Urea production during prolonged swimming

Male interscholastic swimmers (n = 8) completed a 4572 m training swim in 62 ±1.1 min (x ± s.e.) with terminal heart rate and blood lactate of 152 ± 6 beats min^‐1 and 6.9±0.89 mM, respectively. Sweat rate (0.48±0.0951. h^‐1) was lower than similar intensity cycling (1.5±0.13 1. h^‐1) or running (1.1 ± 0.14 l.h^‐1). Post‐swim serum urea N (11.6±0.71 mM) was elevated (P<0.05) vs pre‐swim (4.6±0.39 mM). Post‐swim urine volume (860±75 ml 24 h^‐1) was reduced (P<0.07) and resulted in an elevated (P<0.05), but delayed (24–84 h), post‐exercise urea N excretion. Although the reduced urine and sweat production during the swim undoubtedly contributed to the elevated serum urea, there must be another explanation because together they could only account for 38% of the observed increase. On the basis of the magnitude of serum urea increase, it appears that the swim caused an increase in urea production (amino acid oxidation). The failure to observe larger increases in urinary urea during recovery indicates that either urea excretion following exercise continues for prolonged periods of time (>48 h) or another significant mode of nitrogen excretion exists.     

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Thigh muscle volume is a useful determinant of functional fitness. However, anthropometric prediction of muscle content is influenced by the variability of adipose tissue accumulation. The aims of this study were to predict thigh muscle and adipose tissue volumes from anthropometry and to assess the validity of the method by examining the various components of the measurements and the assumptions involved. The 19 participants (9 men, 10 women; age 23-49 years) varied in adiposity. They all underwent magnetic resonance imaging (MRI) of the upper leg and the eight men and two women with the lowest adiposity underwent detailed anthropometry involving girths and skinfolds. Using MRI as the reference method, muscle volume was predicted from anthropometry using a circular concentric model, and the assumptions inherent in the method were tested further using the MRI data alone. Muscle volume was best predicted by anthropometry in the 10 leanest participants using a five-slice truncated cone model that overestimated the mean MRI value by 30% ( R 2 = 0.95; standard error of estimate = 288 cm 3 ; P ? 0.001). A single skinfold plus girth measurement at the mid-thigh almost matched its predictive ability, but with an increased bias. Measurements of leg circumference by means of the two techniques agreed well. The assumption of a circular cross-section was valid. In contrast, the agreement between skinfold thickness measured by caliper and superficial adipose tissue thickness by MRI was poor, contributing to the scatter of fat and lean area comparisons. An anterior skinfold thickness measurement underestimated the area of superficial adipose tissue at that level, particularly at the most proximal and distal sites. Although these limitations increase the uncertainties of muscle volume determination by anthropometry, they do not prevent its valid prediction in leaner individuals. The prediction of superficial adipose tissue was poorer.     

Physiological demands of top-class soccer refereeing in relation to physical capacity: effect of intense intermittent exercise training

To examine the activity profile and physiological demands of top-class soccer refereeing, we performed computerized time-motion analyses and measured the heart rate and blood lactate concentration of 27 referees during 43 competitive matches in the two top Danish leagues. To relate match performance to physical capacity and training, several physiological tests were performed before and after intermittent exercise training. Total distance covered was 10.07 - 0.13 km (mean - s x ), of which 1.67 - 0.08 km was high-intensity running. High-intensity running and backwards running decreased (P ? 0.05) in the second half. Mean heart rate was 162 - 2 beats· min -1 (85 - 1% of maximal heart rate) and the mean blood lactate concentration was 4.9 - 0.3 (range 1.7-14.0) mmol·l -1 . The amount of high-intensity running during a match was related to the Yo-Yo intermittent recovery test ( r 2 = 0.57; P ? 0.05) and the 12 min run ( r 2 = 0.21; P ? 0.05). After intermittent training ( n = 8), distance covered during high-intensity running was greater (2.06 - 0.13 vs 1.69 - 0.08 km; P ? 0.05) and mean heart rate was lower (159 - 1 vs 164 - 2 beats· min -1 ; P ? 0.05) than before training. The results of the present study demonstrate that: (1) top-class soccer referees have significant aerobic energy expenditure throughout a game and episodes of considerable anaerobic energy turnover; (2) the ability to perform high-intensity running is reduced towards the end of matches; (3) the Yo-Yo intermittent recovery test can be used to evaluate referees' match performance; and (4) intense intermittent exercise training improves referees' performance capacity during a game.     

Confirmatory factor analysis of the Test of Performance Strategies (TOPS) among adolescent athletes

The aim of the present study was to examine the factorial validity of the Test of Performance Strategies (TOPS; Thomas et al., ) among adolescent athletes using confirmatory factor analysis. The TOPS was designed to assess eight psychological strategies used in competition (i.e. activation, automaticity, emotional control, goal-setting, imagery, negative thinking, relaxation and self-talk,) and eight used in practice (the same strategies except negative thinking is replaced by attentional control). National-level athletes (n?=?584) completed the 64-item TOPS during training camps. Fit indices provided partial support for the overall measurement model for the competition items (robust comparative fit index?=?0.92, Tucker-Lewis index?=?0.88, root mean square error of approximation?=?0.05) but minimal support for the training items (robust comparative fit index?=?0.86, Tucker-Lewis index?=?0.81, root mean square error of approximation?=?0.06). For the competition items, the automaticity, goal-setting, relaxation and self-talk scales showed good fit, whereas the activation, emotional control, imagery and negative thinking scales did not. For the practice items, the attentional control, emotional control, goal-setting, imagery and self-talk scales showed good fit, whereas the activation, automaticity and relaxation scales did not. Overall, it appears that the factorial validity of the TOPS for use with adolescents is questionable at present and further development is required.     

Interpretation and application of the offside law by expert assistant referees: Perception of spatial positions in complex dynamic events on and off the field

Abstract

Baldo et al. (2002 Baldo, M. V. C., Ranvaud, R. D. and Morya, E. 2002. Flag errors in soccer games: The flash-lag effect brought to real life. Perception, 31: 1205–1210. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and Helsen et al. (2006 Helsen, W., Gilis, B. and Weston, M. 2006. Errors in judging “offside” in association football: Test of the optical error versus the perceptual flash-lag hypothesis. Journal of Sports Sciences, 24: 521–528. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) considered the flash-lag effect to explain errors made by assistant referees when judging offside in association football. The main aims of the present study were as follows: (1) to determine whether the flash-lag effect emerges in offside situations on the field of play or off the field when presented as computer animations or as video footage of real-life matches; (2) to examine offside decision-making errors in two standards of assistant referee – international FIFA and Belgian national referees. The results support the flash-lag hypothesis in several ways. First, both the FIFA and Belgian assistant referees were more likely to make errors by raising their flag when they had to assess offside situations on the field of play and when presented as three-a-side computer animations. Second, more flag errors were made when the defender moved in the opposite direction to that of the attacker. Third, the strategy of raising the flag in case of doubt was not observed when an interpretation of the offside law had to be made about the involvement of play of an attacker. Future research is needed to examine the extent to which on- and off-the-field training sessions can be used as training tools to improve offside decision-making.     

A protocol for measuring the direct effect of cycling on neuromuscular control of running in triathletes

Abstract

The direct effects of cycling on movement and muscle recruitment patterns (neuromuscular control) during running are unknown but critical to success in triathlon. We outline and test a new protocol for investigating the direct influence of cycling on neuromuscular control during running. Leg movement (three-dimensional kinematics) and muscle recruitment (surface electromyography, EMG) were compared between a control run (no prior exercise) and a 30-min transition run that was preceded by 20 min of cycling. We conducted three experiments investigating: (a) the repeatability (between-day reliability) of the protocol; (b) the ability of the protocol to investigate, in highly trained national or international triathletes, the direct influence of cycling on neuromuscular control during running independent of neuromuscular fatigue; and (c) the ability of the protocol to provide a control, or baseline, measure of neuromuscular control (determined using a measure of stability) without causing fatigue. Kinematic and EMG measures of neuromuscular control during running showed moderate to high repeatability: mean coefficients of multiple correlation for repeatability of EMG and kinematics were 0.816 ± 0.014 and 0.911 ± 0.031, respectively. The protocol provided a robust baseline measure of neuromuscular control during running without causing neuromuscular fatigue (coefficients of multiple correlation for stability of EMG and kinematics were 0.827 ± 0.023 and 0.862 ± 0.054), while EMG and force data provided no evidence of fatigue. The protocol outlined here is repeatable and can be used to measure any direct influence of cycling on neuromuscular control during running.     

The reliability and validity of the bar-mounted PUSH BandTM 2.0 during bench press with moderate and heavy loads

ABSTRACT

The aim of this study was to assess the reliability and validity of the bar-mounted PUSH Band^TM 2.0 to determine peak and mean velocity during the bench press exercise with a moderate (60% one repetition maximum [1RM]) and heavy (90% 1RM) load. We did this by simultaneously recording peak and mean velocity using the PUSH Band^TM 2.0 and three-dimensional motion capture from participants bench pressing with 60% and 90% 1RM. We used ordinary least products regression to assess within-session reliability and whether the PUSH Band^TM 2.0 could accurately predict motion capture velocity. Results showed that PUSH Band^TM 2.0 and motion capture peak and mean velocity reliability was acceptable with both loads. While there was a tendency for the PUSH Band^TM 2.0 to slightly overestimate peak and mean velocity, there was no fixed bias. However, mean velocity with 60 and 90% 1RM demonstrated proportional bias (differences between predicted and motion capture values increase with magnitude). Therefore, PUSH Band^TM 2.0 peak velocity with 60 and 90% 1RM is valid, but mean velocity is not.     

Exercise training increases the S-Klotho plasma levels in sedentary middle-aged adults: A randomised controlled trial. The FIT-AGEING study

ABSTRACT

This study aimed to investigate the effects of different training modalities on the soluble Klotho (S-Klotho) plasma levels in sedentary middle-aged adults. A total of 74 middle-aged adults (53.4 ± 5.0 years old; 52.7% women) were enrolled in the FIT-AGEING study. We conducted a 12-week randomised controlled trial. The participants were randomly assigned to 4 different groups: (i) a control group (no exercise), (ii) a physical activity recommendation from the World Health Organization group (PAR), (iii) a high intensity interval training group (HIIT), and (iv) a high intensity interval training group adding whole-body electromyostimulation training group (HIIT-EMS). S-Klotho plasma levels, anthropometric measurements, and body composition variables were measured before and after the intervention programme. All exercise training modalities induced an increase in the S-Klotho plasma levels (all P ≤ 0.019) without statistical differences between them (all P ≥ 0.696). We found a positive association between changes in lean mass index and changes in the S-Klotho plasma levels, whereas a negative association was reported between changes in fat mass outcomes and changes in the S-Klotho plasma levels after our intervention study. In conclusion, our results suggest that the link between exercise training and the increase in S-Klotho plasma levels could be mediated by a decrease of fat mass and an increase of lean mass.     

The Impact of an Obstacle Course Sport Education Season on Students' Aerobic Fitness Levels

Abstract

The purpose of this study was to determine if factor patterns of selected sports skills were similar for two samples, a skilled sample and one consisting of a wide range of skills. Comparisons were also made with kinesiological evidence regarding the patterning of basic sports skills. Data consisting of performance scores on various sports skills were available for 166 high school girls. Out of this sample, a smaller sample was drawn consisting of 69 girls who were above average in skill. Two factor models, alpha and incomplete image analysis, were used in the analysis of this data. The factor pattern of selected sports skills performed by subjects above average in skill was similar in many respects to that of a sample which included a wide range of skill. The primary difference lay in the clustering of overarm skills which appeared in the above-average factor pattern. The overarm and push patterns of the above-average sample resembled the patterns of skill obtained through kinesiological analysis. The structure of kicking, underarm, and sidearm skills remained obscure, based on the results of factor analytic techniques.     

The Development of Skill and Knowledge During a Sport Education Season of Track and Field Athletics

Purpose: The purpose of this study was to examine the relative effectiveness of 2 forms of physical education instruction on students' skill and technical performance, as well as content knowledge in 3 track and field events. Method: Students from 6 classes in 3 Portuguese schools completed 900-min units conducted under the auspices of sport education or a more traditional teacher-directed format. Classes were randomly assigned to these conditions within each school. Results: Although both groups improved significantly from pretest to posttest, the sport education classes outperformed the traditional classes in both technique and skill execution. Only the sport education group made significant improvements in content knowledge. When the students in the traditional group were tested at the point in time where they would usually complete a unit of physical education (450 min), there were no significant improvements in any of the study's variables. Conclusion: The explanation given for the superior performance outcomes of the sport education classes lies in the nature of formal competition and team affiliation, which are cornerstones of this pedagogical model. That is, students take their learning experiences more seriously than in traditional and often inauthentic classes. In terms of content knowledge, the fact that sport education has a level of content-embedded accountability that holds students accountable for their officiating duties is postulated as a significant contributor to their increased understanding of rules and protocols of athletic events.