Ankle movement and muscle displacement

A total of 56 healthy individuals (25♀, 31♂; 25.36 ± 3.9 years; BMI 23.0 ± 2.8) aged between 18 and 40 years were recruited. According to Faul et al.^{23 (link)}, an a priori biometric sample size calculation was performed, using the algorithm of G*Power, version 3.1.5 (Heinrich-Heine University of Düsseldorf, Germany) for each of the two hypotheses. The computation showed hypothesis one (dorsal extension of the ankle at extended knees causes a higher displacement of SM than ankle movement at flexed knees) to require n = 29 individuals (α = 0.05, 1 − β  =  0.8, Cohen’s d = 0.5, Dropout: 5%). Hypothesis two (SM displacement depends on ankle movement/GM displacement) yielded a minimum of n = 56 participants (α = 0.05, 1 − β  =  0.8, Cohen’s f² = 0.15, Dropout: 5%). Consequently, the enrollment of n = 56 individuals ensured sufficient power to detect both, significant differences (hypothesis 1) and associations (hypothesis 2) with medium effect sizes according to Cohen^{24 (link)}.
Flyer and poster advertising as well as personal addressing were used for recruitment. Exclusion criteria were defined as orthopedic, cardiovascular, neurological, endocrine and psychiatric diseases, acute inflammation, intake of drugs that modify pain perception and proprioception, presence of delayed onset muscle soreness, pregnancy or nursing period, and history of surgery in the lower limb.