Physiological responses and performance factors for double-poling and diagonal-stride treadmill roller-skiing time-trial exercise.

PURPOSE: To compare physiological responses between a self-paced 4-min double-poling (DP) time-trial (TTDP) versus a 4-min diagonal-stride (DS) time-trial (TTDS). The relative importance of peak oxygen uptake ([Formula: see text]O2peak), anaerobic capacity, and gross efficiency (GE) for projection of 4-min TTDP and TTDS roller-skiing performances were also examined. METHODS: Sixteen highly trained male cross-country skiers performed, in each sub-technique on separate occasions, an 8 × 4-min incremental submaximal protocol, to assess individual metabolic rate (MR) versus power output (PO) relationships, followed by a 10-min passive break and then the TTDP or TTDS, with a randomized order between sub-techniques. RESULTS: In comparison to TTDS, the TTDP resulted in 10 ± 7% lower total MR, 5 ± 4% lower aerobic MR, 30 ± 37% lower anaerobic MR, and 4.7 ± 1.2 percentage points lower GE, which resulted in a 32 ± 4% lower PO (all P < 0.01). The [Formula: see text]O2peak and anaerobic capacity were 4 ± 4% and 30 ± 37% lower, respectively, in DP than DS (both P < 0.01). The PO for the two time-trial (TT) performances were not significantly correlated (R2 = 0.044). Similar parabolic pacing strategies were used during both TTs. Multivariate data analysis projected TT performance using [Formula: see text]O2peak, anaerobic capacity, and GE (TTDP, R2 = 0.974; TTDS, R2 = 0.848). The variable influence on projection values for [Formula: see text]O2peak, anaerobic capacity, and GE were for TTDP, 1.12 ± 0.60, 1.01 ± 0.72, and 0.83 ± 0.38, respectively, and TTDS, 1.22 ± 0.35, 0.93 ± 0.44, and 0.75 ± 0.19, respectively. CONCLUSIONS: The results show that a cross-country skier's "metabolic profile" and performance capability are highly sub-technique specific and that 4-min TT performance is differentiated by physiological factors, such as [Formula: see text]O2peak, anaerobic capacity, and GE.

Comparison of the effects of velocity-based vs. traditional resistance training methods on adaptations in strength, power, and sprint speed: A systematic review, meta-analysis, and quality of evidence appraisal.

We estimated the effectiveness of using velocity feedback to regulate resistance training load on changes in muscle strength, power, and linear sprint speed in apparently healthy participants. Academic and grey literature databases were systematically searched to identify randomised trials that compared a velocity-based training intervention to a 'traditional' resistance training intervention that did not use velocity feedback. Standardised mean differences (SMDs) were pooled using a random effects model. Risk of bias was assessed with the Risk of Bias 2 tool and the quality of evidence was evaluated using the GRADE approach. Four trials met the eligibility criteria, comprising 27 effect estimates and 88 participants. The main analyses showed trivial differences and imprecise interval estimates for effects on muscle strength (SMD 0.06, 95% CI -0.51-0.63; I2 = 42.9%; 10 effects from 4 studies; low-quality evidence), power (SMD 0.11, 95% CI -0.28-0.49; I2 = 13.5%; 10 effects from 3 studies; low-quality evidence), and sprint speed (SMD -0.10, 95% CI -0.72-0.53; I2 = 30.0%; 7 effects from 2 studies; very low-quality evidence). The results were robust to various sensitivity analyses. In conclusion, there is currently no evidence that VBT and traditional resistance training methods lead to different alterations in muscle strength, power, or linear sprint speed.

The dose-response relationship between interval-training and VO2max in well-trained endurance runners: A systematic review.

Success in endurance running is primarily determined by maximal aerobic power (VO2max), fractional utilization, and running economy (RE). Within the literature, two training modalities have been identified to improve VO2max; continuous training (CT) and interval-training (IT). The efficacy of IT to improve VO2max in well-trained runners remains equivocal, as does whether a dose-response relationship exists between the IT training load performed and changes in VO2max. A keyword search was performed in five electronic databases. Seven studies met the inclusion criteria for this systematic review. The training impulse (TRIMP) was calculated to analyse relationships between training load and changes in VO2max, by calculating the time accumulated in certain intensity domains throughout a training intervention. Non-significant (P>0.05) improvements in VO2max were reported in six studies, with only one study reporting a significant (P<0.05) improvement following the IT interventions. A relationship between the training session impulse of the interval-training performed (IT STRIMP) and VO2max improvements were observed. The efficacy of IT to improve VO2max in well-trained runners remains equivocal, nevertheless, the novel method of training-load analysis demonstrates a relationship between the IT STRIMP and VO2max improvements. This provides practical application for the periodization of IT within the training regime of well-trained distance runners.

Development in Adolescent Middle-Distance Athletes: A Study of Training Loadings, Physical Qualities, and Competition Performance.

ABSTRACT: Jones, TW, Shillabeer, BC, Ryu, JH, and Cardinale, M. Development in adolescent middle-distance athletes: a study of training loadings, physical qualities, and competition performance. J Strength Cond Res 35(12S): S103-S110, 2021-The purpose of this study was to examine changes in running performance and physical qualities related to middle-distance performance over a training season. The study also examined relationships between training loading and changes in physical qualities as assessed by laboratory and field measures. Relationships between laboratory and field measures were also analyzed. This was a 9-month observational study of 10 highly trained adolescent middle-distance athletes. Training intensity distribution was similar over the observational period, whereas accumulated and mean distance and training time and accumulated load varied monthly. Statistically significant (p < 0.05) and large effect sizes (Cohen's d) (>0.80) were observed for improvements in: body mass (5.6%), 600-m (4.6%), 1,200-m (8.7%), and 1,800-m (6.1%) time trial performance, critical speed (7.1%), V̇o2max (5.5%), running economy (10.1%), vertical stiffness (2.6%), reactive index (3.8%), and countermovement jump power output relative to body mass (7.9%). Improvements in 1,800 m TT performance were correlated with increases in V̇o2max (r = 0.810, p = 0.015) and critical speed (r = 0.918, p = 0.001). Increases in V̇o2max and critical speed were also correlated (r = 0.895, p = 0.003). Data presented here indicate that improvements in critical speed may be reflective of changes in aerobic capacity in adolescent middle-distance athletes.

The impact of all-rounders and team injury status on match and series success in international cricket.

The association between injury status of the team and all-rounders on match outcome were investigated in international cricketers. Time and non-time loss injuries were recorded over a 32-month period in 47 senior international cricketers. Team injury status was expressed on a 1-4 scale from "fully available" to "unavailable". Generalised linear model (GLM) was employed to examine whether team injury status and the injury status of all-rounders (AR) and single skill (SS) players was associated with the outcome of the match or series. A significant association between team injury status and match and series outcome was found. Team mean injury status was 12.0% lower (P < 0.001; ES = 1.06) during successful series wins and 7.8% lower (P < 0.001; ES = 0.66) during successful match outcomes. Skill group injury status was also significantly associated with match (P = 0.001) and series (P = 0.001) outcomes with AR exhibiting greater injury status than SS cricketers (P < 0.001, ES = 0.44). All injuries, irrespective of time lost, influence the outcome of international cricket series' and matches with injuries to AR having a higher impact on the results. The findings will impact on the injury prevention strategies in elite cricket.

Influence of Environmental Conditions on Performance and Heart Rate Responses to the 30-15 Incremental Fitness Test in Rugby Union Athletes.

Natera, AOW, Jennings, J, Oakley, AJ, and Jones, TW. Influence of environmental conditions on performance and heart rate responses to the 30-15 incremental fitness test in rugby union athletes. J Strength Cond Res 33(2): 486-491, 2019-The purpose of this study was to examine the differences in performance and heart rate (HR) responses between a high heat outdoor condition (34.0° C, 64.1% humidity) and a temperate indoor condition (22.0° C, 50.0% humidity) during the 30-15 intermittent fitness test (30-15IFT). Eight highly trained Rugby Union players (28.1 ± 1.5 years, 181.4 ± 8.8 cm, 88.4 ± 13.3 kg) completed the 30-15IFT in 2 different temperature conditions. Dependent variables recorded and analyzed included: final running speed of the 30-15IFT, HR at rest (HR rest), maximum HR (Max HR), HR recovery, average HR (HR ave), and submaximal HR corresponding to 25, 50, and 75% of final test speed (HR 25%, HR 50%, and HR 75%) and HR at 13 km·h (HR 13 km·h). Greater running speeds were achieved when the test was conducted indoors (19.4 ± 0.7 km·h vs. 18.6 ± 0.6 km·h, p = 0.002, d = 1.67). Average HR and HR 13 km·h were greater when the test was conducted outdoors (p ≤ 0.05, d > 0.85). Large effect sizes were observed for the greater HR at submaximal intensities (d > 0.90). The results of this study highlight the influence of temperature on 30-15IFT performance and cardiac responses. It is recommended that prescription of training based on 30-15IFT results reflects the temperature that the training will be performed in and that practitioners acknowledge that a meaningful change in assessment results can be the result of seasonal temperature change rather than training-induced change.

Current nonclinical testing paradigm enables safe entry to First-In-Human clinical trials: The IQ consortium nonclinical to clinical translational database.

The contribution of animal testing in drug development has been widely debated and challenged. An industry-wide nonclinical to clinical translational database was created to determine how safety assessments in animal models translate to First-In-Human clinical risk. The blinded database was composed of 182 molecules and contained animal toxicology data coupled with clinical observations from phase I human studies. Animal and clinical data were categorized by organ system and correlations determined. The 2×2 contingency table (true positive, false positive, true negative, false negative) was used for statistical analysis. Sensitivity was 48% with a 43% positive predictive value (PPV). The nonhuman primate had the strongest performance in predicting adverse effects, especially for gastrointestinal and nervous system categories. When the same target organ was identified in both the rodent and nonrodent, the PPV increased. Specificity was 84% with an 86% negative predictive value (NPV). The beagle dog had the strongest performance in predicting an absence of clinical adverse effects. If no target organ toxicity was observed in either test species, the NPV increased. While nonclinical studies can demonstrate great value in the PPV for certain species and organ categories, the NPV was the stronger predictive performance measure across test species and target organs indicating that an absence of toxicity in animal studies strongly predicts a similar outcome in the clinic. These results support the current regulatory paradigm of animal testing in supporting safe entry to clinical trials and provide context for emerging alternate models.

Regulatory Forum Opinion Piece*: Use and Utility of Animal Models of Disease for Nonclinical Safety Assessment: A Pharmaceutical Industry Survey.

An Innovation and Quality (IQ) Consortium focus group conducted a cross-company survey to evaluate current practices and perceptions around the use of animal models of disease (AMDs) in nonclinical safety assessment of molecules in clinical development. The IQ Consortium group is an organization of pharmaceutical and biotechnology companies with the mission of advancing science and technology. The survey queried the utilization of AMDs during drug discovery in which drug candidates are evaluated in efficacy models and limited short-duration non-Good Laboratory Practices (GLP) toxicology testing and during drug development in which drug candidates are evaluated in GLP toxicology studies. The survey determined that the majority of companies used AMDs during drug discovery primarily as a means for proactively assessing potential nonclinical safety issues prior to the conduct of toxicology studies, followed closely by the use of AMDs to better understand toxicities associated with exaggerated pharmacology in traditional toxicology models or to derisk issues when the target is only expressed in the disease state. In contrast, the survey results indicated that the use of AMDs in development is infrequent, being used primarily to investigate nonclinical safety issues associated with targets expressed only in disease states and/or in response to requests from global regulatory authorities.

Variances in Strength and Conditioning Practice in Elite Rugby Union Between the Northern and Southern Hemispheres.

Jones, TW, Smith, A, Macnaughton, LS, and French, DN. Variances in strength and conditioning practice in elite Rugby Union between the Northern and Southern hemispheres. J Strength Cond Res 31(12): 3358-3371, 2017-The strength and conditioning (S and C) practices in elite Rugby Union (RU) have previously been detailed. There is also research that indicates playing styles can differ between Northern hemisphere (NH) and Southern hemisphere (SH) teams. It is not presently known if these variances in playing styles are reflected in the S and C practices of those supporting NH and SH teams. As such, the present study examines any variances in S and C practices between those supporting NH and SH elite-level teams. A validated questionnaire was employed that comprised 7 sections: personal details, physical testing, strength and power development, concurrent training, unique aspects of the program, and any further relevant information regarding prescribed training programs. Forty (20 NH, 20 SH, 38 males, 2 females; 33.0 ± 5.5 years) of 52 (77%) coaches responded to the questionnaire. All practitioners worked with international level or professional RU athletes. The primary variances in S and C practice between NH and SH coaches included utilization of differing tests of anaerobic capacity and cardiovascular endurance and differing prescription of compound and Olympic lifts. Also, NH coaches placed a greater emphasis on strength and power training, whereas SH coaches had a more objective approach to determining strength training loads. Furthermore, SH practitioners placed more emphasis on integration compared with NH practitioners. Other aspects of S and C practice detailed in this article appear to be similar between NH and SH practitioners. This research represents the only published survey to date of differing S and C practices in NH and SH RU.

Performance and Endocrine Responses to Differing Ratios of Concurrent Strength and Endurance Training.

The present study examined functional strength and endocrine responses to varying ratios of strength and endurance training in a concurrent training regimen. Thirty resistance trained men completed 6 weeks of 3 d·wk of (a) strength training (ST), (b) concurrent strength and endurance training ratio 3:1 (CT3), (c) concurrent strength and endurance training ratio 1:1 (CT1), or (d) no training (CON). Strength training was conducted using whole-body multijoint exercises, whereas endurance training consisted of treadmill running. Assessments of maximal strength, lower-body power, and endocrine factors were conducted pretraining and after 3 and 6 weeks. After the intervention, ST and CT3 elicited similar increases in lower-body strength; furthermore, ST resulted in greater increases than CT1 and CON (all p ≤ 0.05). All training conditions resulted in similar increases in upper-body strength after training. The ST group observed greater increases in lower-body power than all other conditions (all p ≤ 0.05). After the final training session, CT1 elicited greater increases in cortisol than ST (p = 0.008). When implemented as part of a concurrent training regimen, higher volumes of endurance training result in the inhibition of lower-body strength, whereas low volumes do not. Lower-body power was attenuated by high and low frequencies of endurance training. Higher frequencies of endurance training resulted in increased cortisol responses to training. These data suggest that if strength development is the primary focus of a training intervention, frequency of endurance training should remain low.

Strength and Conditioning and Concurrent Training Practices in Elite Rugby Union.

Jones, TW, Smith, A, Macnaughton, LS, and French, DN. Strength and Conditioning and Concurrent Training Practices in Elite Rugby Union. J Strength Cond Res 30(12): 3354-3366, 2016-There is limited published research on strength and conditioning (S&C) practices in elite rugby union (RU). Information regarding testing batteries and programme design would provide valuable information to both applied practitioners and researchers investigating the influence of training interventions or preperformance strategies. The aim of this study was to detail the current practices of S&C coaches and sport scientists working in RU. A questionnaire was developed that comprised 7 sections: personal details, physical testing, strength and power development, concurrent training, flexibility development, unique aspects of the programme, and any further relevant information regarding prescribed training programmes. Forty-three (41 men, 2 women; age: 33.1 ± 5.3 years) of 52 (83%) coaches responded to the questionnaire. The majority of practitioners worked with international level and/or professional RU athletes. All respondents believed strength training benefits RU performance and reported that their athletes regularly performed strength training. The clean and back squat were rated the most important prescribed exercises. Forty-one (95%) respondents reported prescribing plyometric exercises and 38 (88%) indicated that periodization strategies were used. Forty-two (98%) practitioners reported conducting physical testing, with body composition being the most commonly tested phenotype. Thirty-three (77%) practitioners indicated that the potential muted strength development associated with concurrent training was considered when programming and 27 (63%) believed that strength before aerobic training was more favorable for strength development than vice versa. This research represents the only published survey to date of S&C practices in northern and southern hemisphere RU.

Performance and neuromuscular adaptations following differing ratios of concurrent strength and endurance training.

The interference effect attenuates strength and hypertrophic responses when strength and endurance training are conducted concurrently; however, the influence of training frequency on these responses remain unclear when varying ratios of concurrent strength and endurance training are performed. Therefore, the purpose of the study was to examine the strength, limb girth, and neuromuscular adaptations to varying ratios of concurrent strength and endurance training. Twenty-four men with >2 years resistance training experience completed 6 weeks of 3 days per week of (a) strength training (ST), (b) concurrent strength and endurance training ratio 3:1 (CT3), (c) concurrent strength and endurance training ratio 1:1 (CT1), or (d) no training (CON) in an isolated limb model. Assessments of maximal voluntary contraction by means of isokinetic dynamometry leg extensions (maximum voluntary suppression [MVC]), limb girth, and neuromuscular responses through electromyography (EMG) were conducted at baseline, mid-intervention, and postintervention. After training, ST and CT3 conditions elicited greater MVC increases than CT1 and CON conditions (p ≤ 0.05). Strength training resulted in significantly greater increases in limb girth than both CT1 and CON conditions (p = 0.05 and 0.004, respectively). The CT3 induced significantly greater limb girth adaptations than CON condition (p = 0.04). No effect of time or intervention was observed for EMG (p > 0.05). In conclusion, greater frequencies of endurance training performed increased the magnitude of the interference response on strength and limb girth responses after 6 weeks of 3 days a week of training. Therefore, the frequency of endurance training should remain low if the primary focus of the training intervention is strength and hypertrophy.

Using Multivariate Data Analysis to Project Performance in Biathletes and Cross-Country Skiers.

PURPOSE: To determine whether competitive performance, as defined by International Biathlon Union (IBU) and International Ski Federation (FIS) points in biathlon and cross-country (XC) skiing, respectively, can be projected using a combination of anthropometric and physiological metrics. Shooting accuracy was also included in the biathlon models. METHODS: Data were analyzed using multivariate methods from 45 (23 female and 22 male) biathletes and 202 (86 female and 116 male) XC skiers who were all members of senior national teams, national development teams, or ski-university or high school invite-only programs (age range: 16-36 y). Anthropometric and physiological characteristics were assessed via dual-energy X-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Shooting accuracy was assessed via an outdoor standardized testing protocol. RESULTS: Valid projective models were identified for female biathletes' IBU points (R2 = .80/Q2 = .65) and female XC skiers' FIS distance (R2 = .81/Q2 = .74) and sprint (R2 = .81/Q2 = .70) points. No valid models were identified for the men. The most important variables for the projection of IBU points were shooting accuracy, speeds at blood lactate concentrations of 4 and 2 mmol·L-1, peak aerobic power, and lean mass. The most important variables for the projection of FIS distance and sprint points were speeds at blood lactate concentrations of 4 and 2 mmol·L-1 and peak aerobic power. CONCLUSIONS: This study highlights the relative importance of specific anthropometric, physiological, and shooting-accuracy metrics in female biathletes and XC skiers. The data can help to identify the specific metrics that should be targeted when monitoring athletes' progression and designing training plans.

An Analysis of Warm-Up Strategies at a Cross-Country Skiing National Championship.

PURPOSE: To provide a descriptive analysis of the warm-up (WU) strategies employed by cross-country skiers prior to distance and sprint competitions at a national championship and to compare the skiers' planned and executed WUs prior to the respective competitions. METHODS: Twenty-one national- and international-level skiers (11 women and 10 men) submitted WU plans prior to the distance and sprint competitions, and after the competitions, reported any deviations from the plans. Skiers used personal monitors to record heart rate (HR) during WU, races, and cooldown. Quantitative statistical analyses were conducted on WU durations, durations in HR-derived intensity zones, and WU loads. Qualitative analyses were conducted on skiers' WU plans and their reasons for deviating from the plans. RESULTS: Skiers' planned WUs were similar in content and planned time in HR-derived intensity zones for both the distance and sprint competitions. However, 45% of the women and 20% of the men reported that their WU was not carried out as planned, with reasons detailed as being due to incorrect intensities and running out of time. WU activities including skiing across variable terrain, muscle-potentiating exercises, and heat-maintenance strategies were missing from the skiers' planned routines. CONCLUSIONS: Skiers favored a long, traditional WU approach for both the sprint and distance events, performing less high-intensity and more moderate-intensity exercise during their WUs than planned. In addition, elements likely relevant to successful performance in cross-country skiing were missing from WU plans.

Absence of evidence of translocation of GLUT2 to the apical membrane of enterocytes in everted intestinal sleeves.

INTRODUCTION: Traditional models of intestinal glucose absorption confine GLUT2 to the basolateral membrane. Evidence suggests that GLUT2 is translocated to the apical membrane when the enterocyte is exposed to high luminal glucose concentrations. HYPOTHESIS: GLUT2 translocates to the apical membrane by a PKC signaling mechanism dependent on activity of SGLT1 and the cellular cytostructure. METHODS: Transporter-mediated glucose uptake was studied in rat jejunum using everted sleeves under seven conditions: Control, SGLT1 inhibition (phlorizin), GLUT2 inhibition (phloretin), both SGLT1 and GLUT2 inhibition, PKC inhibition (calphostin C or chelerythrine), and disruption of cellular cytostructure (nocodazole). Each condition was tested in iso-osmotic solutions of 1, 20, or 50 mM glucose for 1 or 5 min incubations (n = 6 rats each). RESULTS: Control rats exhibited a saturable pattern of uptake at both durations of incubation. Phlorizin (P ≤ 0.006 each) inhibited markedly and phloretin (P ≤ 0.01 each) inhibited partially glucose uptake in all concentrations and time. Phloretin and phlorizin together completely inhibited uptake (P = 0.004 each). Calphostin C, chelerythrine, and nocodazole had little effect on glucose uptake at either 1 or 5 min. Inhibition of SGLT1 led to near complete cessation of transporter-mediated glucose uptake, while GLUT2 inhibition led to partial inhibition, suggesting some constitutive expression of GLUT2 in the apical membrane. Disruption of PKC signaling or cytoskeletal integrity partially inhibited transporter-mediated glucose uptake only in 1 mM glucose, suggesting a non-specific effect. CONCLUSIONS: Under these conditions, it does not appear that GLUT2 is translocated to the apical membrane on the cellular cytostructure in response to PKC signaling.

Anthropometric, Physiological, and Performance Developments in Cross-country Skiers.

PURPOSE: This study aimed to describe changes in laboratory-assessed anthropometric and physiological characteristics, training volumes, and competitive performance in national development-team cross-country skiers over a 25-month period, and to analyze whether changes in competitive performance could be predicted by changes in laboratory-assessed qualities and training volumes. METHODS: Data collected over 25 months from 30 national development-team cross-country skiers (14 women, 16 men; age, 18-23 yr) were analyzed retrospectively using multivariate statistics. Anthropometric and physiological characteristics were assessed via dual-energy x-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Total training volumes and distributions of low- and high-intensity training were analyzed from online training diaries, and competitive performance was determined by International Ski Federation (FIS) distance and sprint points. RESULTS: Whole- and upper-body lean mass increased in the full cohort of skiers (n = 30; both P < 0.05), whereas lower-body lean mass, whole-body fat mass, speed and oxygen uptake (V˙O2) at a blood lactate concentration (BLa) of 2 and 4 mmol·L-1, as well as time-trial completion time, power output, and peak V˙O2, improved in the women only (all P < 0.05). Valid predictive models were identified for female skiers' best FIS distance points (R2 = 0.81/Q2 = 0.51) and changes in FIS distance points (R2 = 0.83/Q2 = 0.54), with body mass, fat mass, lean mass, V˙O2peak, and speed at a BLa of 4 mmol·L-1 identified as consistently important variables for projection. CONCLUSIONS: The valid prediction of competitive performance was achieved for women only in distance events. This study suggests that improvements in body composition and aerobic capacity may be more beneficial for elite female development-level skiers than for their male counterparts. These results have implications for athlete selection and performance development.

Variability and physical demands of international seam bowlers in one-day and Twenty20 international matches across five years.

OBJECTIVES: To quantify and compare the match demands and variability of international One-Day (ODI) with Twenty20 (T20) cricket matches and to compare ODI match demands when competing home and away. DESIGN: Single cohort, longitudinal observation. METHODS: Thirteen international male seam bowlers across 204matches (ODI=160; T20=44) were investigated over five-years (2015-2019). Using global positioning sensors and accelerometers, physical demands were quantified using distance covered at different velocities and the number of entries into high and low intensity acceleration and deceleration bands. Variability was quantified using coefficient of variation (CV) and smallest worthwhile change. RESULTS: Significantly greater (p<0.05) match demands were found for all physical variables relative to minutes played for T20 against ODI matches, except for distance covered 20-25kmh-1 which was greater for ODI. Distance covered between 0-7km∙h-1 showed no significance difference (p=0.60). The number of moderate decelerations (2-4m∙s2) were greater (p=0.04) away compared to home in ODI. All other variables showed no significance. Relative to minutes played, decelerations ≤4m∙s2 (within-player ODI CV=75.5%. T20=72.0%) accelerations >4m∙s2 (within-player ODI CV=79.2%. T20 CV=77.2%. Between-player ODI CV=84.7%. T20=38.8%) and distance covered >25kmh-1 (within-player ODI CV=65.5%. T20=64.1%) showed the greatest variability. CONCLUSIONS: Players are exposed to different physical demands in ODI Vs T20 matches, but not for home Vs away ODI matches. Practitioners should be aware of the large variability in high-speed/intensity accelerations and decelerations across matches.

Skin Temperature, Training Load, and Subjective Muscle Soreness in Junior Endurance Athletes: A Case Study.

CONTEXT: The application of infrared thermography to assess the effects of athletic training is increasing. It is not known if changes in skin temperature (Tsk) as assessed by infrared thermography are affected by the training load or the muscle soreness experienced by the athlete. PURPOSE: To describe the variations in Tsk in body areas affected by running training and examine any relationships with subjective ratings of muscle soreness. The secondary aim was to assess the feasibility of using infrared thermography for assessing training load in 2 junior male middle-distance athletes. METHODS: Data were collected over a 42-d observational period with Tsk of the quadriceps, knees, shins, lateral hamstrings, biceps femoris, and Achilles tendons, and the subjective ratings of muscle soreness were taken each morning prior to any training. All training load was quantified through heart rate, running speed, and distance covered. Changes in Tsk outside the typical error were identified. Relationships between Tsk and subjective ratings of muscle soreness were also examined. RESULTS: Over the 42-d observational period, mean Tsk of the regions of interest was reported outside the typical error on day 31 and day 22 for athletes 1 and 2, respectively. These changes in Tsk did not follow trends similar to those of to training loadings. No significant relationships were observed between Tsk of any regions of interest and muscle soreness. CONCLUSIONS: Although Tsk changed outside the typical error throughout the 42-d observational period, these changes were not reflective of training load quantified through cardiovascular strain or subjective ratings of muscle soreness.

AN ASSESSMENT OF THE CONTRACTILE PROPERTIES OF THE SHOULDER MUSCULATURE IN ELITE VOLLEYBALL PLAYERS USING TENSIOMYOGRAPHY.

BACKGROUND: In volleyball, offensive (Hitters) and defensive players (Non-Hitters) perform differing actions that vary both kinematically and in terms of intensity. This may impose contrasting demands on the musculature involved in performing these actions. Previous research has identified differences in the muscle activation and contractile properties of the lower-body musculature between positions. Additionally, asymmetries between dominant and non-dominant limbs of the upper-body musculature has been observed in athletes performing overhead movements. PURPOSE: The aim of this study was to use Tensiomyography (TMG) to examine the contractile properties of the shoulder musculature in elite volleyball players. STUDY DESIGN: Cross-sectional study. METHODS: Thirty-one elite volleyball players participated in this study (Age: 23 ± 2 yrs, Body Mass: 76.5 ± 9.8 kg, Stature: 181 ± 9.3 cm), 26 of which displayed right-limb dominance and five displayed left-limb dominance. Contractile properties of the shoulder musculature including the anterior deltoid (AD), biceps brachii (BB), posterior deltoid (PD), and the upper trapezius (UT) were assessed bilaterally using TMG measures on one occasion prior to any training or exercise. The contractile measures provided by TMG included the maximal displacement (Dm), contraction time (Tc), delay time (Td), sustain time (Ts), and the relaxation time (Tr). RESULTS: No statistically significant differences were observed between positions or limbs, except that Hitters displayed a significantly lower Ts of the left AD compared to Non-hitters (p = 0.01, ES = 1.02), and significant differences between dominant and non-dominant sides in the Td of the UT in Non-hitters were present (p = 0.05, ES = 0.8). CONCLUSION: These data suggest that irrespective of playing position and limb dominance, contractile properties of the shoulder musculature in elite volleyball players, as measured using TMG, display few significant differences. LEVELS OF EVIDENCE: 3b.

Optimization of Exercise Countermeasures for Human Space Flight: Operational Considerations for Concurrent Strength and Aerobic Training.

The physiological challenges presented by space flight and in microgravity (µG) environments are well documented. µG environments can result in declines muscle mass, contractile strength, and functional capabilities. Previous work has focused on exercise countermeasures designed to attenuate the negative effects of µG on skeletal muscle structure, function, and contractile strength and aerobic fitness parameters. Exposure to µG environments influences both strength and aerobic type physical qualities. As such, the current exercise recommendations for those experiencing µG involve a combination of strength and aerobic training or "concurrent training." Concurrent training strategies can result in development and maintenance of both strength and aerobic capabilities. However, terrestrial research has indicated that if concurrent training strategies are implemented inappropriately, strength development can be inhibited. Previous work has also demonstrated that the aforementioned inhibition of strength development is dependent on the frequency of aerobic training, modality of aerobic training, the relief period between strength and aerobic training, and the intra-session sequencing of strength and aerobic training. While time constraints and feasibility are important considerations for exercise strategies in µG, certain considerations could be made when prescribing concurrent strength and aerobic training to those experiencing human space flight. If strength and aerobic exercise must be performed in close proximity, strength should precede aerobic stimulus. Eccentric strength training methods should be considered to increase mechanical load and reduce metabolic cost. For aerobic capacity, maintenance cycle and/or rowing-based high-intensity intermittent training (HIIT) should be considered and cycle ergometry and/or rowing may be preferable to treadmill running.