Exercise as it relates to Disease/Does high-intensity exercise reduce the risk of cardiovascular disease?

This is a critique of the article: The effects of a novel high intensity exercise intervention on established markers of cardiovascular disease and health in Scottish adolescent youth

Duncan S. Buchan University of the West of Scotland, United Kingdom. John D. Young Alan D. Simpson University of the West of Scotland, United Kingdom. Non E. Thomas Swansea University, United Kingdom. Stephen-Mark Cooper Cardiff School of Sport, United Kingdom. Julien S. Baker University of the West of Scotland, United Kingdom.

What is the background to this research?
It is well established that obesity is a major risk factor for cardiovascular and metabolic diseases. Moreover, poor aerobic fitness, poor diet, physical inactivity and hypertension contribute significantly to the development of cardiovascular disease (CVD) However, it is also established that engagement in a physically active lifestyle is key in the prevention of cardiovascular and various metabolic diseases, and while children and adolescents generally have little risk of CVD, issues may ensue in later life if an unhealthy lifestyle develops. It is known that regular physical activity protects against CVD risk; however, recent estimates suggest that current activity levels in youth in Scotland, which involve only 45 mins for a physical education (PE) class and may also be irregular, are not sufficient to prevent CVD risk in the future. Moreover, evidence suggests that youth spend less than 50% of PE time in moderate intensity activity. Therefore, there is a need to consider the non-traditional exercise interventions as a method of improving the health and well-being of Scottish youth. In adults, studies have shown positive effects high intensity exercise (HIT) and aerobic interval training interventions, which lead to improved health and well-being. In one study such interventions were found to be superior to a multidisciplinary approach that involved exercise, nutritional and psychological advice with greater improvements in cardiorespiratory fitness, endothelial function, measures of adiposity and blood pressure, and in measures of fasting glucose and high-density lipoprotein cholesterol than those involved in the multidisciplinary approach. Children and adolescents in the school setting have less time for such interventions and it is unclear whether HIT of a short duration would still be effective on the immediate and long-term health and well-being of youth. The aim of this study was simply to determine if HIT interventions improved CVD outcomes by measuring cardiorespiratory performance, muscular power and speed/agility. A second aim was to investigate the effects of the intervention on traditional markers of CVD i.e. blood pressure, percentage body fat and body mass index (BMI).

Where is the research from?
The research is published as a brief report in the Journal of Public Health Research (2012, 1:e24), which is an open access peer reviewed journal, and was conducted by researchers from Scotland and Wales - from the University of West Scotland, Swansea University, UWIC Wales. The senior author, Duncan Buchan, has over 70 publications and is a senior lecturer in exercise science and Julien S Baker is a professor (physiology) with several fellowships and now currently a professor in Hong Kong. The research team can be considered as experienced, widely published and reliable.

What kind of research was this?
This research is an interventional study, which is a prospective study specifically tailored to evaluate direct impacts of the preventative measures (interventions) on each parameter

What did the research involve?
After obtaining appropriate ethics approval, forty-one subjects aged 15-17 years, 35 boys and 6 girls, participated in the study and were randomly assigned to a non-exercising control group or to a HIT group. Anthropometric measures, blood pressure, cardiorespiratory fitness, muscular power, jumping height, running speed 10 metres, and agility were all measured pre-and post- intervention following standardised warm-up procedures.11 Post-intervention testing was within five days of the exercise session and all participants completed a validated physical activity questionnaire, which required them to detail their physical activity over the previous seven days.

13 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 equating to 1 repetition. This increased weekly by 1 repetition for six weeks and on the 7th week repetitions were interspersed by just 20 s recovery. This was performed 3 times weekly at the start of every PE class. The control group (20 boys, 4 girls) maintained normal activity.

Means and standard deviations were calculated for each observation point and The Anderson-Darling test was applied to confirm normality, and homogeneity of variance was assessed using Levene’s test. The results were analysed using a two way repeated measure analysis of variance. Where a Group × Time interaction was significant (P<0.05) the simple effects of Time were investigated for both the Control and HIT groups.

What were the basic results?
The intervention measures revealed that there were significant improvements in the HIT group for aerobic fitness, counter movement jump (CMJ) and agility performance compared to the control group. This is shown in the table below from the paper itself. Participants in the control group also experienced a significant decrease in CMJ performance post-intervention. There was no significant difference in activity levels within or between groups either pre- or post- intervention. Moreover, no significant difference was found for other parameters including stature, body mass, BMI, WHR, body fat, blood pressure and mean heart rate.

What conclusions can we take from this research?
This study supports the claim that brief intense exercise interventions may be useful for improving some components of physical fitness; i.e. cardiorespiratory fitness and agility. Also, that these improvements can be gained in a short time (3 sessions per week for 7 weeks).

However, there are a number of limitations to this study:
 * The sample size of only 41 with very few females makes it impossible to determine if girls in this age group might need different interventions.
 * The sample size is not large enough to give statistical power to form any firm conclusions about parameters that did not show any significant difference (i.e. body mass, BMI, WHR, body fat, blood pressure and mean heart rate).
 * The study was done in a narrow age band (15-17 years) and the results cannot be extrapolated to other younger age groups (there are differences in physical development).
 * The study was done in only one school and the study would benefit from data which included students from other schools.
 * Genetic, socioeconomic and general health status has not been taken into account.
 * The study did not follow subjects’ long term to determine if the interventions made during adolescence had any improvements on subjects over time; and finally,
 * These findings may not be applicable to other country settings.

Practical advice
This study has shown that brief intense exercise interventions may be useful for improving cardiorespiratory fitness and agility, which may also have long term benefits; so, it is important to encourage young people to exercise regularly.

There are many reasons to encourage children and adolescents to exercise: Regular exercise can also help people sleep more deeply.
 * Psychologically it can help those who have mild depression and low self-esteem as endorphins are elevated.
 * Physically, exercise helps people to control their weight and lower the risk of some diseases such as CVD, high blood pressure and metabolic diseases including type 2 diabetes.
 * Finally, regular exercise, especially when young, can protect against osteoporosis; simple weight-bearing exercises like jumping, running, or brisk walking assists with bone health during the ageing process.

Further information

 * https://www.who.int/news-room/fact-sheets/detail/physical-activity
 * https://www.health.gov.au/health-topics/physical-activity-and-exercise/about-physical-activity-and-exercise
 * https://bmcmedicine.biomedcentral.com/articles/10.1186/1741-7015-11-172
 * https://www.heartfoundation.org.au/heart-health-education/physical-activity-and-exercise
 * https://www.nature.com/articles/s41390-020-01194-8
 * https://www.sciencedaily.com/releases/2018/10/181015100459.htm
 * https://www.aihw.gov.au/reports/risk-factors/insufficient-physical-activity/contents/insufficient-physical-activity