Calf muscle strength in humans

In an effort to measure strength characteristics of the calf muscles, 18 su bjects (14 male, 4 female, age =34.3 +/-2.4yrs) were tested using a special ly designed torque velocity device (TVD). This TVD is a hardware interface with the subject's lower leg which stabilizes the leg for calf muscle stren gth measurements. Calf muscle strength measurements consisted of 1) isometr ic force production at ankle angles of 80, 90, and 100 degrees of plantar f lexion, 2) peak torque at six isokinetic angular velocities 0.52, 1.05, 2.0 9, 3.14, 4.19, and 5.24 rad x s(-1), and 3) a fatigue test consisting of 30 maximal contractions at 3.14 rad x s(-1). The greatest force production oc curred at 80 degrees of ankle plantar flexion (148.5 +/- 40.2 Nm). Isokinet ic force production ranged from 114.1 +/- 24.7Nm at 0.52rad x s(-1) to 16.8 +/- 6.5 Nm at 5.24 rad x s(-1). A fatigue test consisting of 30 maximal re petitions at 3.14 rad x s(-1) resulted in a 61 +/- 15% decline in force pro duction. To assess reproducibility and day to day variation, measurements a t 1.05 and 2.09 rad x s(-1) were made during five different trials in a sin gle day and one trial per day for three days, respectively. The within subj ect coefficient of variation was 2.6 to 6.5% for reproducibility and 1.9 to 7.4% for day to day variation. Magnetic resonance imaging (MRI) of the low er limb and muscle biopsy specimens from the gastrocnemius (lateral head) a nd soleus muscles were obtained to examine the relationship between strengt h and morphological characteristics of the calf muscles. Cross-sectional ar ea of the primary plantar flexors (gastrocnemius and soleus) was 47.9 +/- 1 .3 cm(2) while muscle volume was 642 +/- 16 cm(3). Muscle fiber composition of the gastrocnemius and soleus averaged 57 +/- 2 and 85 +/- 3% type 1 fib ers, respectively. A poor correlation was found between fiber type and maxi mal isometric force production (r=0.38; p>0.05). However, calf muscle stren gth and muscle size was positively correlated (r=0.76; p<0.05). These data indicate that using the TVD interface to stabilize the lower leg is a relia ble and reproducible procedure for the measurement of calf muscle strength.