Time Course of Changes in Muscle and Tendon Properties During Strength Training and Detraining

Abstract

The purpose of this study was to investigate the time course of changes in mechanical and morphological properties of muscle and tendon during isometric training and detraining. Eight subjects completed 3 months of isometric knee extension training and detraining for another 3 months. At beginning and on every 1 month of training and detraining periods, muscle strength, neural activation level, muscle and tendon cross-sectional areas (CSA), and tendon stiffness were measured. Training increased muscle strength and neural activation level by 29.6 and 7.3% after 2 months and by 40.5 and 8.9% after 3 months (all p's < 0.05). Muscle CSA and tendon stiffness did not change until 2 months of training period, and afterward, the increases in muscle CSA and tendon stiffness reached statistical significance at the end of training period (both p's < 0.05). During detraining period, muscle strength and neural activation level did not change, although muscle CSA and tendon stiffness decreased to pre-training level at 1 and 2 months of detraining, respectively. These results suggest that the adaptations of tendon properties and muscle morphology to resistance training are slower than those of muscle function and inversely that the adaptations of former to detraining are faster than those of latter.

Time course of changes in the human Achilles tendon properties and metabolism during training and detraining in vivo

“…At 1 month of detraining, maximal elongation of the tendons was greater than that post-training. This result agreed with our recent finding (Kubo et al 2010). In addition, tendon stiffness had already returned to the pretraining level at 1 month of detraining.…”

“…These results supported our recent finding (Kubo et al 2010). Furthermore, from a metabolic point of view, collagen synthesis (estimated from serum biochemical markers), content (estimated from echointensity), and structure (estimated from MRI signal intensity) in the human tendons changed at the 2-month point of the training period.…”

“…Furthermore, we reported that tendons adapted to resistance training slower, but to detraining faster, than muscle function (Kubo et al 2010). However, the mechanisms responsible for the changes in the mechanical properties of human tendons are unknown.…”

Comparison of muscle hypertrophy following 6-month of continuous and periodic strength training

“…Previous studies have reported no significant decrease in muscle strength after short-term (2-6 weeks) detraining (Hortobagyi et al 1993;Kraemer et al 2002). Recently, one study found no significant change in the neural activation level after 3 months of detraining because muscle CSA had decreased to its pretraining level (Kubo et al 2010). Therefore, the relatively short duration of detraining did not affect the increase in training-induced muscle strength.…”

Human achilles tendon plasticity in response to cyclic strain: effect of rate and duration

“…length and CSA) were determined by means of magnetic resonance imaging (MRI). Only the participants of the two experimental groups (intervention 1 and 2) were investigated, as changes of the AT morphological properties of the control group participants without a specific stimulus were not expected (Kubo et al, 2010;Kubo et al, 2006). A 0.25 T magnetic resonance scanner (G-Scan, Esaote, Italy) captured transversal and sagittal magnetic resonance scans of the AT [3D HYCE (GR) sequence, TR 10 ms, TE 5 ms, flip angle 80 deg, slice thickness 3 mm, one excitation] while the participants lay in supine position with the hip and knee extended and the ankle fixed in a relaxed position.…”