Effects of seated isokinetic eccentric training and detraining on mobility, balance, strength, muscle size and architecture in older adults

Introduction: Substantial increases in lower-limb strength, muscle mass and mobility occur in older adults following eccentric resistance training, however the impact on static balance (postural sway) is unknown with limited data describing detraining effects following the cessation of training. As static balance may be influenced more by ankle than hip and knee musculature, the present study examined the impact of a 6-week isokinetic eccentric training programme targeting the hip, knee, and ankle extensor musculature and 8 weeks of detraining on neuromusculoskeletal characteristics in older adults.
Methods: Maximal eccentric lower-limb force, vastus lateralis (VL) thickness, pennation angle and fascicle length, static balance (postural sway), and mobility (Timed-Up-and-Go [TUG]) were measured in 15 participants (age = 69.5 ± 5.9 y, mass = 75.5 ± 15.3 kg, height = 1.6 ± 0.1 m) before and after the 6-week training programme using dynamometry, sonography, and force platform analyses. All measures were then re-examined 8 weeks later to quantify detraining effects. Training was performed twice-weekly on a recumbent stepper (BTE Eccentron) using an alternating unilateral isokinetic eccentric leg press motion for 5 min (week 1) or 10 min (weeks 2-6) at 50% MVC and 40 contractions per minute. An additional 5 min of straight-legged unilateral eccentric dorsiflexions were performed on each limb to target the ankle plantarflexors. Strength was reassessed every 2 weeks to ensure subjects’ training intensities remained at 50% MVC, with rate of perceived exertion (RPE) recorded after each training session.
Results: Significant (P < 0.05) increases in lower-limb eccentric strength (39.4 ± 25.0%), VL muscle thickness (9.9 ± 6.8%), pennation angle (5.0 ± 5.0%), fascicle length (4.8 ± 4.4%), and decrease in TUG time (7.7 ± 6.4%) were detected immediately after the 6-week training programme; no change in any postural sway metric occurred. RPE remained low-to-moderate throughout the programme (3.6 – 4.5 out of 10). Eight weeks later, strength (30.5 ± 28.7%), muscle thickness (7.1 ± 6.5%), pennation angle (4.9 ± 6.8%), and mobility (8.2 ± 6.1%) remained significantly greater than pre-training levels.
Conclusion: Substantial improvements in strength, muscle size and mobility were achieved whilst training with low RPE, however no improvement in static balance occurred. Nonetheless, limited regression eight weeks after the completion of the training programme is indicative of a prolonged functional benefit. As older adults are more prone to periods of inactivity, these findings have important practical implications for exercise prescription where clinicians aim to develop and preserve functional performance.