The geometric curvature of the spine during the sirshasana,the yoga’s headstand

This study analysed the behaviour of the geometric curvature of the spine during sirshasana. The position of dorsal retroreflective markers was computed via stereophotogrammetric analysis in six males and five females (29.4 ± 8.8 years, 63.0 ± 11.4 kg, 1.66 ± 0.08 m [average ± standard deviation]). The spinal points were projected onto the sagittal and frontal planes of the trunk, a polynomial was fitted to the data and the two-dimensional geometric curvature was quantified. The inferior lumbar lordosis decreased compared to the orthostatic position and gait, which may favour the posterior protrusion of the lumbar spinal nucleus pulposus in people with posterior herniation. The lateral deviation at the middle of the thoracic spine increases during sirshasana, which may reflect increased difficulties for postural control and spinal loads. It could be useful for promoting positive spinal structural and functional chronic adaptations for healthy participants, if the yoga programme is carefully planned and the spinal alignment is carefully monitored during a headstand. However, it may aggravate some spinal diseases, especially scoliosis.     

Effects of consecutive days of match play on technical performance in tennis

Elite tennis is characterised by repeated bouts of up to 5-set match play, yet little is known about the technical requirements of shots played. This study therefore investigated technical performance changes over consecutive days of prolonged, simulated tennis match play. A total of 7 well-trained men tennis players performed 4 consecutive days of competitive 4-h match play. Matches were notated to determine between-day changes in groundstroke and serve performance, as well as point and match durations. Changes ≥75% likely to exceed the smallest important effect size (0.2) were considered meaningful and represented as effect size ± 90% confidence interval. Effective playing time reduced on days 3 and 4, alongside likely increases in “stretch” groundstrokes over the 4 days (mean effect size ± 90% confidence interval; 0.57 ± 0.38) and “stretch” backhand returns on days 2 and 3 (0.39 ± 0.54 and 0.67 ± 0.55). Relative unforced errors increased on day 4 (vs. day 2; 0.36 ± 0.22) and second-serve winning percentage reduced after day 1 (?0.47 ± 0.50). Further, a likely increase in emotional outbursts characterised day 3 (vs. day 2; 0.73 ± 0.57). Consecutive-day match play impairs hitting accuracy, stroke positioning and emotional responses; an understanding of which prepares players for elite-standard tennis tournament play.     

A Sport Education Fitness Season’s Impact on Students’ Fitness Levels,Knowledge, and In-Class Physical Activity

Purpose: The purpose of this study was to determine the extent to which a sport education season of fitness could provide students with recommended levels of in-class moderate-to-vigorous physical activity (MVPA) while also increasing students’ fitness knowledge and fitness achievement. Method: One hundred and sixty-six 5th-grade students (76 boys, 90 girls) participated in a 20-lesson season called “CrossFit Challenge” during a 4-week period. The Progressive Aerobic Cardiovascular Endurance Run, push-ups, and curl-ups tests of the FITNESSGRAM® were used to assess fitness at pretest and posttest, while fitness knowledge was assessed through a validated, grade-appropriate test of health-related fitness knowledge (HRF). Physical activity was measured with Actigraph GT3X triaxial accelerometers. Results: Results indicated a significant time effect for all fitness tests and the knowledge test. Across the entire season, the students spent an average of 54.5% of lesson time engaged in MVPA, irrespective of the type of lesson (instruction, free practice, or competition). Conclusions: The results suggest that configuring the key principles of sport education within a unit of fitness is an efficient model for providing students with the opportunity to improve fitness skill and HRF knowledge while attaining recommended levels of MVPA.     

Laboratory predictors of uphill cycling performance in trained cyclists

ABSTRACT

This study aimed to assess the relationship between an uphill time-trial (TT) performance and both aerobic and anaerobic parameters obtained from laboratory tests. Fifteen cyclists performed a Wingate anaerobic test, a graded exercise test (GXT) and a field-based 20-min TT with 2.7% mean gradient. After a 5-week non-supervised training period, 10 of them performed a second TT for analysis of pacing reproducibility. Stepwise multiple regressions demonstrated that 91% of TT mean power output variation (W kg^?1) could be explained by peak oxygen uptake (ml kg^?1.min^?1) and the respiratory compensation point (W kg^?1), with standardised beta coefficients of 0.64 and 0.39, respectively. The agreement between mean power output and power at respiratory compensation point showed a bias ± random error of 16.2 ± 51.8 W or 5.7 ± 19.7%. One-way repeated-measures analysis of variance revealed a significant effect of the time interval (123.1 ± 8.7; 97.8 ± 1.2 and 94.0 ± 7.2% of mean power output, for epochs 0–2, 2–18 and 18–20 min, respectively; P < 0.001), characterising a positive pacing profile. This study indicates that an uphill, 20-min TT-type performance is correlated to aerobic physiological GXT variables and that cyclists adopt reproducible pacing strategies when they are tested 5 weeks apart (coefficients of variation of 6.3; 1 and 4%, for 0–2, 2–18 and 18–20 min, respectively).     

Validity of a portable force platform for assessing biomechanical parameters in three different tasks

The aim of this study was to determine the precision and accuracy of the vertical and anterior–posterior force components of the portable PASCO PS-2142 force plate. Impulse, peak force, and time to peak force were assessed and compared to a gold standard force plate in three different tasks: vertical jump, forward jump, and sprint start. Two healthy male participants performed ten trials for each task, resulting in 60 trials. Data analyses revealed good precision and accuracy for the vertical component of the portable force plate, with relative bias and root mean square (RMS) error values nearly the same in all tasks for the impulse, time to peak force, and peak force parameters. Precision and accuracy of the anterior–posterior component were lower for the impulse and time to peak force, with relative bias and RMS error values nearly the same between tasks. Despite the lower precision and accuracy of the anterior–posterior component of the portable force plate, these errors were systematic, reflecting a good repeatability of the measure. In addition, all variables presented good agreement between the portable and gold standard platforms. Our results provide a good perspective for using the aforementioned portable force plate in sports and clinical biomechanics.     

Horizontal ground reaction forces to stationary running performed in the water and on dry land at different physiological intensities

The aim of the present study was to compare the peak anterior–posterior (Fy) and medio–lateral (Fx) ground reaction forces (GRFs) of women performing stationary running at different intensities in aquatic and dry land environments. Fourteen young women performed the stationary running exercise at three cadences (first ventilatory threshold, second ventilatory threshold and maximum effort, as determined during exercise in water) in aquatic and dry land environments. Two-way repeated measures ANOVA was used to analyse the data (α?=?.05). As a result, significantly lower peak Fy anterior, Fy posterior, Fx medial and Fx lateral values were observed for the aquatic environment, except for the Fy posterior at the first ventilatory threshold. Significant differences were observed between cadences in the peak Fy anterior, Fy posterior, Fx medial and Fx lateral values, with higher values for the cadence corresponding to maximum effort compared to the first ventilatory threshold, except for the Fy posterior and Fx medial in the aquatic environment. The results indicate that the horizontal GRFs are reduced in the aquatic environment and depend on the intensity of stationary running exercise performance.     

Book reviews

International Review of Education -