MET-min/week, as a parameter reflecting physical activity, showed a borderline significant effect on FF (P=0.034), but this effect was only observed for one muscle (ES) and only when considering the logarithmic value of this parameter.
Another study evaluating factors influencing lumbar spine muscle TMV concluded that height was a highly significant factor influencing PS, MF, and ES volume ( 33 ), which was also demonstrated in the present study.
Because of the marginal significance of this effect and the subjective nature of MET-min/week, we decided not to include this factor in the subsequent multivariable analysis.