Myofibrillar and collagen protein synthesis in human skeletal muscle in young men after maximal shortening and lengthening contractions.
Level 2 - randomized trial
Individual randomized within-subject controlled trial
PubMed 15572656 · doi:10.1152/ajpendo.00387.2004
What was done
Eight healthy young men (mean age 21.9 ± 0.6 years, BMI 24.9 ± 1.3 kg/m²) completed a unilateral exercise protocol comparing maximal lengthening contractions (LC; peak torque 299 ± 18 N·m) and work-matched maximal shortening contractions (SC; peak torque 225 ± 7 N·m) using the contralateral knee extensors. Each leg completed 6 sets of 10 contractions with equalized total work (10.9 ± 0.7 vs. 10.9 ± 0.8 kJ, P = 0.83). Participants consumed intermittent protein and carbohydrate feedings (0.1 g·kg⁻¹·h⁻¹ each) during an 8.5-hour recovery period, and skeletal muscle myofibrillar protein synthesis (MPS) and collagen protein synthesis (CPS) were measured.
What was found
Both exercise modalities elevated MPS above resting levels, but LC caused a significantly more rapid rise in MPS than SC (P < 0.01). In contrast, both contraction types produced identical significant elevations in CPS above rest (P < 0.001).
Why it matters
This study demonstrates that when mechanical work is equalized, eccentric muscle actions stimulate a faster early myofibrillar protein synthetic response than concentric actions, providing a physiological basis for eccentric resistance training.
Limits
The sample size was very small (n = 8) and limited to healthy young men. The abstract only reports acute synthetic responses over 8.5 hours rather than chronic muscle hypertrophy, and exact numerical rates for protein synthesis are not provided in the abstract.
Cited by
- contradicts The first physiological response after a training stimulus is the synthesis of collagen to reinforce fascial connective tissue containers prior to adding muscle.