26 Nov, 10 | by Karim Khan
Duncan S Buchan 1, Julien S Baker 1, Robert M Malina 2, Non E. Thomas 3
1. University of the West of Scotland
2. The University of Texas at Austin
3. Swansea University
We read with interest the recent statement released by BASEM on 26th November 2010 which criticises the way physical education (PE) is being taught in the United Kingdom. Previous authors suggest that youth spend less than 50% of PE time in moderate intensity activity and thus fail to procure health related benefits . Interestingly, a recent investigation demonstrated a positive role for brief, interval training as a means of improving the health status of obese and overweight adolescents with unfavourable cardiometabolic profiles . With this in mind we successfully developed and implemented a novel 7 week exercise intervention which aimed to determine the effects of PA programmes of different intensities and duration on three components of physical fitness, namely: cardiorespiratory fitness, muscular fitness and speed/agility . Full details of the protocol can be found elsewhere [4,5].
Briefly, a cohort of adolescent school youth (N = 47 boys and 10 girls, 16.4 ± 0.7 years of age) volunteered to participate in the study. Ethical approval was received from the University of the West of Scotland Ethics committee. Maturation status was obtained prior to experimental data collection. Participants were recruited from two PE classes in years 5 and 6. Year 5 pupils acted as the control group whereas year 6 pupils were randomly assigned to a high intensity training group (HIT) or a moderate (MOD) intensity group. Participants in the HIT group (15 boys, 2 girls) were required to complete a 30 s maximal effort sprint within a 20 m distance separated by cones. Participants were instructed to sprint from the midpoint to the first marker, turn, and then sprint 20 m in the opposite direction to the second marker. Participants repeated the protocol four times with a 30 s recovery period between sprints. This equated to 2 mins of maximal effort sprinting interspersed with 2 min recovery. The protocol was performed 3 times weekly. Training progression was implemented by increasing the number of repetitions from four during weeks 1 and 2, to five during weeks 3 and 4, to six during weeks 5 and 6. During week 7, participants still performed six repetitions but each was interspersed by only 20 s recovery.
Participants in the MOD group (12 boys and 4 girls) were instructed to exercise at a moderate intensity of 70% VO2max as utilized in other studies , by running steadily for a period of 20 mins. The speed of exercise was determined by each participant’s performance in the 20 metre multistage fitness test (MSFT). Participants were instructed to keep pace with a CD that emitted a continuous audio signal for a period of 20 min. All participants had indices of obesity and blood pressure recorded in addition to four physical performance measures pre and post intervention. These included the 20 MSFT, the counter movement jump (CMJ), agility and the 10m sprint test.
Overall, it was apparent that specific physiological adaptations occurred relative to the stimulus provided. Participants in the MOD group experienced a 26.8% improvement in 20 MSFT and a 7.3% improvement in CMJ performance. Participants in the HIT group experienced an 8.3% and a 5.1% improvement in both the 20 MSFT and CMJ. Participants in the HIT group also experienced a 1.5% and 5% improvement in 10-m sprint and 505-agility performance though no improvements were noted in the MOD group. Though the participants in both groups experienced improvements, it should be noted that these improvements in the HIT group occurred in 85% less exercise time compared to that of the MOD group. Participants in the HIT group also experienced a significant reduction in systolic blood pressure SBP post-intervention (112 ± 10 vs. 106 ± 11 mm Hg) (P=0.017). Thus, significant improvements in physical fitness were found in both groups after exercising for only seven weeks (3 times per week).
Despite overwhelming evidence supporting the health benefits of regular PA, many youth fail to meet minimal recommendations. This study has demonstrated that HIT is a time efficient means of improving components of health in youth. Given the time constraints of school curricula, incorporating a HIT protocol into the PE curriculum may function to improve PA levels and health status of adolescents. Further research investigating the effects of HIT on markers of health status in youth seems recommended.
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3. Ortega FB, Ruiz JR, Castillo MJ, Sjostrom M (2008) Physical fitness in childhood and adolescence: a powerful marker of health. Int J Obes 32: 1-11
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