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In articles on the methodology of studies investigating affective and enjoyment responses to high-intensity interval training, we noted that, occasionally, exercise conditions described as involving "high" intensity exhibited heart rates that were only as high as, or even lower than, heart rates recorded during comparator conditions described as being of "moderate" intensity. Drs. Vollaard, Metcalfe, Kinghorn, Jung, and Little suggest instead that exercise intensity in high-intensity interval-training studies can be defined in terms of percentages of peak workload. Although we maintain that defining exercise intensity in terms of percentages of maximal heart rate is a suboptimal way to quantify the degree of homeostatic perturbations in response to exercise, we are unconvinced that definitions of intensity relying solely on workload are appropriate for studies investigating affective and enjoyment responses to exercise. The reason is that affect is theorized to have evolved to relay information about homeostatic perturbations to consciousness. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether performing resistance exercise in hypoxia acutely reduces performance and increases markers of fatigue, and whether these responses are exaggerated if exercising at high versus low work rates (i.e., exercising to failure or volume matched non-failure). Methods: Following a within-subject design, 20 men completed two trials in hypoxia (13% oxygen) and two in normoxia (21% oxygen). The first session for hypoxic and normoxic conditions comprised six sets of bench press and shoulder press to failure (high work rate), while subsequent sessions involved the same volume distributed over 12 sets (low work rate). Physical performance (concentric velocity) and perceptual responses were measured during exercise and for 72 hr post-exercise. Neuromuscular performance (bench throw velocity) was assessed pre- and post-session. Results: Hypoxia did not affect physical performance, neuromuscular performance, and perceptual recovery when exercising at high or low work rates. Higher work rate exercise caused greater acute decrements in physical performance and post-exercise neuromuscular performance and increased perceived exertion and muscle soreness (p ≤ 0.006), irrespective of hypoxia. Conclusions: Hypoxia does not impact on resistance exercise performance or increase markers of physical and perceptual fatigue. Higher exercise work rates may impair physical performance, and exaggerate fatigue compared to low work rate exercise, irrespective of environmental condition. Practitioners can prescribe hypoxic resistance exercise without compromising physical performance or inducing greater levels of fatigue. For athletes who are required to train with high frequency, decreasing exercise work rate may reduce post-exercise markers of fatigue for the same training volume. [ABSTRACT FROM AUTHOR]

Purpose: To compare peak work rate (WRpeak) and associated physiological and biomechanical performance-determining variables between flat and uphill cross-country (XC) sit-skiing. Methods: Fifteen able-bodied male XC skiers completed 2 test sessions, each comprising four 4-minute submaximal stages, followed by an incremental test to exhaustion and a verification test in a sit-ski on a roller-ski treadmill. The test sessions were counterbalanced by the incline, being either 0.5% (FLAT) or 5% (UPHILL). The authors compared WRpeak and peak oxygen uptake, as well as physiological variables, rating of perceived exertion, gross efficiency, and cycle characteristics at identical submaximal work rate, between FLAT and UPHILL. Results: In UPHILL, WRpeak was 35% higher compared to FLAT (P <.001), despite no difference in peak oxygen uptake (P =.9). The higher WRpeak in UPHILL was achieved through more work per cycle, which was enabled by the twice as long poling time, compared to FLAT (P <.001). Submaximal gross efficiency was 0.5 to 2 percentage points lower in FLAT compared to UPHILL (P <.001), with an increasing difference as work rate increased (P <.001). Neither cycle rate nor work per cycle differed between inclines when compared at identical submaximal work rate (P >.16). Conclusions: The longer poling times utilized in uphill XC sit-skiing enable more work per cycle and better gross efficiency, thereby allowing skiers to achieve a higher WRpeak compared to flat XC sit-skiing. However, the similar values of peak oxygen uptake between inclines indicate that XC sit-skiers can tax their cardiorespiratory capacity similarly in both conditions. [ABSTRACT FROM AUTHOR]

This is the first study to estimate risk of heat-related illness in farmworkers using physiological measurements, rather than questionnaires. In addition, this is the first analysis of these data to use quarter hour increments to evaluate the effect of environmental temperature on work rate over the course of a workday. Objective: Estimate the association between environmental temperature (wet bulb globe temperature [WBGT]) and work rate over the course of a workday. Methods: Repeated-measures regression was used to identify characteristics impacting work rate in a cross-sectional study of Latino farmworkers. Minute-by-minute work rate (measured by accelerometer) and WBGT were averaged over 15-minute intervals. Results: Work rate decreased by 4.34 (95% confidence interval [CI], −7.09 to −1.59) counts per minute per degree Celsius WBGT in the previous 15-minute interval. Cumulative quarter hours worked (2.13; 95% CI, 0.82 to 3.45), age (−3.64; 95% CI, −4.50 to −2.79), and dehydration at the end of workday (51.37; 95% CI, 19.24 to 83.50) were associated with counts per minute as were gender, pay type (piece rate vs hourly) and body mass index ≥25 kg/m2. The effects of pay type and body mass index were modified by gender. Conclusion: Increased temperature was associated with a decrease in work rate. [ABSTRACT FROM AUTHOR]

A generalized model for the maximum work rate extractable from the Sun is developed considering a reversible and an endoreversible system to define a more practical upper-bound efficiency for the conversion of solar radiation into work and power. This model is based on a photo-thermal work extractor in communication with a high-temperature radiation reservoir and a low-temperature heat sink. Following the model, a parametric analysis of the concentration acceptance product (ξ) and thermal conductance is performed to identify the interdependence of variables for the solar exergy. The results are compared with existing models to provide a practical baseline of work and power extractable from concentrated solar power plants (CSP) technologies. Therefore, it is possible to quantify the irreversibilities of an idealized thermodynamic system operating between the Sun and the absorber (via radiative transfer) and the environment (via convective transfer). [ABSTRACT FROM AUTHOR]

Objective: Diminished physical capacity is common and progressive in patients undergoing dialysis, who are also prone to deficiency in carnitine, which plays a pivotal role in maintaining skeletal muscle and cardiac function. The present study aimed to evaluate the association of carnitine profile with exercise parameters in patients with incident dialysis. Design and Methods: This was a single-center cross-sectional study including 87 consecutive patients aged 20-90 years who were initiated on dialysis in Keio University Hospital between December 2019 and December 2022 and fulfilled the eligibility criteria. Exercise parameters were evaluated via cardiopulmonary testing (CPX) using the electronically braked STRENGTH ERGO 8 ergometer, whereas the carnitine profile was assessed by determining serum free carnitine (FC), acylcarnitine (AC) levels and AC/FC ratio. Results: The mean cohort age was 62.1 ± 15.2 years, with male and hemodialysis predominance (70% and 73%, respectively). AC/FC was 0.46 ± 0.15, and CPX revealed peak oxygen consumption (VO2) of 13.9 ± 3.7 (mL/kg/min) with percentpredicted peak VO2 of 53.6% ± 14.7% and minute ventilation (VE)/carbon dioxide output (VCO2) slope of 35.1 ± 8.0. Fully-adjusted multivariate linear regression analysis showed that AC/FC was significantly associated with decreased peak VO2 (β, -5.43 [95% confidence interval (CI), -10.15 to -0.70]) and percent-predicted peak VO2 (β, -19.98 [95% CI, -38.43 to -1.52]) and with increased VE/VCO2 slope (β, 13.76 [95% CI, 3.78-23.75]); FC and AC did not exhibit similar associations with these parameters. Moreover, only AC/FC was associated with a decreased peak work rate (WR), percent-predicted WR, anaerobic threshold, delta VO2/delta WR, and chronotropic index. Conclusion: In patients on incident dialysis, exercise parameters, including those related to both skeletal muscle and cardiac function, were strongly associated with AC/FC, a marker of carnitine deficiency indicating altered fatty acid metabolism. Further studies are warranted to determine whether carnitine supplementation can improve exercise capacity in patients on incident dialysis. [ABSTRACT FROM AUTHOR]

Objective: Treatment side effects lead to a negative impact on the quality of life in breast cancer survivors. Exercise is reported to improve the physical and psychological status of these patients. We aimed to investigate the effect of exercise during radiotherapy on physical and psychological status in breast cancer patients. Material and Method: A randomized controlled study was set in outpatient rehabilitation clinic. Histologically proven stage I-III breast cancer patients referred for adjuvant radiotherapy were randomly assigned to a supervised aerobic and strengthening exercise program or usual medical care without exercise training. The primary outcome parameters were Rosenberg Self Esteem Scale (RSES), Short Form-36 (SF_36) Quality of life, Coping Strategies Questionnaire (COPE Inventory), Fatigue Severity Scale (FSS), Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI). End points were assessed 1 week prior to and 1 week following 6 weeks of exercise training. Results: In the repeated measured analysis, BAI and FSS scores decreased, general health (GH) and energy/fatigue (E) scores of SF-36 increased in the exercise group (p=0.045, Cohen d=0.757 for BAI, p=0.02, Cohen d=0.863, p=0.010, Cohen d =1.02 for GH, p=0.032, Cohen d=0.801 for E), while the use of problem-based coping score decreased in the control group (p=0.049, Cohen d=0.641). No significant differences were found in scores for BDI and RSES (p>0.05). Conclusion: In conclusion, supervised comined exercise training during adjuvant radiotherapy improved anxiety, fatigue, energy, general health perceptions and prevented decreasing in using effective coping strategies. [ABSTRACT FROM AUTHOR]

Repeated maximal exercise separated by 24 hours may be useful in identifying possible objective markers in people with ME/CFS that are not present in healthy controls. We aimed to synthesise studies in which the test-to-retest (24 hours) changes in VO2 and work rate have been compared between people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and controls. Seven databases (CINAHL, PubMed, PsycINFO, Web of Knowledge, Embase, Scopus and MEDLINE) were searched. Included studies were observational studies that assessed adults over the age of 18 years with a clinical diagnosis of ME/CFS compared to healthy controls. The methodological quality of included studies was assessed using the Systematic Appraisal of Quality for Observational Research critical appraisal framework. Data from included studies were synthesised using a random effects meta-analysis. The pooled mean decrease in peak work rate (five studies), measured at retest, was greater in ME/CFS by −8.55 (95% CI −15.38 to –1.72) W. The pooled mean decrease in work rate at anaerobic threshold (four studies) measured at retest was greater in ME/CFS by −21 (95%CI −38 to −4, tau = 9.8) W. The likelihood that a future study in a similar setting would report a difference in work rate at anaerobic threshold which would exceed a minimal clinically important difference (10 W) is 78% (95% CI 40%–91%). Synthesised data indicate that people with ME/CFS demonstrate a clinically significant test–retest reduction in work rate at the anaerobic threshold when compared to apparently healthy controls. [ABSTRACT FROM AUTHOR]

Purpose. This study aimed to investigate the influence of the outfield goalkeeper game situation on the running performance of teammates and opponent players during professional futsal matches. Methods. The movement trajectories of 126 professional players during 6 official matches were analysed with a videobased tracking system (30 Hz). Distance covered and percentage of distance covered in different speed ranges were calculated to identify differences per team and per sub-phase of the game (traditional vs. outfield goalkeeper situation). Results. The teammates of the outfield goalkeeper spent a higher percentage of the distance covered in the standing and walking speed range (36.27 ± 15.38%) compared with the teammates of the traditional goalkeeper (31.44 ± 7.74%). The outfield goalkeeper spent a smaller percentage of the distance covered in the standing and walking range (41.13 ± 10.86% vs. 80.77 ± 4.30%) and a higher percentage in the low- and medium-intensity running range (31.59 ± 5.59% vs. 15.07 ± 2.74% and 14.33 ± 3.90% vs. 2.50 ± 1.19%, respectively), as well as covered a greater distance (77.41 ± 16.00 m/min) than the traditional goalkeeper (33.81 ± 3.66 m/min). Conclusions. These findings provide coaches with a background concerning the requirements during the outfield goalkeeper situation as guidelines for final exercises in training sessions. [ABSTRACT FROM AUTHOR]

The environment has the space- and time-dependent temperature HT ht . Consequently, the third term in the r. h. s. of the formula Case 1 of Table 4 decreases and, in turn, the work content factor of the solar energy flux HT ht decreases. The energy balance for the work accumulator is Graph HT ht (17) Usage of eqs. Lower values of HT ht show that there is place for improving the performance of the energy conversion system. [Extracted from the article]

A study was conducted on labour productivity in dairy cattle farms that breed Black-and-White cows. The study encompassed 90 farms, thus including 6471 cows. The farms were divided into four groups: small – 8 farms with an average of 3.6 cows; medium – 32 farms with an average of 22.9 cows; large – 32 farms with an average of 74.2 cows; and huge – 18 farms with 185.3 cows per farms. The results of the study indicated that large and huge farms are distinguished by high labour productivity. The income from production, profit, milk quantities, and the cost of one annual work unit (AWU) and a man-hour were several times higher compared to small and medium farms. Production was organised at a much better technological level, which was a contributing factor towards high-quality and competitive milk production. A recommendation to the small and medium farms would be to grow larger, improve their selection, and develop technologically.

Many birds and mammals show substantial circadian variation in body temperature, which has been attributed to fluctuations in ambient temperature and energy reserves. However, to fully understand the variation in body temperature over the course of the day, we also need to consider effects of variation in work rate. We made use of a dataset on body temperature during the resting and active periods in female marsh tits (Poecile palustris) that bred in a temperate area and were subjected to experimental changes in reproductive investment through brood size manipulations. Furthermore, the amplitude increased with daytime, but were unaffected by nighttime, ambient temperature. Amplitudes in females with manipulated broods were 44% above predictions based on inter-specific allometric relationships. In extreme cases, amplitudes were > 100% above predicted values. However, no individual female realised the maximum potential amplitude (8.5 °C, i.e. the difference between the highest and lowest body temperature within the population) but seemed to prioritise either a reduction in body temperature at night or an increase in body temperature in the day. This suggests that body temperature amplitude might be constrained by costs that preclude extensive use of both low nighttime and high daytime body temperatures within the same individual. Amplitudes in the range found here (0.5–6.7 °C) have previously mostly been reported from sub-tropical and/or arid habitats. We show that comparable values can also be found amongst birds in relatively cool, temperate regions, partly due to a pronounced increase in body temperature during periods with high work rate. [ABSTRACT FROM AUTHOR]

Purpose: To investigate temporal variation in running intensity across and within halves and evaluate the agreement between match-analysis indices used to identify fluctuations in running intensity in rugby sevens. Methods: Data from a 15-Hz global positioning system (GPS) were collected from 12 elite rugby sevens players during the IRB World Sevens Series (N = 21 full games). Kinematic (eg, relative distance [RD]) and energetic (eg, metabolic power [MP]) match-analysis indices were deter- mined from velocity--time curves and used to investigate between-halves variations. Mean MP and RD were used to identify peak 2-minute periods of play. Adjacent 2-minute periods (prepeak and postpeak) were compared with peak periods to identify changes in intensity. MP and RD were expressed relative to maximal oxygen uptake ( ...O2max) and speed at ...O2max, respectively, and compared in their ability to describe the intensity of peak periods and their temporal occurrence. Results: Small to moderate reductions were present for kinematic (RD; 8.9%) and energetic (MP; 6%) indices between halves. Peak periods (RD = 130 m/min, MP =13 W/kg) were higher (P < .001) than the match average (RD = 94 m/min, MP = 9.5 W/kg) and the prepeak and postpeak periods (P < .001). RD underestimated the intensity of peak periods compared with MP (bias 16%, limits of agreement [LoA] ± 6%). Peak periods identified by RD and MP were temporally dissociated (bias 21 s, LoA ± 212 s). Conclusions: The findings suggest that running intensity varies between and within halves; however, the index used will influence both the magnitude and the temporal identification of peak periods. [ABSTRACT FROM AUTHOR]

Objective: Determine compliance with and effectiveness of California regulations in reducing farmworkers' heat-related illness (HRI) risk and identify main factors contributing to HRI. Methods: In a cross-sectional study of Latino farmworkers, core body temperature (CBT), work rate, and environmental temperature (WBGT) were monitored over a work shift by individual ingestible thermistors, accelerometers, and weather stations, respectively. Multiple logistic modeling was used to identify risk factors for elevated CBT. Results: Although farms complied with Cal/OSHA regulations, worker training of HRI prevention and hydration replacement rates were insufficient. In modeling (AOR [95% CI]) male sex (3.74 [1.22 - 11.54]), WBGT (1.22 [1.08 - 1.38]), work rate (1.004 [1.002 - 1.006]), and increased BMI (1.11 [1.10 - 1.29]) were all independently associated with elevated CBT. Conclusion: Risk of HRI was exacerbated by work rate and environmental temperature despite farms following Cal/OSHA regulations. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of age on physical and technical game performance for different positions in professional basketball players. In this cross-sectional study, a total of 25,523 individual match observations were undertaken on players from the 2018–19 NBA season. The players were classified into four age groups (19–22 years, 23–25 years, 26–29 years, and 30–42 years). Differences in physical and technical match performance were analysed for the following variables: distance covered, average speed, minutes played, points scored and playing efficiency. The results showed that players older than 30 covered shorter distance and had lower average speed than younger players, that guards and forwards older than 26 played more minutes per game than younger ones, and that guards older than 26 scored more points and were more efficient than younger one, while centres age 23–25 scored more points per games than centres older than 30. In conclusion, physical performance declined with age, and while playing time and technical performance generally remained stable or increased, especially for guards. However, there was some evidence of decline for centres. [ABSTRACT FROM AUTHOR]

Work rate has a direct impact on the systolic blood pressure (SBP) during aerobic exercise, which may be challenging in the evaluation of the SBP response in athletes reaching high work rates. We aimed to investigate the exercise SBP response in endurance athletes in relation to oxygen uptake (VO2), work rate and to recent reference equations for exercise SBP in the general population. Endurance athletes with a left-ventricular end-diastolic diameter above the reference one performed a maximal bicycle cardiopulmonary exercise test. The increase in SBP during exercise was divided by the increase in VO2 (SBP/VO2 slope) and in Watts, respectively (SBP/W slope). The maximum SBP (SBPmax) and the SBP/W slope were compared to the predicted values. In total, 27 athletes (59% men) were included; mean age, 40 ± 10 years; mean VO2max, 50 ± 5 mL/kg/min. The mean SBP/VO2 slope was 29.8 ± 10.2 mm Hg/L/min, and the mean SBP/W slope was 0.27 ± 0.08 mm Hg/W. Compared to the predicted normative values, athletes had, on average, a 12.2 ± 17.6 mm Hg higher SBPmax and a 0.12 ± 0.08 mm Hg/W less steep SBP/W slope (p < 0.01 and p < 0.001, respectively). In conclusion, the higher SBPmax values and the less steep SBP/W slope highlight the importance of considering work rate when interpreting the SBP response in endurance athletes and suggest a need for specific normative values in athletes to help clinicians distinguish physiologically high maximal blood pressure from a pathological blood pressure response.

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A study was conducted on labour productivity in dairy cattle farms that breed Black-and-White cows. The study encompassed 90 farms, thus including 6471 cows. The farms were divided into four groups: small - 8 farms with an average of 3.6 cows; medium - 32 farms with an average of 22.9 cows; large - 32 farms with an average of 74.2 cows; and huge - 18 farms with 185.3 cows per farms. The results of the study indicated that large and huge farms are distinguished by high labour productivity. The income from production, profit, milk quantities, and the cost of one annual work unit (AWU) and a man-hour were several times higher compared to small and medium farms. Production was organised at a much better technological level, which was a contributing factor towards high-quality and competitive milk production. A recommendation to the small and medium farms would be to grow larger, improve their selection, and develop technologically. [ABSTRACT FROM AUTHOR]

Based on the strong linear relationship between heart rate (HR) and oxygen consumption, the Åstrand-Ryhming cycle ergometer test (Astrand and Ryhming in J Appl Physiol 7:218-221, 1954) is a widely used submaximal test to predict whole body maximal oxygen consumption ([Formula: see text]). However, a similar test predicting peak oxygen consumption ([Formula: see text]) in the upper extremities is not established, and may be very useful for individuals unable to use their lower extremities or/and if separation of upper extremity aerobic capacity is sought after. Thus, the aim of the current study was to develop a submaximal test predicting [Formula: see text] in arm-cycling. Forty-nine healthy volunteers (25 women: 38 ± 13 years; 24 men: 39 ± 12 years) tested arm-cycle [Formula: see text] on a protocol with 4-min, 21-W increments to exhaustion. The data were contrasted to treadmill [Formula: see text] values. Arm-cycle [Formula: see text] was 66 ± 8% of [Formula: see text] (r = 0.92, p < 0.001; women: 1.9 ± 0.4 L min-1; men: 3.0 ± 0.7 L min-1). Arm-cycle HR and [Formula: see text] exhibited correlations of r = 0.79 and r = 0.78 for women and men, respectively, while corresponding correlations between work rate and [Formula: see text] were r = 0.95 (women) and r = 0.89 (men) (all p < 0.001). Arm-cycle [Formula: see text] prediction revealed a standard error of estimate (SEE) of 11.2% (women) and 10.2% (men), and was primarily due to individual arm-cycle maximal HR (women: 173 ± 13 beats min-1; men: 174 ± 10 beats min-1; correction factor: 5-7%). In conclusion, from a single 4-min stage of submaximal arm cycling, [Formula: see text] can be predicted with a SEE of 10-11%. The arm-cycle test may have important value for individuals who rely on arms in sports and occupations, and for patients with lower extremity disabilities. [ABSTRACT FROM AUTHOR]

Purpose: Soccer referees' physical match performances at the start of the second half (46-60 min) were evaluated in relation to both the corresponding phase of the first half (0-15 min) and players' performances during the same match periods. Methods: Match analysis data were collected (Prozone, UK) from 12 soccer referees on 152 English Premier League matches during the 2008/09 soccer season. Physical match performance categories for referees and players were total distance, high-speed running distance (speed >5.5 m/s), and sprinting distance (>7.0 m/s). The referees' heart rate was recorded from the start of their warm-up to the end of the match. The referees" average distances (in meters) from the ball and fouls were also calculated. Results: No substantial differences were observed in duration (16:42 ± 2:35 vs 16:27 ± 1:00 min) or intensity (107 ± 11 vs 106 ± 14 beats/ min) of the referees' preparation periods immediately before each half. Physical match performance was reduced during the initial phase of the second half when compared with the first half in both referees (effect sizes-standardized mean differences-0.19 to 0.73) and players (effect sizes 0.20 to 1.01 ). The degree of the decreased performance was consistent between referees and players for total distance (4.7 m), high-speed running (1.5 m), and sprinting (1.1 m). The referees were closer to the ball (effect size 0.52) during the opening phase the second half. Conclusion: Given the similarity in the referees' preparation periods, it may be that the reduced physical match performances observed in soccer referees during the opening stages of the second half are a consequence of a slower tempo of play. [ABSTRACT FROM AUTHOR]

Cross-country skiing is an endurance sport that requires extremely high maximal aerobic power. Due to downhill sections where the athletes can recover, skiers must also have the ability to perform repeated efforts where metabolic power substantially exceeds maximal aerobic power. Since the duration of these supra-aerobic efforts is often in the order of seconds, heart rate, and pulmonary VO2 do not adequately reflect instantaneous metabolic power. Propulsive power (Pprop) is an alternative parameter that can be used to estimate metabolic power, but the validity of such calculations during cross-country skiing has rarely been addressed. The aim of this study was therefore twofold: to develop a procedure using small non-intrusive sensors attached to the athlete for estimating Pprop during roller-skiing and to evaluate its limits; and (2) to utilize this procedure to determine the Pprop generated by high-level skiers during a simulated distance race. Eight elite male cross-country skiers simulated a 15 km individual distance race on roller skis using ski skating techniques on a course (13.5 km) similar to World Cup skiing courses. Pprop was calculated using a combination of standalone and differential GNSS measurements and inertial measurement units. The method's measurement error was assessed using a Monte Carlo simulation, sampling from the most relevant sources of error. Pprop decreased approximately linearly with skiing speed and acceleration, and was approximated by the equation Pprop(v,v˙) = −0.54·v −0.71·v˙ + 7.26 W·kg−1. Pprop was typically zero for skiing speeds >9 m·s−1, because the athletes transitioned to the tuck position. Peak Pprop was 8.35 ± 0.63 W·kg−1 and was typically attained during the final lap in the last major ascent, while average Pprop throughout the race was 3.35 ± 0.23 W·kg−1. The measurement error of Pprop increased with skiing speed, from 0.09 W·kg−1 at 2.0 m·s−1 to 0.58 W·kg−1 at 9.0 m·s−1. In summary, this study is the first to provide continuous measurements of Pprop for distance skiing, as well as the first to quantify the measurement error during roller skiing using the power balance principle. Therefore, these results provide novel insight into the pacing strategies employed by high-level skiers.

The age of peak performance is likely to vary between sports and competitions, affected by the specific skills and attributes needed to succeed in the particular competition. However, no studies using modern tracking techniques have examined the effects of age on competitive match play performance. Thus, the purpose of this study was to evaluate the effects of age on match physical and technical performance using a large‐scale analysis of match performance in professional soccer players. A total of 14 546 individual match observations were undertaken in the first German league (Bundesliga) during the 2012‐2013, 2013‐2014, and 2014‐2015 seasons using a computerized tracking system (VISTRACK, by Impire Corp.). Differences in physical and technical match performance of soccer players were analyzed for the following variables: total distance covered, number of fast runs, number of sprints, and percentage of successful passes. Professional soccer players aged >30 years showed a significant lower performance in the total distance covered, the number of fast runs, and the number of sprints compared with younger players (≤30 years). Conversely, the player's ability to make successful passes increased with age. These effects were observed in all positional roles except wide midfielders. These findings may help coaches and managers to better understand the effects of age on match‐related physical and technical performance and may have the potential to assist in decisions such as, when a new contract would be signed, the duration of the contract, the salary, or when to replace or transfer a player depending on their age. [ABSTRACT FROM AUTHOR]

Previously, perceived exertion in submaximal resistance exercise protocols was reported to be affected by the intensity of load followed by work-to-rest ratio. Nevertheless, the effect of set configuration, which entails the metabolic, hormonal, and neuromuscular implication of the session, is currently unknown, despite the fact that perceived exertion discriminates these differences. We aimed to analyze the effect of 3 submaximal set configurations on perceived exertion and their relationship with velocity as a mechanical measure of fatigue. Seventeen healthy subjects (23 ± 2 years) performed with the 10-repetition maximum load on the leg press (211 ±45 kg) a total of 40 repetitions with 720 seconds of rest in 3 randomized experimental sessions with the same work-to-rest ratio. The sessions consisted of an interrepetition rest design performing individual repetitions, a cluster design performing groups of 4 repetitions, and a traditional design performing groups of 8 repetitions. At the end of the session, the nonparametric analysis of variance-type test revealed differences between protocols (p < 0.001), with lower values of perceived exertion in the interrepetition rest design in comparison with the cluster design (p = 0.003) and traditional design (p < 0.001). In addition, Spearman's rank correlations (p < 0.001) were observed for the interrepetition rest design (rho = -0.72) and traditional design (rho = -0.8) between perceived exertion and velocity. Our findings suggest that the submaximal set configuration is a determinant of perceived exertion by itself, and that perceived exertion represents similar mechanisms as velocity, such as fatigue and certain characteristics of the session and the individual. [ABSTRACT FROM AUTHOR]

Farm workers are at risk of heat related illness (HRI), but their work rates that contribute to HRI have not been objectively assessed. The CHIPS study collected accelerometer data and characterized the physical activity of major farm tasks. Demographic information, work characteristics, and accelerometer data were collected from 575 farm workers in California. Each participating worker contributed measurements over one work shift. An Actical accelerometer was attached securely to a belt worn at the hip. Data were collected at one-minute intervals throughout the work shift. A total of 13 major work-task categories were defined. The mean physical activity counts per minute (cpm) and percentage of the shift spent at moderate and/or vigorous levels of activity were described for each task. Multiple linear regression models were constructed to determine the worker and environmental characteristics contributing to the physical activity level. Mean levels of physical activity ranged from 700 cpm (workers who carry produce) to a low of 150 cpm "ground pruners" who tend low-level plants, with an overall mean of 345 cpm or "light" activity (2 to ≤3 metabolic equivalents). The environmental temperature was the major factor associated with physical activity. A 10°C increase in the median temperature reduced the mean cpm by 135 (95% CI = 87, 193). Age and the tasks of sorting, ground pruning, and harvesting low-level crops were also negatively and independently associated with mean cpm. Incentivized (piece rate) pay, multi-task work, and irrigator work were positively associated with cpm. An interaction was found between piece rate and sex. Men's activity significantly increased (p < 0.001) by a mean of 95 cpm, (95% CI = 38.3, 150.7) if they were paid by the piece, but there was a non-significant association with women's activity level. Workers conducting multiple tasks, irrigators, men, and those earning incentivized (piece rate) pay had higher adjusted mean physical activity levels and are likely at increased risk of heat-related illness on hot days. [ABSTRACT FROM AUTHOR]

Cross-country skiing is an endurance sport that requires extremely high maximal aerobic power. Due to downhill sections where the athletes can recover, skiers must also have the ability to perform repeated efforts where metabolic power substantially exceeds maximal aerobic power. Since the duration of these supra-aerobic efforts is often in the order of seconds, heart rate, and pulmonary VO2 do not adequately reflect instantaneous metabolic power. Propulsive power (P prop) is an alternative parameter that can be used to estimate metabolic power, but the validity of such calculations during cross-country skiing has rarely been addressed. The aim of this study was therefore twofold: to develop a procedure using small non-intrusive sensors attached to the athlete for estimating P prop during roller-skiing and to evaluate its limits; and (2) to utilize this procedure to determine the P prop generated by high-level skiers during a simulated distance race. Eight elite male cross-country skiers simulated a 15 km individual distance race on roller skis using ski skating techniques on a course (13.5 km) similar to World Cup skiing courses. P prop was calculated using a combination of standalone and differential GNSS measurements and inertial measurement units. The method's measurement error was assessed using a Monte Carlo simulation, sampling from the most relevant sources of error. P prop decreased approximately linearly with skiing speed and acceleration, and was approximated by the equation P prop (v , v ˙ ) = −0.54· v −0.71 · v ˙ + 7.26 W·kg−1. P prop was typically zero for skiing speeds >9 m·s−1, because the athletes transitioned to the tuck position. Peak P prop was 8.35 ± 0.63 W·kg−1 and was typically attained during the final lap in the last major ascent, while average P prop throughout the race was 3.35 ± 0.23 W·kg−1. The measurement error of P prop increased with skiing speed, from 0.09 W·kg−1 at 2.0 m·s−1 to 0.58 W·kg−1 at 9.0 m·s−1. In summary, this study is the first to provide continuous measurements of P prop for distance skiing, as well as the first to quantify the measurement error during roller skiing using the power balance principle. Therefore, these results provide novel insight into the pacing strategies employed by high-level skiers. [ABSTRACT FROM AUTHOR]

Purpose: To report the intensity distribution of Premier League soccer players' external loads during match play, according to recognized physiological thresholds. The authors also present a case in which individualized speed thresholds changed the interpretation of time-motion data. Method: Eight outfield players performed an incremental treadmill test to exhaustion to determine the running speeds associated with their ventilatory thresholds. The running speeds were then used to individualize time-motion data collected in 5 competitive fixtures and compared with commonly applied arbitrary speed zones. Results: Of the total distance covered, 26%, 57%, and 17% were performed at low, moderate, and high intensity, respectively. Individualized time- motion data identified a 41% difference in the high-intensity distance covered between 2 players of the same positional role, whereas the player-independent approach yielded negligible (5-7%) differences in total and high-speed distances covered. Conclusions: The authors recommend that individualized speed thresholds be applied to time-motion-analysis data in synergy with the traditional arbitrary approach. [ABSTRACT FROM AUTHOR]

Objective: To investigate the influence of physical fitness on peak periods of match-play. Methods: Forty-three female Australian footballers from three teams wore global positioning system units in matches during one competitive season. The Yo-Yo Intermittent Recovery Test (Level 1) was conducted as an estimate of physical fitness. One-, two-, three-, four- and five-minute rolling periods were analysed in order to determine the "peak" and "subsequent" periods during match-play. Results: Midfielders covered greater distances during peak periods than half-line players (Effect size, ES range = 0.33–0.86; likelihood ≥76%). Nomeaningful differences were reported between positional groups for high-speed distances during the peak periods, with the exception of half-liners covering greater distance during the 1-minute period (ES = 0.38; likelihood = 80%).Higher fitness players covered greater peak total and high-speed (ES range = 0.70–1.16; likelihood ≥94%) distances than lower fitness players, irrespective of position. Higher fitness midfielders covered greater high-speed distances during the 1 to 3-minute subsequent periods than lower fitness midfielders (ES range = 0.46–0.71; likelihood ≥81%). Half-liners with greater Yo-Yo performances covered greater relative total and low-speed (ES range = 0.47–0.70; likelihood ≥76%) distances during the subsequent periods than lower fitness players. Conclusion: Developing physical fitness may enable greater peak and subsequent period performances and improve players' abilities to maintain higher average match intensities. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the standardized relative distance covered by the various playing positions (defenders, midfielders, and forwards) against different quality of opponents in domestic women's field hockey. Data were collected from 13 individuals competing for 1 team in the English Premier League across an 18-game season. Data were collected using portable global positioning system technology. Distance data were grouped into 6 speed zones relative to individual players' maximum sprint speeds and then standardized by dividing by the number of on-pitch minutes. Dependent variables included distance covered in the 6 speed zones, as well as the number of sprints and repeated sprint efforts (RSEs) completed in the highest speed zone. Participants covered a significantly greater total distance when competing against opponents from top 3 teams compared with middle 3 teams (111.78 ± 2.65 m•min-1 vs. 107.35 ± 2.62 m•min-1, respectively). This was also true for distance covered in zone 4 (running) (29.47 ± 1.69 m•min-1 vs. 27.62 ± 1.45 m•min-1, respectively) and zone 5 (fast running) (23.42 ± 1.76 m•min-1 vs. 21.52 ± 1.79 m•min-1, respectively). Defenders (99.77 ± 4.36 m•min-1 ) covered significantly less total meters per minute than midfielders (117.20 ± 4.36 m•min-1 ) and completed significantly fewer RSEs per on-pitch minute (0.21 ± 0.03 and 0.33 ± 0.03, respectively). Midfielders covered significantly less distance in zone 2 (walking) than forwards (19.38 ± 1.64 m•min-1 and 30.33 ± 2.12 m•min-1, respectively). Conversely, midfielders were shown to cover significantly more distance in zone 3 (jogging) than forwards (32.84 ± 1.10 m•min-1 and 24.61 ± 1.42 m•min-1, respectively). A standardized and relative assessment may be useful for coaches' and performance analysts' understanding of players' performance in different positions or against different quality opponents. [ABSTRACT FROM AUTHOR]

The purpose of the study was to examine the influence of playing congested fixtures (2 matches a week) on running performance of Brazilian professional football players, pooled (all performance files regardless players' rotation between games) or individualized data treatment (including only files of athletes' who played pair(s) of noncongested-congested matches which occurred on the same week). Forty participants were observed 1-37 times during 59 official matches over 3 years. Global positioning system devices were used to compute total distance covered, maximal sprinting speed mean speed (VAVERAGE), and high-intensity activities (HIA: ≥15 km⋅h-1). Independent variables included match status (win, draw, and lose), location (home and away), opponent quality (weak and strong), competitive standard (national and state), team formation (4-4-2 and 4-3-3), and position (defender, midfielder, and forward). Student's t-test, effect sizes (d), and magnitude-based inferences were performed to detect differences between congested and noncongested fixtures for each independent factor. Overall, pooled and individualized data treatment revealed contrasting results. The first showed chances of positive outcomes playing congested matches (possibly to very likely; d = 0.09-0.55), for all variables, as using 4-4-2 and state tournament. Conversely, individualized data analysis revealed that during national leagues (possibly; d = 0.24) or forward position (likely; d = 0.70), the players presented reduced HIA when played congested than noncongested periods (p ≤ 0.05). Using 4-3-3 (d = 0.26) or when draw (d = 0.41), possibly lower HIA was also identified. Coaching staff should be aware of performance oscillations such as detrimental effects on HIA during congested periods. [ABSTRACT FROM AUTHOR]

Field experiments were done to evaluate the impact of soil tillage reduction on energy efficiency and labour productivity in cultivation of winter wheat, spring barley and soybean. Besides the conventional tillage (CT), in nonconventional tillage methods the following implements were used: RT1 - chisel plough, disc harrow, multi-tiller, seeddrill; RT2 - shallow chisel, seed-drill; NT - no-till seed-drill. As the efficiency indicators of different tillage methods, the following parameters were measured: work rate, energy requirement and yield. It was observed that tillage systems greatly differed regarding energy and labour requirements. Substitution of mouldboard plough with chisel in primary tillage provided a substantial specific energy efficiency improvement. Grain yields varied depending on soil tillage method and growing season. The differences in yield were not significant in winter wheat and soybean cultivation, while the yield of spring barley was significantly higher in RT2 and NT variants then in CT. Cereals such as winter wheat and spring barley responded well to the reduction of tillage, and no-till system might be the best option for these crops cultivation. [ABSTRACT FROM AUTHOR]

This research explores the influence of playing with different recovery times between matches on physical activity and technical performance. The sample was composed by 4496 professional players who participated in German professional league (Deutsche Fußball Liga – DFL) during the season 2011–2012. Data were collected using a semi-automatic optical tracking system (VISTRACK, by Impire Corp., Germany). Differences on work rate profiles of soccer players were analysed for the following variables: total distance covered, number of fast runs, number of sprints and percentage of successful passes. The main finding of this study suggests that the total distance covered, the number of fast runs and the number of sprints decreased in professional soccer players in microcycles with length of <4 days during the mid-season. Central defenders, external defenders and external midfielders covered less total distance in microcycles of <4 days, and this effect was more evident during the mid-season. During three-day microcycles in comparison to four-day cycles, central defenders and external defenders reduced the total distance covered. No differences were observed between teams according to the team quality and match location. Coaches should pay extra attention to adapt recovery strategy according to playing position and period of season. [ABSTRACT FROM PUBLISHER]

Ratings of perceived exertion (RPE: 0-10) during resistance training with varying programming demands were examined. Blood lactate (BLa) and muscle activation (using surface electromyography: EMG) were measured as potential mediators of RPE responses. Participants performed three sets of single arm (preferred side) bicep curls at 70% of 1 repetition maximum over 4 trials: Trial (A) 3 sets × 8 repetitions × 120 s recovery between sets; (B) 3 sets × 8 repetitions × 240 s recovery; (C) 3 sets × maximum number of repetitions (MNR) × 120 s recovery; (D) 3 sets ×MNR× 240 s recovery. Overall body (RPE-O) and active muscle (RPE-AM) perceptual responses were assessed following each set in each trial. Biceps brachii and brachioradialis muscle EMG was measured during each set for each trial. RPE-O and RPE-AM were not different between Trial A (3.5 ± 1 and 6 ± 1, respectively) and Trial B (3.5 ± 1 and 5.5 ± 1, respectively) (p < .05). However, RPE-AM was significantly greater in Trial C (7.5 ± 1.5) and Trial D (7.5 ± 1.5) than in Trial B (p < .05). There were no significant differences in muscle activation or BLa between trials; however, work rate (tonnage/min) was greater in Trials C and D compared to Trial B. In conclusion, BLa and muscle activation were not related to RPE, but resistance training variables, such as work rate, may impact on RPE when intensity (%1RM) and the number of sets completed remain constant. [ABSTRACT FROM AUTHOR]

In a new approach based on adaptive neuro-fuzzy inference systems (ANFIS), field heart rate (HR) measurements were used to classify work rate into four categories: very light, light, moderate, and heavy. Inter-participant variability (physiological and physical differences) was considered. Twenty-eight participants performed Meyer and Flenghi's step-test and a maximal treadmill test, during which heart rate and oxygen consumption (VO2) were measured. Results indicated that heart rate monitoring (HR, HRmax, and HRrest) and body weight are significant variables for classifying work rate. The ANFIS classifier showed superior sensitivity, specificity, and accuracy compared to current practice using established work rate categories based on percent heart rate reserve (%HRR). The ANFIS classifier showed an overall 29.6% difference in classification accuracy and a good balance between sensitivity (90.7%) and specificity (95.2%) on average. With its ease of implementation and variable measurement, the ANFIS classifier shows potential for widespread use by practitioners for work rate assessment. [ABSTRACT FROM AUTHOR]

The pulmonary O2 uptake (...O2p) response to ramp-incremental (RI) exercise increases linearly with work rate (WR) after an early exponential phase, implying that a single time constant (τ) and gain (G) describe the response. However, variability in τ and G of ...O2p kinetics to different step increments in WR is documented. We hypothesized that the "linear" ...O2p-WR relationship during RI exercise results from the conflation between WR-dependent changes in τ and G. Nine men performed three or four repeats of RI exercise (30 W/min) and two step-incremental protocols consisting of four 60-W increments beginning from 20 W or 50 W. During testing, breath-by-breath ...O2p was measured by mass spectrometry and volume turbine. For each individual, the ...O2p RI response was characterized with exponential functions containing either constant or variable τ and G values. A relationship between τ and G vs. WR was determined from the step-incremental protocols to derive the variable model parameters. τ and G increased from 21 ± 5 to 98 ± 20 s and from 8.7 ± 0.6 to 12.0 ±1.9 ml⋅min-1 ⋅W-1 for WRs of 20-230 W, respectively, and were best described by a second-order (τ) and a first-order (G) polynomial function of WR (lowest Akaike information criterion score). The sum of squared residuals was not different (P > 0.05) when the ...O2p RI response was characterized with either the constant or variable models, indicating that they described the response equally well. Results suggest that τ and G increase progressively with WR during RI exercise. Importantly, these relationships may conflate to produce a linear ...O2p-WR response, emphasizing the influence of metabolic heterogeneity in determining the apparent ...O2p-WR relationship during RI exercise. [ABSTRACT FROM AUTHOR]

Purpose: To examine how match performance parameters in trained footballers relate to skeletal muscle parameters, sprint ability and intermittent exercise performance.Methods: 19 male elite football players completed an experimental game with physical performance determined by video analysis and exercise capacity assessed by intermittent Yo-Yo IR1 and IR2 tests, and a repeated sprint test (RST). Muscle tissue was obtained for analysis of metabolic enzyme maximal activity and key muscle protein expression.Results: Total game distance, distance deficit from first to second half and high-intensity running in the final 15 min of the game were all correlated to the players' Yo-Yo IR1 performance (r = 0.55-0.87) and beta-hydroxyacyl-CoA-dehydrogenase (HAD) maximal activity (r = 0.55-0.65). Furthermore, platelet/endothelial cell adhesion molecule-1 (PECAM1) protein expression was weakly (r = 0.46) correlated to total game distance. Peak 5-min game distance faster than 21 km h(-1) was related to the Na(+)-K(+) ATPase subunit (α1, α2, β1 and FXYD1) protein levels (r = 0.54-0.70), while Yo-Yo IR2 performance explained 40 % of the variance in high-intensity game distance. Total and 1-min peak sprint distance correlated to myosin heavy chain II/I ratio (MHCII/I ratio) and sarcoendoplasmic reticulum Ca(2+) ATPase isoform-1 (SERCA1) protein (r = 0.56-0.86), while phosphofructokinase (PFK) maximal activity also correlated to total sprint distance (r = 0.46).Conclusion: The findings emphasize the complexity of parameters predicting physical football performance with Yo-Yo IR1 and HAD as the best predictors of total distance, while high expression of Na(+)-K(+) ATPase proteins and the Yo-Yo IR2 test are better predictors of high-intensity performance. Finally, sprint performance relates to skeletal muscle fiber-type composition. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to examine the effects of external work rate on joint specific power and the relationship between knee extension power and vastus lateralis muscle oxygen consumption (mVO2). We measured kinematics and pedal forces and used inverse dynamics to calculate joint power for the hip, knee and ankle joints during an incremental cycling protocol performed by 21 recreational cyclists. Vastus lateralis mVO2 was estimated using near-infrared spectroscopy with an arterial occlusion. The main finding was a non-linear relationship between vastus lateralis mVO2 and external work rate that was characterised by an increase followed by a tendency for a levelling off (R(2)=0.99 and 0.94 for the quadratic and linear models respectively, p<0.05). When comparing 100W and 225W, there was a ∼43W increase in knee extension but still a ∼9% decrease in relative contribution of knee extension to external work rate resulting from a ∼47W increase in hip extension. When vastus lateralis mVO2 was related to knee extension power, the relationship was still non-linear (R(2)=0.99 and 0.97 for the quadratic and linear models respectively, p<0.05). These results demonstrate a non-linear response in mVO2 relative to a change in external work rate. Relating vastus lateralis mVO2 to knee extension power showed a better fit to a linear equation compared to external work rate, but it is not a straight line. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to examine the influence of intensity, tonnage, rate of fatigue, work rate, rest interval, time underload and session duration on session rating of perceived exertion. The study participants performed a standardized lifting session of five exercises including bench press, leg press and leg curl. The results suggest that sRPE increases with intensity in resistance training with matched tonnage and rest duration between sets.

Purpose. The aim of the study was to establish the respiratory response to unloaded cycling at different cadences. Methods. Eleven healthy participants performed a maximal graded exercise test on a cycle ergometer to assess aerobic fitness (maximal oxygen consumption: 46.27 ± 5.41 ml · min-1 · kg-1) and eight 10-min unloaded pedaling (0 W) bouts at a constant cadence (from 40 to 110 rpm). Respiratory data were measured continuously during each effort and then averaged over 30 s. Blood samples were collected before and 2 min after each effort to monitor changes in acid-base balance. Results. The efforts were performed at an intensity of 16.5-37.5% VO2peak. Respiratory response was not differentiated in cadences of 40, 50, 60 rpm. From 70 rpm, an increase in cadence was significantly associated with increased minute ventilation (F = 168.11, p < 0.000) and oxygen consumption (F = 214.86 p < 0.000) and, from 80 rpm, respiratory frequency (F = 16.06, p < 0.001) and tidal volume (F = 54.67, p < 0.000). No significant changes in acid-base balance were observed as a result of difference cadences. Conclusions. Unloaded cycling at a cadence of 70 rpm or above has a significant effect on respiratory function and may be associated with the involvement of large muscle ergoreceptors (mechanoreceptors) stimulated by the frequency of muscle contractions. [ABSTRACT FROM AUTHOR]

The ability to efficiently utilize metabolic energy to produce work is a key factor for endurance performance. The present study investigated the effects of incline, performance level, and gender on the gross mechanical efficiency during roller ski skating. Thirty-one male and nineteen female elite cross-country skiers performed a 5-min submaximal session at approximately 75% of VO2peak on a 5% inclined treadmill using the G3 skating technique. Thereafter, a 5-min session on a 12% incline using the G2 skating technique was performed at a similar work rate. Gross efficiency was calculated as the external work rate against rolling friction and gravity divided by the metabolic rate using gas exchange. Performance level was determined by the amount of skating FIS points [the Federation of International Skiing (FIS) approved scoring system for ski racing] where fewer points indicate a higher performance level. Strong significant correlations between work rate and metabolic rate within both inclines and gender were revealed (r = -0.89 to 0.98 and P < 0.05 in all cases). Gross efficiency was higher at the steeper incline, both for men (17.1 ± 0.4 vs. 15.8 ± 0.5%, P < 0.05) and women (16.9 ± 0.5 vs. 15.7 ± 0.4%, P < 0.05), but without any gender differences being apparent. Significant correlations between gross efficiency and performance level were found for both inclines and genders (r = -0.65 to 0.81 and P < 0.05 in all cases). The current study demonstrated that cross-country skiers of both genders used less metabolic energy to perform the same amount of work at steeper inclines, and that the better ranked elite male and female skiers skied more efficiently. [ABSTRACT FROM AUTHOR]

The current study simulated cross-country skiing on varying terrain by using a power balance model. By applying the hypothetical inductive deductive method, we compared the simulated position along the track with actual skiing on snow, and calculated the theoretical effect of friction and air drag on skiing performance. As input values in the model, air drag and friction were estimated from the literature, whereas the model included relationships between heart rate, metabolic rate, and work rate based on the treadmill roller-ski testing of an elite cross-country skier. We verified this procedure by testing four models of metabolic rate against experimental data on the treadmill. The experimental data corresponded well with the simulations, with the best fit when work rate was increased on uphill and decreased on downhill terrain. The simulations predicted that skiing time increases by 3%-4% when either friction or air drag increases by 10%. In conclusion, the power balance model was found to be a useful tool for predicting how various factors influence racing performance in cross-country skiing. [ABSTRACT FROM AUTHOR]

This study aimed to establish the nature of lower extremity intra-limb coordination variability in cycling and to investigate the coordinative adaptations that occur in response to changes in cadence and work rate. Six trained and six untrained males performed nine pedalling bouts on a cycle ergometer at various cadences and work rates (60, 90, and 120 revolutions per minute (rpm) at 120, 210, and 300 W). Three-dimensional kinematic data were collected and flexion/extension angles of the ankle, knee, and hip joints were subsequently calculated. These data were used to determine two intra-limb joint couplings [hip flexion/extension–knee flexion/extension (HK) and knee flexion/extension–ankle plantar-flexion/dorsi-flexion (KA)], which were analysed using continuous relative phase analysis. Trained participants displayed significantly (p < 0.05) lower coordination variability (6.6 ± 4.0°) than untrained participants (9.2 ± 4.7°). For the trained subjects, the KA coupling displayed significantly more in-phase motion in the 120 rpm (19.2 ± 12.3°) than the 60 (30 ± 7.1°) or 90 rpm (33.1 ± 7.4°) trials and the HK coupling displayed significantly more in-phase motion in the 90 (33.3 ± 3.4°) and 120 rpm (27.9 ± 13.6°) than in the 60 rpm trial (36.4 ± 3.5°). The results of this study suggest that variability may be detrimental to performance and that a higher cadence is beneficial. However, further study of on-road cycling is necessary before any recommendations can be made. [ABSTRACT FROM PUBLISHER]

This investigation was designed to analyze the time-trial (STT) in an international cross-country skiing sprint skating competition for (1) overall STT performance and relative contributions of time spent in different sections of terrain, (2) work rate and kinematics on uphill terrain, and (3) relationships to physiological and kinematic parameters while treadmill roller ski skating. Total time and times in nine different sections of terrain by 12 world-class male sprint skiers were determined, along with work rate and kinematics for one specific uphill section. In addition, peak oxygen uptake (VO(2peak)), gross efficiency (GE), peak speed (V(peak)), and kinematics in skating were measured. Times on the last two uphill and two final flat sections were correlated to overall STT performance (r = ~-0.80, P < 0.001). For the selected uphill section, speed was correlated to cycle length (r = -0.75, P < 0.01) and the estimated work rate was approximately 160% of peak aerobic power. VO(2peak), GE, V(peak), and peak cycle length were all correlated to STT performance (r = ~-0.85, P < 0.001). More specifically, VO(2peak) and GE were correlated to the last two uphill and two final flat section times, whereas V(peak) and peak cycle length were correlated to times in all uphill, flat, and curved sections except for the initial section (r = ~-0.80, P < 0.01). Performances on uphill and flat terrain in the latter part were the most significant determinants of overall STT performance. Peak oxygen uptake, efficiency, peak speed, and peak cycle length were strongly correlated to overall STT performance, as well as to performance in different sections of the race. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to evaluate aerobic exercise levels, expressed in terms of ventilatory threshold (VT), in a Japanese population and explore the relationship between VT and exercise habits in this population. Methods: This was a cross-sectional study in which data collected from 547 men and 524 women aged 20-69 years and not on medications, were used to assess exercise habits and parameters at VT, namely, oxygen uptake, work rate, and heart rate. Results: Age-related changes in parameters at VT were noted. Of the participants, 205 men (37.5%) and 142 women (27.1%) had exercise habits. Oxygen uptake and work rate at VT in subjects with exercise habits were significantly higher than those without exercise habits after age had been adjusted for in both sexes. Anthropometric parameters were significantly correlated with oxygen uptake at VT, and the highest correlation coefficient rate was found between oxygen uptake at VT and body fat percentage (men r = −0.589, women r = −0.631). Conclusion: The mean values determined here may provide a useful database for evaluating VT in Japanese adult subjects. [ABSTRACT FROM AUTHOR]

The study examines fatigue in elite soccer played in hot conditions. High-profile soccer players ( n=20) were studied during match play at ∼31 °C. Repeated sprint and jump performances were assessed in rested state and after a game and activity profile was examined. Additionally, heart rate (HR), blood lactate, muscle temperature and body mass changes were determined. Repeated sprint and jump performances were reduced ( P<0.05) by 2.6% and 8.2%, respectively, after the game. The fatigue index in the repeated sprint test was 6.0±0.7% after the game compared with 1.7±1.0% at rest ( P<0.05). High-intensity running was 57±4% lower ( P<0.05) during the last 15-min interval of the game compared with the first 15-min period. No differences were observed in mean HR or blood lactates between halves. Muscle temperature was 40.5±0.4 °C after the first half, which was 0.8±0.2 °C higher ( P<0.05) than after the second half. Net fluid loss during the game was >2% of the body mass. Correlations were observed between net-fluid loss and repeated sprint test fatigue index after the game ( r=0.73, P<0.05) and Yo-Yo intermittent recovery, level 1 test performance and high-intensity running during the final 15 min of the game ( r=0.51, P<0.05). The study provides direct evidence of compromised repeated sprint and jump performances induced by soccer match play and pronounced reduction in high-intensity running toward the end of an elite game played in a hot environment. This fatigue could be associated training status and hyperthermia/dehydration. [ABSTRACT FROM AUTHOR]

The present study investigated metabolic rate (MR) and gross efficiency (GE) at moderate and high work rates, and the relationships to gross kinematics and physical characteristics in elite cross-country skiers. Eight world class (WC) and eight national level (NL) male sprint cross-country skiers performed three 5-min stages using the skating G3 technique, whilst roller skiing on a treadmill. GE was calculated by dividing work rate by MR. Work rate was calculated as the sum of power against gravity and frictional rolling forces. MR was calculated using gas exchange and blood lactate values. Gross kinematics, i.e. cycle length (CL) and cycle rate (CR) were measured by video analysis. Furthermore, the skiers were tested for time to exhaustion (TTE), peak oxygen uptake (VO(2peak)), and maximal speed (V(max)) on the treadmill, and maximal strength in the laboratory. Individual performance level in sprint skating was determined by FIS points. WC skiers did not differ in aerobic MR, but showed lower anaerobic MR and higher GE than NL skiers at a given speed (all P < 0.05). Moreover, WC skiers skated with longer CL and had higher V(max) and TTE (all P < 0.05). In conclusion, the present study shows that WC skiers are more efficient than NL skiers, and it is proposed that this might be due to a better technique and to technique-specific power. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of match location, quality of opposition, and match status on distance covered at various speeds in elite soccer. Twenty-seven Spanish Premier League matches played by a professional soccer team were monitored in the 2005-2006 season using a multiple-camera match analysis system. The dependent variables were the distance covered by players at different intensities. Data were analysed using a linear regression analysis with three independent variables: match status (i.e. whether the team was winning, losing or drawing), match location (i.e. playing at home or away), and quality of the opponents (strong or weak). The top-class players performed less high-intensity activity (>19.1 km · h-1) when winning than when they losing, but more distance was covered by walking and jogging when winning. For each minute winning, the distance covered at submaximal or maximal intensities decreased by 1 m (P<0.05) compared with each minute losing. For each minute winning, the distance covered by walking and jogging increased by 2.1 m (P<0.05) compared with each minute losing. The home teams covered a greater distance than away teams during low-intensity activity (<14.1 km · h-1) (P<0.01). Finally, the better the quality of the opponent, the higher the distance covered by walking and jogging. Our findings emphasize the need for match analysts and coaches to consider the independent and interactive effects of match location, quality of opposition, and match status during assessment of the physical component of football performance. [ABSTRACT FROM AUTHOR]

Abstract: Soccer referees are required to keep up with play at all times despite occupying an age bracket of on average 10–15 years older than their playing counterparts. Therefore, the aim of the present study was to examine the effect of age upon the physical match performances and match physiological loads of elite-level soccer referees. Match analysis data was collected (Prozone®, Leeds, UK) from 22 professional soccer referees (age range 31–48 years) on FA Premier League matches over four consecutive seasons (778 observations). Physical match performance categories were total-distance covered (TD); high intensity running distance (speed >5.5ms−1, HIR); sprint count (>7.0ms−1, SC); top sprinting speed (TS); average distance from the ball (DB) and average distance from fouls (DF). Significant age effects were found for TD (r =−0.52, p <0.001), HIR (r =−0.53, p <0.001) and SC (r =−0.53, p <0.001). No age effect was found for DB and DF (p >0.05). Despite covering less TD, HIR and performing fewer sprints the older referees (43–48 years) were able to maintain an average distance from fouls that was comparable to that recorded by the young (31–36 years) referees. Therefore, the reduced physical match performances associated with increasing referee age did not appear to impact upon the older referees’ ability to keep up with play. In light of these findings, refereeing governing bodies may wish to review their age-based retirement guidelines. [Copyright &y& Elsevier]

We focus on the effect of cadence and work rate on energy expenditure and efficiency in cycling, and present arguments to support the contention that gross efficiency can be considered to be the most relevant expression of efficiency. A linear relationship between work rate and energy expenditure appears to be a rather consistent outcome among the various studies considered in this review, irrespective of subject performance level. This relationship is an example of the Fenn effect, described more than 80 years ago for muscle contraction. About 91% of all variance in energy expenditure can be explained by work rate, with only about 10% being explained by cadence. Gross efficiency is strongly dependent on work rate, mainly because of the diminishing effect of the (zero work-rate) base-line energy expenditure with increasing work rate. The finding that elite athletes have a higher gross efficiency than lower-level performers may largely be explained by this phenomenon. However, no firm conclusions can be drawn about the energetically optimal cadence for cycling because of the multiple factors associated with cadence that affect energy expenditure. [ABSTRACT FROM AUTHOR]