) in the knee compression force across soft (11.8 ± 0.40 N/kg), natural (17.0 ± 0.62 N/kg), and stiff (20.2 ± 0.67 N/kg) instructions. Peak knee flexion moment in high-natural (2.12 ± 0.08 Nm/kg) was larger (p < 0.001) than in high-soft (1.88 ± 0.08 Nm/kg), but lower than in high-stiff (2.23 ± 0.08 Nm/kg). No differences in peak knee flexion moment were observed across instructions for the low height. CONCLUSIONS: We propose a drop-landing task that creates a scalable increase in knee compression loading. The absence of increased knee flexion moment with drop from the low height, compared to high, suggests that individuals could perform the task without incremental risk of knee injury. This task could be used in future studies to examine the effect of acute bouts of mechanical loading on bone and cartilage metabolism.

15.
Res Q Exerc Sport ; 87(1): 68-77, 2016.
Article in English | MEDLINE | ID: mdl-26889584

ABSTRACT

PURPOSE: The purpose of this study was to quantify the locomotor, heart-rate, and metabolic power characteristics of high-level youth female field hockey matches. METHOD: Players from the U21 and U17 Canadian women's national teams were monitored during a 4-match test series using Global Positioning System technology. Position (forward, midfielder, defender) and age-group (U21, U17) comparisons were made using 2-way analyses of variance. RESULTS: Forwards played 12 min to 22 min fewer than midfielders and defenders and consequently had lower amounts of total, low-intensity, and moderate-intensity distances. Yet, forwards covered similar amounts of high-intensity running and sprinting distances despite the deficit in playing time. Only 10% to 15% of total distance was characterized by high-intensity running and sprinting, yet the majority of time was spent above 90% maximum heart rate. The distances in high, elevated, and maximal metabolic power categories were greater for U21 than U17 players. Yo-Yo Intermittent Recovery Test performance was related to high-intensity running and maximal metabolic power distance. CONCLUSIONS: The current findings highlight positional specificity as well as developmental gaps between age groups for youth female field hockey matches. These match characteristics should be used to assist in establishing appropriate training strategies through the developmental pathway and to assist player achievement to higher standards.


Subject(s)
Athletic Performance/physiology , Heart Rate , Hockey/physiology , Adolescent , Athletes , Canada , Female , Geographic Information Systems , Humans , Physical Endurance/physiology , Time and Motion Studies , Young Adult
16.
Med Sci Sports Exerc ; 53(1): 244, 2021 01.
Article in English | MEDLINE | ID: mdl-33323829
17.
Article in English | MEDLINE | ID: mdl-27574474

ABSTRACT

OBJECTIVES: The purpose of this study was to examine whether field-based and/or laboratory-based assessments are valid tools for predicting key performance characteristics of skating in competitive-level female hockey players. DESIGN: Cross-sectional study. METHODS: Twenty-three female ice hockey players aged 15-25 years (body mass: 66.1±6.3 kg; height: 169.5±5.5 cm), with 10.6±3.2 years playing experience volunteered to participate in the study. The field-based assessments included 20 m sprint, squat jump, countermovement jump, 30-second repeated jump test, standing long jump, single-leg standing long jump, 20 m shuttle run test, isometric leg pull, one-repetition maximum bench press, and one-repetition maximum squats. The laboratory-based assessments included body composition (dual energy X-ray absorptiometry), maximal aerobic power, and isokinetic strength (Biodex). The on-ice tests included agility cornering s-turn, cone agility skate, transition agility skate, and modified repeat skate sprint. Data were analyzed using stepwise multivariate linear regression analysis. Linear regression analysis was used to establish the relationship between key performance characteristics of skating and the predictor variables. RESULTS: Regression models (adj R (2)) for the on-ice variables ranged from 0.244 to 0.663 for the field-based assessments and from 0.136 to 0.420 for the laboratory-based assessments. Single-leg tests were the strongest predictors for key performance characteristics of skating. Single leg standing long jump alone explained 57.1%, 38.1%, and 29.1% of the variance in skating time during transition agility skate, agility cornering s-turn, and modified repeat skate sprint, respectively. Isokinetic peak torque in the quadriceps at 90° explained 42.0% and 32.2% of the variance in skating time during agility cornering s-turn and modified repeat skate sprint, respectively. CONCLUSION: Field-based assessments, particularly single-leg tests, are an adequate substitute to more expensive and time-consuming laboratory assessments if the purpose is to gain knowledge about key performance characteristics of skating.

18.
J Steroid Biochem Mol Biol ; 93(1): 35-42, 2005 Jan.
Article in English | MEDLINE | ID: mdl-15748830

ABSTRACT

The purpose of the present investigation was to examine androgen receptor (AR) content in the vastus lateralis following two resistance exercise protocols of different volume. Nine resistance-trained men (age=24.3+/-4.4 years) performed the squat exercise for 1 (SS) and 6 sets (MS) of 10 repetitions in a random, counter-balanced order. Muscle biopsies were performed at baseline, and 1h following each protocol. Blood was collected prior to, immediately following (IP), and every 15 min after each protocol for 1h. No acute elevations in serum total testosterone were observed following SS, whereas significant 16-23% elevations were observed at IP, 15, and 30 min post-exercise following MS. No acute elevations in plasma cortisol were observed following SS, whereas significant 31-49% elevations were observed for MS at IP, 15, and 30 min post-exercise. Androgen receptor content did not change 1h following SS but significantly decreased by 46% following MS. These results demonstrated that a higher volume of resistance exercise resulted in down-regulation of AR content 1h post-exercise. This may have been due to greater protein catabolism associated with the higher level of stress following higher-volume resistance exercise.


Subject(s)
Exercise , Receptors, Androgen/metabolism , Weight Lifting , Adult , Androgens/blood , Biopsy , Blotting, Western , Body Composition , Diet Records , Enzyme-Linked Immunosorbent Assay , Humans , Hydrocortisone/blood , Lactic Acid/blood , Male , Muscle Contraction , Muscle, Skeletal/metabolism , Receptors, Androgen/genetics , Sex Hormone-Binding Globulin/analysis , Testosterone/blood , Time Factors
19.
Med Sci Sports Exerc ; 37(3): 395-403, 2005 Mar.
Article in English | MEDLINE | ID: mdl-15741837

ABSTRACT

PURPOSE: The purpose of this investigation was to examine the influence of resistance training on circulating concentrations of growth hormone binding protein (GHBP) in response to acute heavy resistance exercise. METHODS: Using a cross-sectional experimental design, a group of resistance-trained men (RT, N=9, 7.9+/-1.3 yr resistance training experience) and a group of untrained men (UT, N=10) performed an acute heavy resistance exercise protocol (AHREP) consisting of 6 sets of 10 repetition maximum parallel squats. Blood samples were obtained 72 h before exercise, immediately before exercise, and 0, 15, 30, 45, and 60 min after exercise. RESULTS: Significant increases (P<0.05) in GHBP, immunoreactive growth hormone (iGH), and IGF-1 were observed in both subject groups after AHREP. There were no differences (P>0.05) between groups in GHBP at rest or after AHREP. However, RT exhibited a significantly greater iGH response to AHREP than UT subjects, and significantly higher IGF-1 values at rest and after exercise. Significant positive correlations were found between GHBP and BMI, body fat, and leptin in both groups. A significant positive correlation also was observed between resting leptin and GHBP values in UT but not RT subjects. CONCLUSIONS: In summary, these data indicate that resistance training does not increase blood GHBP. Nevertheless, the increases observed with IGF-1 concentrations in the resistance-trained subjects do suggest an apparent adaptation with the regulation of this hormone. If there was in fact an increase in GH sensitivity and GH receptor expression at the liver that was not detected by blood GHBP in this study, it may be possible that factors contributing to the circulating concentration of GHBP other than hepatocytes (e.g., leptin and adipocytes) may serve to mask training-induced increases in circulating GHBP of a hepatic origin, thus masking any detectable increase in GH receptor expression.


Subject(s)
Carrier Proteins/blood , Exercise/physiology , Human Growth Hormone/blood , Weight Lifting/physiology , Adaptation, Physiological/physiology , Adult , Blood Glucose/analysis , Cross-Sectional Studies , Energy Intake/physiology , Humans , Insulin-Like Growth Factor I/analysis , Lactic Acid/blood , Leptin/blood , Male , Rest/physiology
20.
Int J Sports Physiol Perform ; 10(4): 476-81, 2015 May.
Article in English | MEDLINE | ID: mdl-25365248

ABSTRACT

PURPOSE: To examine locomotor demands and metabolic-power characteristics of National Collegiate Athletic Association (NCAA) field hockey matches. METHODS: Using a cross-sectional design, global positioning system (GPS) technology tracked Division I field hockey players from 6 teams during 1 regular-season match (68 player observations). An ANOVA compared locomotor demands and metabolic-power characteristics among positions. Paired t tests compared dependent variables between halves. RESULTS: Defenders played 5-6 min more than midfielders, whereas midfielders played 6-7 min more than forwards. Defenders covered less relative distance (98 m/min) than forwards and midfielders (110-111 m/min), as well as more low-intensity running than forwards and less high-intensity running than midfielders. Lower mean metabolic power (9.3 W/kg) was observed for defenders than forwards and midfielders (10.4 W/kg). There was no difference in playing time between halves; however, all 3 positions had a reduction in relative distance (7-9%) and mean metabolic power (8-9%) during the second half. CONCLUSIONS: Despite more playing time, defenders covered less relative distance and had lower mean metabolic power than other positions. Moderate-intensity, high-intensity, and sprint distance were similar between positions, highlighting the greater relative demands on forwards because they tended to have the least amount of playing time. The reduction of key metrics during the second half was similar among positions and warrants further investigation. These initial results can be used to design position-specific drills or create small-sided games that replicate match demands for NCAA athletes, thus helping establish strategies for developing physiological ability of players at this level.


Subject(s)
Athletes , Athletic Performance , Hockey/physiology , Motor Skills/physiology , Physical Endurance/physiology , Time and Motion Studies , Cross-Sectional Studies , Female , Geographic Information Systems , Humans , Running/physiology , Task Performance and Analysis
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