Studies of Twin Responses to Understand Exercise Therapy (STRUETH): Body Composition

Abstract

Purpose We studied individual variability in exercise responses in twins. We hypothesized that 1) endurance (END) training would reduce fat mass whereas resistance (RES) training would increase lean mass, 2) individuals who did not respond to one modality would respond to the other, and 3) cross-sectional heritability estimates would be higher than estimates based on training responses. Methods DXA was undertaken in 84 same-sex untrained twins (30 monozygotic [MZ], 12 dizygotic [DZ]). Participants underwent 3 months of END and RES training, separated by 3 months washout. Twins trained in pairs. Results RES (P < 0.001) and END (P = 0.002) increased lean mass, with a greater change in RES (P < 0.001). Similarly, RES (P = 0.04) and END (P = 0.006) decreased fat mass. Eighty-four percent of subjects responded positively to RES for lean mass and 58% to END (P < 0.001). For fat mass, RES and END induced 56% and 66% responder rates, respectively (P = 0.28). Cross-sectional intraclass correlations, used to assess the similarity in twin responses, were higher for MZ than DZ pairs for all variables. Following training, only MZ pairs were significantly correlated (P < 0.001) for change in lean mass to RES. Conclusion To our knowledge, this study is the first to report individual responsiveness in body composition to both RES and END in the same subjects. Although RES and END induced favorable changes in fat mass, RES was superior for lean mass. The frequency of lean mass responders to RES exceeded that for END, whereas response rates for fat mass were similar. Cross-sectional heritability estimates were higher than training response estimates, and shared environment had the largest influence on changes in body composition. This study suggests that exercise professionals should consider modality and environmental factors when optimizing exercise interventions.

Resistance, but not endurance exercise training, induces changes in cerebrovascular function in healthy young subjects

“…Participants then crossed over to complete 3 mo of their second, alternate, exercise intervention (RES or END). Fat and lean mass were assessed using dual energy X-ray absorptiometry (22), fitness using a graded exercise V _ O 2max test performed on a treadmill and consisting of 3-min stages interspersed with 1-min rest periods. The test commenced at 8 km•h À1 and increased by 1 km•h À1 per stage until volitional exhaustion and maintained a 1% incline gradient.…”

“…END and RES exercise induce different physiological adaptations (22,23), including distinct peripheral vascular changes (24)(25)(26), possibly due to the different hemodynamic responses associated with each modality (19). For example, END results in sustained elevation in cardiac output and blood pressure, whereas RES induces oscillation in these measures (27).…”

A Systematic Review Examining the Approaches Used to Estimate Interindividual Differences in Trainability and Classify Individual Responses to Exercise Training

“…( Simoneau et al, 1986 ; Wilson et al, 1996 ; Timmons et al, 2005 ; Wadell et al, 2005 ; Sisson et al, 2009 ; Vollaard et al, 2009 ; Scharhag-Rosenberger et al, 2012 ; Schmid et al, 2013 ; Thomaes et al, 2013 ; Vincent et al, 2014 ; Sawyer et al, 2015 ; Stephens et al, 2015 , 2018 ; Wolpern et al, 2015 ; Stec et al, 2016 , 2017 ; Yalamanchi et al, 2016 ; Yoo et al, 2016 ; Schubert et al, 2017 ; Steele et al, 2017 ; Stuart et al, 2017 ; Williamson et al, 2017 , 2018 ; Yan et al, 2017 ; Valenzuela et al, 2018 , 2020 ; Weatherwax et al, 2018a , b , 2019 ; Wormgoor et al, 2018 ; Sandroff et al, 2019 ; Saric et al, 2019 ; Seward et al, 2019 ; Taaffe et al, 2019 ; Williams et al, 2019 ; Witvrouwen et al, 2019 ; Schulhauser et al, 2020 ; Thomas et al, 2020 ; Vellers et al, 2020 ; Walsh et al, 2020 ; Wang et al, 2020 ; Yu et al, 2020 ).…”

“…In 2015, biostatisticians raised concerns with these approaches and have advocated for more rigorous statistical approaches when estimating interindividual variability and classifying individual responses ( Atkinson and Batterham, 2015 ; Hecksteden et al, 2015 ; Hopkins, 2015 ). Despite many subsequent reviews echoing these concerns (reviews listed in Supplementary Table S1 ), we are aware of several studies published in the past year that did not adopt these statistical approaches ( Marsh et al, 2020 ; Thomas et al, 2020 ; Vellers et al, 2020 ; Wang et al, 2020 ). Because no study has systematically reviewed the approaches used to examine individual responses, it is unclear whether these recent studies are representative of the exercise training literature.…”

“…In support of these recommendations, we ( Schulhauser et al, 2020 ) and others ( Hecksteden et al, 2018 ) found that thresholds not considering error and/or a SWC or MCID inflate “response rates” compared with more conservative thresholds that consider both error and a SWC or MCID. However, recent studies have classified “responders” and “non-responders” using non-conservative thresholds ( Marsh et al, 2020 ; Thomas et al, 2020 ). Whether this observation is representative of the classification approaches used in the exercise training literature is unknown.…”