Effect of immobilization and retraining on torque-velocity relationship of human knee flexor and extensor muscles

Abstract

The effect of 2 weeks immobilization of the uninjured right knee and 10 weeks of retraining on muscle torque-velocity characteristics was investigated in nine young subjects. Left and right knee extension and flexion maximal voluntary isometric torque (Tmax) and dynamic torque at 60 degrees s(-1) (T60) and 180 degrees x s(-1) (T180) were measured before (PRE) and after immobilization (POST) and after 3 (R3) and 10 (R10) weeks of dynamic retraining. The torque-velocity relationship was quantified by expressing T60 and T180 relative to Tmax (NT60 and NT180, respectively). For the right extensor muscles, percutaneous biopsy samples were obtained from the vastus lateralis muscle and fibre type distribution was measured. POST extension and flexion torque (mean of Tmax, T60 and T180) decreased by 27% and 11%, respectively. During the course of the experiment, the changes in NT60 and NT180 were similar. POST extensor muscle NTV (mean of NT60 and NT180) was decreased significantly (12%, P<0.05), but no significant change was found for flexor muscle NTV (+ 3%). At R3 Tmax, dynamic torque and NTV were restored to normal. Unlike isometric torque, NTV did not change from R3 to R10. No changes in fibre type distribution were found. The adaptation of muscle length is suggested as the mechanism to explain the change in NTV.

Effects of aging on muscle mechanical function and muscle fiber morphology during short-term immobilization and subsequent retraining

“…This observation corresponds well with findings by Deschenes et al (14), albeit they reported slightly lower changes in maximal isometric and dynamic knee extensor strength in old and young healthy men after 7 days of lower limb immobilization using a knee brace. The 15.4% drop in maximal isometric muscle strength that was observed in YM is in agreement with previous reports in young healthy individuals after similar periods of muscle disuse (10 -14 days) (6,7,13,25). Interestingly, rapid force capacity (RFD, impulse) was affected at greater extent in OM (ϳ25-37% reduced) than in YM (ϳ13-16% reduced), especially during the initial phase of muscle contraction (0 -50 ms).…”

“…In agreement with previous studies using similar periods of muscle disuse and retraining in healthy young individuals, full recovery of maximal isometric and slow dynamic muscle strength was observed (16,17,19,25). Findings from animal studies suggest that the recovery in muscle mechanical function and size after disuse may be impaired at old age (42).…”

“…Similar to the long-term effects of aging, short-term muscle disuse has been found to also have a substantial detrimental influence on muscle mechanical function, and, depending on the model and duration of disuse, marked decreases in maximal leg strength (6,7,13,14,16,17,19,23,25,41) and rapid force capacity (6,13,23) have been reported. However, the far majority of these studies were carried out in young individuals (cf.…”

Immobilization effects in young and older adults

“…White and Davies (1984) reported a 24% reduction in muscle strength of the plantar flexors, while Hespel et al (2001) and Labarque et al (2002) reported that quadriceps muscle strength decreased 22% after 2 weeks of leg immobilization. Immobilization of the forearm muscles in healthy young women resulted in a 29.3% decrease in muscle strength after 9 days (Miles et al 1994).…”

Strength training the free limb attenuates strength loss during unilateral immobilization

“…or unloading (14,22,25,26,37). In general, cast or brace immobilization protocols appear to result in more pronounced strength loss (14,18,21,22,25,26,37) compared with other unloading or disuse protocols such as slinging or suspension (2,6,7,28,30).…”