Interindividual Differences in Trainability and Moderators of Cardiorespiratory Fitness, Waist Circumference, and Body Mass Responses: A Large-Scale Individual Participant Data Meta-analysis

Abstract

Although many studies have assumed variability reflects variance caused by exercise training, few studies have examined whether interindividual differences in trainability are present following exercise training. The present individual participant data (IPD) meta-analysis sought to: 1) investigate the presence of interindividual differences in trainability for cardiorespiratory fitness (CRF), waist circumference, and body mass; and 2) examine the influence of exercise training and potential moderators on the probability that an individual will experience clinically important differences. The IPD meta-analysis combined data from 1,879 participants from eight previously-published randomized controlled trials. We implemented a Bayesian framework to:1) test the hypothesis of interindividual differences in trainability by comparing variability in change scores between exercise and control using Bayes factors; and 2) compare posterior predictions of control and exercise across a range of moderators (baseline BMI and exercise duration, intensity, amount, mode and adherence) to estimate the proportions of participants expected to exceed minimum clinically important differences (MCIDs) for all three outcomes. Bayes factors demonstrated a lack of evidence supporting a high degree of variance attributable to interindividual differences in trainability across all three outcomes. These findings indicate that interindividual variability in observed changes are likely due to measurement error and external behavioural factors, not interindividual differences in trainability. Additionally, we found that a larger proportion of exercise participants were expected to exceed MCIDs compared with controls for all three outcomes. Moderator analyses identified that larger proportions were associated with a range of factors consistent with standard exercise theory and were driven by mean changes. Practitioners should prescribe exercise interventions known to elicit large mean Exercise individual response: IPD meta-analysis 3 changes to increase the probability that individuals will experience beneficial changes in CRF, waist circumference, and body mass. Running Title -Exercise individual response: IPD meta-analysis Key Points-For the purposes of this meta-analysis, we define "trainability" as the change in a given variable directly attributable to an effect of exercise training free of measurement error and confounding factors.-Larger exercise doses and other prescription factors consistent with standard exercise theory and larger mean changes were associated with larger proportions of individuals experiencing clinically meaningful changes in cardiorespiratory fitness, waist circumference, and body mass.-Regardless of whether individuals respond differently as a result of exercise training per se, clinicians should prescribe exercise doses known to elicit large mean changes in order to increase the probability that individuals experience clinically meaningful improvements in cardiorespiratory fitness, waist circumference, and body mass.

Heterogeneous Treatment Effects after Inspiratory Muscle Training during Recovery from Postacute COVID-19 Syndrome

“…This is the first investigation of heterogeneity in the effectiveness of an unsupervised home-based exercise or physical activity intervention using appropriate statistical methods. Although several recent studies have been unable to detect heterogeneous treatment effects for body composition, cardiorespiratory fitness, and blood pressure after supervised exercise training in adults (25–28), we found extremely strong evidence of individual responses for changes in inspiratory muscle strength after unsupervised IMT. This discrepancy is likely explained, at least in part, by the additional variability in intervention adherence and fidelity present in our study given its remote and unsupervised delivery method.…”

Variability in exercise tolerance and physiological responses to exercise prescribed relative to physiological thresholds and to maximum oxygen uptake

“…Many factors may contribute to $${\dot V_{{{\rm{O}}_{\rm{2}}}{\rm{max}}}}$$ response variability. Some relate to unmodifiable factors, such as age and genetics, and some to modifiable factors, such as training characteristics, whilst others relate to measurement error and biological variability (Bonafiglia et al., 2022; Meyler et al., 2021). A modifiable factor of interest is how exercise intensity is prescribed, which, when manipulated, may reduce response variability by creating a more homogeneous exercise and training stimulus among individuals (Meyler et al., 2021).…”

Inter‐individual variability in redox and performance responses after antioxidant supplementation: A randomized double blind crossover study

“…Regarding the effect of vitamin C supplementation on VO 2max , a remarkable mean increase of approximately 7 mL/kg/min was observed, with some individuals even experiencing an increase of almost 15 mL/kg/min. Such magnitudes of improvement are uncommon even in long‐term exercise trials 25 . However, it is important to note that our participants had vitamin C deficiency and compromised baseline VO 2max levels compared to their normal vitamin C levels counterparts (Figure 1).…”

“…Such magnitudes of improvement are uncommon even in long-term exercise trials. 25 However, it is important to note that our participants had vitamin C deficiency and compromised baseline VO 2max levels compared to their normal vitamin C levels counterparts (Figure 1). Thus, the supplementation protocol actually reversed the impairment in performance and should not be directly compared to the typical increases seen in individuals without nutritional deficiency and impaired baseline performance.…”

“…). Based on these concerns, more suitable methodological frameworks and statistical analyses have been proposed 15,22–24 and applied in some very recent original studies and meta‐analyses 25–30 . It is noteworthy that most of these studies do not support the idea of significant inter‐individual variability in response to an intervention, as evidenced by the larger variation observed in the responses of the control group compared to the intervention group.…”