Plain language summary
Registration to recreational runs is likely used by many participants as a motivational tool for regular endurance training in order to improve health-related physical fitness. The study aims to evaluate (1) the impact of body composition changes on the evolution of running speed (2) the effects of ageing on this aforementioned relationship and (3) the influence of baseline body composition on the evolution of running speed. The study is a longitudinal cohort study that included people >16 years who ran in a timed city run. The study population included 377 women and 509 men. Results indicate that running speed over 5km in women and 7km in men increased as fat mass index (is a measure of relative fat content), and, to a lesser extent, body mass index decreased. The impact of fat-free mass index (is an alternative to body mass index which accounts for a person's muscle mass) was gender-specific. The study highlights the importance of following body composition in ambitious recreational runners who want to maintain their performance as long as possible.
Abstract
A low fat mass is associated with a good running performance. This study explores whether modifications in body composition predicted changes in running speed. We included people who underwent several measurements of body composition by bioelectrical impedance analysis between 1999 and 2016, at the "Course de l'Escalade", taking place yearly in Geneva. Body composition was reported as a fat-free mass index (FFMI) and fat mass index (FMI). Running distances (men: 7.2 km; women: 4.8 km) and running times were used to calculate speed in km/h. We performed multivariate linear mixed regression models to determine whether modifications of body mass index, FFMI, FMI or the combination of FFMI and FMI predicted changes in running speed. The study population included 377 women (1419 observations) and 509 men (2161 observations). Changes in running speed were best predicted by the combination of FFMI and FMI. Running speed improved with a reduction of FMI in both sexes (women: ß -0.31; 95% CI -0.35 to -0.27, p < 0.001. men: ß -0.43; 95% CI -0.48 to -0.39, p < 0.001) and a reduction of FFMI in men (ß -0.20; 95% CI -0.26 to -0.15, p < 0.001). Adjusted for body composition, the decline in running performance occurred from 50 years onward, but appeared earlier with a body mass, FFMI or FMI above the median value at baseline. Changes of running speed are determined mostly by changes in FMI. The decline in running performance occurs from 50 years onward but appears earlier in people with a high body mass index, FFMI or FMI at baseline.
Methodological quality
Allocation concealment
:
Not applicable
