Matthew Sedgwick

Effect of repeated sprints on postprandial endothelial function and triacylglycerol concentrations in adolescent boys

Abstract This study investigated whether repeated, very short duration sprints influenced endothelial function (indicated by flow-mediated dilation) and triacylglycerol concentrations following the ingestion of high-fat meals in adolescent boys. Nine adolescent boys completed two, 2-day main trials (control and exercise), in a counter-balanced, cross-over design. Participants were inactive on day 1 of the control trial but completed 40 × 6 s maximal cycle sprints on day 1 of the exercise trial. On day 2, capillary blood samples were collected and flow-mediated dilation measured prior to, and following, ingestion of a high-fat breakfast and lunch. Fasting flow-mediated dilation and plasma triacylglycerol concentration were similar in the control and exercise trial (P > 0.05). In the control trial, flow-mediated dilation was reduced by 20% and 27% following the high-fat breakfast and lunch; following exercise these reductions were negated (main effect trial, P < 0.05; interaction effect trial × time, P < 0.05). The total area under the plasma triacylglycerol concentration versus time curve was 13% lower on day 2 in the exercise trial compared to the control trial (8.65 (0.97) vs. 9.92 (1.16) mmol · l−1 · 6.5 h, P < 0.05). These results demonstrate that repeated 6 s maximal cycle sprints can have beneficial effects on postprandial endothelial function and triacylglycerol concentrations in adolescent boys.

Effect of exercise on postprandial endothelial function in adolescent boys.

The ingestion of high-fat meals induces a state of endothelial dysfunction in adults. This dysfunction is attenuated by prior exercise. The response of young people to these nutritional and physiological stressors has not been established. Thus, the purpose of the present study was to investigate if a bout of moderate-intensity exercise influenced endothelial function (as indicated by flow-mediated dilation (FMD)) following the ingestion of a high-fat breakfast and lunch in adolescent boys (aged 12·6-14·3 years). Two, 2 d main trials (control and exercise) were completed by thirteen adolescent boys in a counter-balanced, cross-over design. Participants were inactive on day 1 of the control trial, but completed 60 min of walking at 60 % peak oxygen uptake in the exercise trial. On day 2, endothelial function was assessed via FMD prior to, and following, ingestion of a high-fat breakfast and lunch. There was no difference in fasting FMD between the control and exercise trial (P= 0·449). In the control trial, FMD was reduced by 32 % following consumption of the high-fat breakfast and by 24 % following lunch. In the exercise trial, the corresponding reductions were 6 and 10 %, respectively (main effect trial, P= 0·002). These results demonstrate that moderate-intensity exercise can attenuate the decline in FMD seen following the consumption of high-fat meals in adolescent boys.

Effect of the Great Activity Programme on healthy lifestyle behaviours in 7–11 year olds

Abstract The study investigated the effect of a school-based healthy lifestyles intervention on physical activity and dietary variables. In total 378 children (177 intervention, 201 control; age 9.75 ± 0.82 years (mean ± s)) took part in the 7-month intervention comprising: preparation for and participation in 3 highlight events (a dance festival, a walking event and a running event); an interactive website for pupils, teachers and parents; and vacation activity planners. Primary outcome measures were objectively measured physical activity (pedometers and accelerometers), endurance fitness and dietary variables. Multi-level modelling was employed for data analysis. The increase in physical activity was greater in the intervention group than the control group (steps: 1049 vs 632 daily steps each month; moderate to vigorous physical activity (MVPA) total: 4.6 min · day−1 · month−1 vs 1.3 min · day−1 · month−1; MVPA bouts: 5.4 min · day−1 · month−1 vs 2.6 min · day−1 · month−1; all P < 0.05). The increase in multi-stage fitness test distance was greater for intervention participants (46 vs 29 m · month−1 of intervention, group × month interaction, P < 0.05). There were no differences between groups in dietary variables, body composition, knowledge of healthy lifestyles or psychological variables. Thus an intervention centred around highlight events and including relatively few additional resources can impact positively on the objectively measured physical activity of children.

The accumulation of exercise and postprandial endothelial function in boys

The purpose of this study was to investigate the effect of accumulating 60 min of exercise on endothelial function and triacylglycerol concentrations following the ingestion of a high‐fat breakfast and lunch in 14 adolescent boys (aged 12 to 14 years). Two, 2‐day main trials (control and exercise) were completed in a counter‐balanced, cross‐over design. Participants were inactive on day 1 of the control trial but on day 1 of the exercise trial completed 6 × 10 min runs at 70% of peak oxygen uptake, spread over the day. On day 2, triacylglycerol concentrations and flow‐mediated dilation (FMD) were measured prior to, and following, ingestion of the high‐fat meals. In the control trial, FMD was reduced by 30% and 33% (P < 0.001) following the high‐fat breakfast and lunch; following exercise these reductions were negated (main effect trial, P = 0.002, interaction effect trial × time, P < 0.001). The total and incremental areas under the triacylglycerol concentration vs time curve were reduced by 11% and 16% in the exercise trial; however, these differences were not significant (P > 0.05). These results support the concept of accumulating physical activity for health in adolescents as the accumulated exercise attenuated the decline in FMD seen following the consumption of high‐fat meals.

The relative age effect

The Relative Age Effect (RAE) is a phenomenon that suggests that athletes at elite level are more likely to be born in the first 3 months after the eligibility cut-off date for a particular age group in sports. For example, with sports, such as football, which generally use a cut-off date of January 1st (any player born in 1998 is eligible to play at Under 15 level for the season beginning in 2013) players who compete at elite level of under-age sport are substantially more likely to be born in the months of January, February and March. Similarly if the cut-off date is July 1st then the likelihood of elite players being born in July, August and September increases dramatically. It has been shown that a change in eligibility cut-off date only serves to adjust the RAE to the months following the new date (Butler D; Butler R & Sherman M).Recently, it has been suggested that movement variability –particularly coordination variability – can be functional in reducing the risk of injury. Pollard et al. (2005: Journal of Applied Biomechanics, 21, 143 – 152) reported that females demonstrate lower coordination variability than males during performance of an unanticipated cutting movement. Furthermore, a history of lower extremity injury has been shown to effect lower extremity coordination variability during running (Heiderscheit et al., 2002: Journal of Applied Biomechanics, 18, 110 – 121). Therefore, the purpose of this study was to evaluate both the effect of gender and history of ACL injury on lower extremity joint coupling variability during performance of an unanticipated cutting technique. With approval from the University’s ethics committee, 8 female basketball players (age 21.6 +1.41 years, height 1.70 +0.08 m, mass 64.6 +7.3 kg), 8 male basketball players (age 22.9+ 2.95, height 1.90 +0.19 m, mass 77.1 + 11.7 kg) and 6 additional female basketball players with a history of unilateral ACL reconstruction (ACLr; age Abstracts S21 29.4 + 8.92 years, height 1.70 +0.05 m, mass 67.5 + 9.62 kg) provided written, informed consent. During performance of seven unanticipated cutting tasks, three-dimensional joint and segment kinematics were recorded using an eight digital-camera motion capture system (Motion Analysis Corp.,Santa Rosa, CA, USA) sampling at 240 Hz. Between groups differences in joint and segment coupling variability were evaluated with between group ANOVAs. Furthermore, the explained variance (Z2) for each joint coupling was calculated to demonstrate the magnitude of differences between the three groups. In support of Pollard et al. (2005), females demonstrated reduced variability in two joint couplings (hip abduction-adduction/knee rotation variability (P ¼ 0.03, Z2¼ 0.55) and hip rotation/knee abduction-adduction (P ¼ 0.01, Z2 ¼ 0.61). These differences may be associated with female increased risk of ACL injury (Pollard et al., 2005). Female athletes’ movement patterns may not be variable enough to adapt to environmental constraints during basketball play resulting in ACL injuries. Males displayed the most flexible movements in all couplings. Interestingly, the ACLr group demonstrated variability that was greater than females but less than males in the majority of couplings. This study warrants further investigation into the effects of gender and ACL reconstruction on lower extremity joint coordination variability, and its implications to female injury.Annual Conference of the British Association of Sport and Exercise Sciences 2007