Differences in post-exercise T2 relaxation time changes between eccentric and concentric contractions of the elbow flexors.
Level 3 - non-randomized controlled study
Controlled within-subject contralateral arm study with fixed sequence
PubMed 27632383 · doi:10.1007/s00421-016-3462-3
What was done
Twelve young men performed five sets of six maximal isokinetic (30°/s) eccentric contractions (ECC) with one arm followed by concentric contractions (CON) with the contralateral arm. Magnetic resonance imaging measured transverse relaxation time (T2) and cross-sectional area (CSA) of the biceps brachii, brachialis, and brachioradialis. Maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), and muscle soreness were assessed before, immediately after, and 1, 3, and 5 days after exercise.
What was found
Immediately post-exercise, muscle T2 increased significantly more after CON (27–34%) than ECC (16–18%, p < 0.05), returning to baseline by day 1 post-CON. Following ECC, biceps brachii and brachialis T2 increased by 9–29% at 1–5 days post-exercise (p < 0.05). MVC torque and ROM decreased significantly more after ECC than CON (p < 0.05), and muscle soreness developed exclusively after ECC. Biceps brachii and brachialis CSA increased immediately after CON, whereas delayed increases in brachialis CSA occurred only after ECC (p < 0.05). Post-ECC T2 changes did not correlate with changes in MVC torque, soreness, or CSA, but immediate post-ECC T2 increases correlated with peak T2 at 1–5 days post-ECC (r = 0.63, p < 0.05).
Why it matters
Immediate post-exercise T2 increases reflect greater metabolic activity during concentric contractions, whereas delayed T2 elevations after eccentric exercise reflect distinct muscle damage processes that do not directly correlate with standard functional markers.
Limits
The sample was small (n = 12) and included only young men. The exercise sequence was fixed (ECC performed before CON) rather than randomized or counterbalanced. Follow-up ended at 5 days post-exercise, before complete recovery of all measured variables.
Cited by
- supports Eccentric resistance exercise causes more tissue damage and muscle soreness than concentric exercise, requiring longer recovery periods.