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.     

Dietary supplements

For the athlete training hard, nutritional supplements are often seen as promoting adaptations to training, allowing more consistent and intensive training by promoting recovery between training sessions, reducing interruptions to training because of illness or injury, and enhancing competitive performance. Surveys show that the prevalence of supplement use is widespread among sportsmen and women, but the use of few of these products is supported by a sound research base and some may even be harmful to the athlete. Special sports foods, including energy bars and sports drinks, have a real role to play, and some protein supplements and meal replacements may also be useful in some circumstances. Where there is a demonstrated deficiency of an essential nutrient, an increased intake from food or from supplementation may help, but many athletes ignore the need for caution in supplement use and take supplements in doses that are not necessary or may even be harmful. Some supplements do offer the prospect of improved performance; these include creatine, caffeine, bicarbonate and, perhaps, a very few others. There is no evidence that prohormones such as androstenedione are effective in enhancing muscle mass or strength, and these prohormones may result in negative health consequences, as well as positive drug tests. Contamination of supplements that may cause an athlete to fail a doping test is widespread.     

Running economy,mechanics, and marathon racing shoes

ABSTRACT

The choice of marathon racing shoes can greatly affect performance. The purpose of this study is to metabolically and mechanically compare the consumer version of the Nike Vaporfly 4% shoe to two other popular marathon shoes, and determine differences in running economy. Nineteen subjects performed two 5-minute trials at 4.44m/s wearing the Adidas Adios Boost (AB), Nike Zoom Streak (ZS), and Nike Vaporfly 4% (VP) in random order. Oxygen uptake was recorded during minutes 3–5 and averaged across both shoe trials. On a second day, subjects wore reflective markers, and performed a 3-minute trial in each shoe. Motion and force data were collected over the final 30 seconds of each trial. VP oxygen uptake was 2.8% and 1.9% lower than the AB and ZS. Stride length, plantar flexion velocity, and center of mass vertical oscillation were significantly different in the VP. The percent benefit of the VP over AB shoe was predicted by subject ground time. These results indicate that use of the VP shoe results in improved running economy, partially due to differences in running mechanics. Subject variation in running economy improvement is only partially explained by variation in ground time.     

Effects of agonist–antagonist complex resistance training on upper body strength and power development

Abstract

The objective of this study was to examine the chronic effects on strength and power of performing complex versus traditional set training over eight weeks. Fifteen trained males were assessed for throw height, peak velocity, and peak power in the bench press throw and one-repetition maximum (1-RM) in the bench press and bench pull exercises, before and after the eight-week programme. The traditional set group performed the pulling before the pushing exercise sets, whereas the complex set group alternated pulling and pushing sets. The complex set training sessions were completed in approximately half the time. Electromyographic (EMG) activity was monitored during both test sessions in an attempt to determine if it was affected as a result of the training programme. Although there were no differences in the dependent variables between the two conditions, bench pull and bench press 1-RM increased significantly under the complex set condition and peak power increased significantly under the traditional set condition. Effect size statistics suggested that the complex set was more time-efficient than the traditional set condition with respect to development of 1-RM bench pull and bench press, peak velocity and peak power. The EMG activity was not affected. Complex set training would appear to be an effective method of exercise with respect to efficiency and strength development.     

Memory for Preselected and Constrained Short Movements

Abstract

The present experiment investigated the recall of terminal location and distance of both preselected and constrained short movements (12 cm ± 4 cm approximately) following 5 second and 30 second unfilled retention intervals. Systematic alteration of the magnitude and direction of the starting position for recall movements revealed that the distance moved markedly interfered with the recall of the terminal location, but distance was essentially recalled independently of terminal location. Recall of distance was superior to terminal location for both the unfilled retention intervals, and there was a decrease in location recall performances following the longer 30 second delay when compared to recall attempts after the shorter 5 second delay. The Findings are discussed in terms of recent proposals to account for the memory for, and control of, discrete limb movements.     

Psychological Mood Profiles of Sighted and Unsighted Beep Baseball Players

Purpose: Decline of motor performance in older individuals affects their quality of life. Understanding the contribution of sport-related training in advanced ages might help to attenuate motor performance decay as one gets older. The purpose of our study was to evaluate the extent to which long-lasting training in running or sport-specific skills during old age preserves motor performance in different motor tasks. Method: Older runners and tennis players with at least 10 years of training were assessed as were age-matched and young exercisers. Performance was evaluated for 6 motor tasks requiring different functions of sensorimotor control expected to decline with aging. Results: Analysis revealed that runners had increased aerobic fitness in comparison with the other older participants and that they presented similar performance to older exercisers in the motor tasks. Tennis players outperformed the other groups of older participants on coincident timing and simple reaction time and achieved similar performance to the young group on the timing task. Conclusions: These results suggest selective maintenance of task-specific processing through extensive practice of tennis-related motor skills in older adults.     

High-intensity interval running is perceived to be more enjoyable than moderate-intensity continuous exercise: Implications for exercise adherence

Abstract

The aim of this study was to objectively quantify ratings of perceived enjoyment using the Physical Activity Enjoyment Scale following high-intensity interval running versus moderate-intensity continuous running. Eight recreationally active men performed two running protocols consisting of high-intensity interval running (6×3 min at 90% [Vdot]O_2max interspersed with 6×3 min active recovery at 50% [Vdot]O_2max with a 7-min warm-up and cool down at 70% [Vdot]O_2max) or 50 min moderate-intensity continuous running at 70% [Vdot]O_2max. Ratings of perceived enjoyment after exercise were higher (P < 0.05) following interval running compared with continuous running (88 ± 6 vs. 61 ± 12) despite higher (P < 0.05) ratings of perceived exertion (14 ± 1 vs. 13 ± 1). There was no difference (P < 0.05) in average heart rate (88 ± 3 vs. 87 ± 3% maximum heart rate), average [Vdot]O₂ (71 ± 6 vs. 73 ± 4%[Vdot]O_2max), total [Vdot]O₂ (162 ± 16 vs. 166 ± 27 L) or energy expenditure (811 ± 83 vs. 832 ± 136 kcal) between protocols. The greater enjoyment associated with high-intensity interval running may be relevant for improving exercise adherence, since running is a low-cost exercise intervention requiring no exercise equipment and similar relative exercise intensities have previously induced health benefits in patient populations.     

The Effects of a Group Contingency Strategy on Behaviorally Disordered Students in Physical Education

Abstract

An A-B-A-B time-series design was used to determine the effectiveness of a group contingency strategy in modifying on-task behavior of behaviorally disordered students in a physical education setting. A younger group (n = 12) with a mean age of 7.8 years, and an older group (n = 11) with a mean age of 11.2 years, participated in a study in which activity reinforcement for each group was contingent upon correct observation of the rules established for class. The group contingency strategy was significantly effective in increasing the percentage of on-task behavior of both groups of students. In addition, there was no significant difference in the response to treatment between younger and older students, and there were no individuals within either group who did not respond favorably to treatment.