Changes in biceps brachii muscle hardness assessed by a push-in meter and strain elastography after eccentric versus concentric contractions.
Level 3 - non-randomized controlled study
Non-randomized within-subject controlled study with fixed arm allocation.
PubMed 35655084 · doi:10.1038/s41598-022-13184-3
What was done
Ten men performed 5 sets of 10 eccentric contractions (ECC) with their non-dominant arms and 5 sets of 10 concentric contractions (CON) with their dominant arms using a dumbbell at 50% maximal voluntary isometric contraction (MVIC) force. Maximal voluntary contraction force, elbow joint angles, upper-arm circumference, muscle soreness, and biceps brachii muscle hardness (measured at maximally extended elbow joint via push-in meter [PM] and strain elastography [SE]) were assessed before and 1 to 4 days post-exercise.
What was found
All muscle damage markers showed greater changes after ECC than CON (p < 0.001). Muscle hardness assessed by PM and SE increased (p < 0.05) and peaked at 4 days post-ECC with 154.4 ± 90.0% (PM) and 156.2 ± 64.2% (SE) increases from baseline, but did not change significantly after CON. Post-ECC muscle hardness changes correlated between PM and SE (r = 0.752, p < 0.001). Changes in resting elbow joint angle also correlated with muscle hardness changes measured by PM (r = -0.772, p < 0.001) and SE (r = -0.745, p < 0.001).
Why it matters
The findings show that eccentric contractions induce marked, delayed increases in muscle hardness associated with muscle damage, and confirm that a portable push-in meter provides measurements comparable to ultrasound strain elastography.
Limits
The study had a very small sample size (n = 10) consisting solely of men. Exercise modes were not randomized across limbs (ECC was always performed by the non-dominant arm and CON by the dominant arm), and follow-up was limited to 4 days post-exercise.
Cited by
- supports Eccentric resistance exercise causes more tissue damage and muscle soreness than concentric exercise, requiring longer recovery periods.