Impact of resistance training on correlates of physical activity and physical activity levels in youth
In youth, there are several benefits of being physically active which are well established. Regular participation has the potential to improve a child’s emotional, social and cognitive well-being, as well as physical fitness. Additionally, one of the key identified consequences of not being sufficiently active is the increased chance of obesity, which has significant implications for health. While the UK physical activity (PA) guidelines recommend ‘activity to develop movement skills, muscular fitness and bone strength’, there has been limited research to date on the impact of resistance training (RT) on health-related outcomes in youth. RT has been suggested to have a positive impact on weight status, fundamental movement skills (FMS) and ‘the self’, with strength being identified as a possible mechanism underlying these effects. These outcomes are identified as being associated with PA (thus, correlates of PA). Therefore, they may be important mediators of a possible effect of RT on moderate to vigorous physical activity (MVPA). The overall purpose of this thesis was to therefore explore the impact of RT on strength, correlates of PA, and PA levels in youth. Three systematic reviews and meta-analyses provided a comprehensive literature review on the effect of RT on three identified correlates of PA: weight status, fundamental movement skills (FMS) and ‘the self’ in youth. These reviews have each been published in Sports Medicine - Open. Overall, there was evidence to suggest that RT could have a positive impact on the specified correlates of PA, supporting the hypothesis that there could be a positive effect of RT on PA levels. It was apparent that further research would be beneficial, particularly as there was not an extensive volume of quality research focused on the impact of isolated RT on the correlates of PA and directly on MVPA. Based on the information obtained through the systematic reviews, two feasibility studies were developed and undertaken that explored recruitment, location, participants, assessment, and intervention design with the aim of informing a pilot study. These studies informed the design of the pilot study which was a quasi-randomly controlled RT pilot intervention in 12, inactive and/or overweight/obese 8-10 year olds. Pre and post intervention assessments for strength, physical self-perceptions (PSPs), weight status, fundamental movement skills (FMS), and PA levels were completed. The exercise group (EG) participated in a 10-week RT programme twice a week. There were significant time x group interactions for FMS (CAMSA total P = 0.016, CAMSA skill score P = 0.036) and stretch stature (P = 0.002) with the EG displaying larger changes than the CG. Additionally, large effect sizes were evident for CAMSA total score (Hedges’ g = 0.830, P = 0.138), CAMSA skill score (Hedges’ g = 0.895, P = 0.112) and relative strength (Hedges’ g = 0.825, P = 0.140) although these did not reach conventional levels of statistical significance. This study provided evidence that there are some positive effects of RT on correlates of PA, although unfortunately, there were not sufficient MVPA data to enable any association between RT and PA levels to be investigated in detail. However, this trial enabled the calculation of sample sizes to inform the design of a future definitive RCT. It was evident from the attendance figures and comments from the feedback sessions that a RT intervention was feasible in an inactive and/or overweight/obese youth population, lending support for a larger scale study. Overall, the thesis provides evidence to support the hypothesis that RT could have a positive impact on strength and the correlates of PA, but it is still unclear whether there is an impact on MVPA. This body of research also demonstrates that RT is a feasible activity for the specified population. The findings of this thesis inform the development of future PA interventions to support children to increase and/or maintain PA participation that includes both strength-based activity and MVPA. This thesis builds on previous work that has explored the topic of RT and the health of youth and introduces the novel concept that there may be a beneficial effect of RT and PA levels.