Abstract
Few have utilised a randomised controlled study design to monitor cardiovascular health in adults who replace automotive forms of transport with cycling1,2. Previous commuter cycling (CC) interventions observed enhanced cardiorespiratory fitness, mixed effects on body composition, whereas markers of insulin resistance have not been investigated. Furthermore, studies to date have omitted measures of physical activity (PA) and energy expenditure (EE) prior to initiating a routine of CC and therefore the contribution of the novel commuter cycling on existing PA and EE is unknown. The purpose of this study was to examine effects of CC on existing PA and EE, body composition and parameters of cardiovascular and metabolic health. Methods: Males and females who commuted by motorised transport were recruited and completed a graded exercise test on a cycle ergometer to determine V̇O2max, completed weighed food records, PA log books, and a validated PA questionnaire. Group assignment was randomised and matched for sex and fitness. The cycling group (CYC) (n=14, age 39±7 yr, body mass 77±11 kg, V̇O2max 2.8±0.8 l•min-1) were given bicycles and asked to cycle commute for 100+ min/wk for 10 weeks. The control group (CON) (n=14, age 34±8 yr, body mass 70±7 kg, VO2max 2.6±0.7 l•min-1) continued using motorised transport. Baseline (wk0) testing included cholesterol fractions, triglycerides, C-reactive protein, fasting insulin and glucose (HOMA-IR) and body composition (mass, skin folds), blood pressure, resting heart rate and measures were repeated wk10. CYC also underwent pre and post-intervention dual-energy x-ray absorptiometry (DXA) scans for assessment of body composition. Energy expenditure was estimated with energy intake data (wk0, wk4, wk8) with adjustment for energy balance from measures of fasted body mass at the same time points. Data were analysed using ANOVA for the group change from wk0 to wk10, and repeated measures ANOVA for data collected at 3 or more time points. Results: Analyses included 13 participants per group. CYC cycled 152 ± 60 min/wk, but did not alter (P>0.05) total levels of PA, energy intake or estimated EE. Consequently, no changes in body fat (P=0.69) or mass (P=0.61) were observed. V̇O2max (CYC: 10±17%, CON: -1.5±11%, P=0.03) and resting HR (CYC: -5±6%, CON: 3±9%, P=0.03) were improved, whereas diastolic BP increased in CON (CYC: -1±7%, CON 12±16%, P=0.02). There were no significant changes within or between groups for blood parameters. Conclusion: Commuter cycling for ~150 min/wk does not increase total PA and EE, which may be due to a reduction in non-cycling physical activities or the instruments used for PA and EE measures may have lacked resolution to capture change to short-lasting and spontaneous PA. Nevertheless, major markers for cardiovascular health were enhanced in just 10 weeks and the seasonal increase in diastolic BP observed in CON was prevented with CC in CYC. The lack of significant changes in blood parameters may be due to inadequate volume of exercise or duration of intervention. Research was supported by the New Zealand Heart Foundation and School of Physical Education, Sport and Exercise Sciences at University of Otago.