Injury sometimes causes a body part to be disabled, causing unused muscles to weaken and lose their mass and strength, which can have a huge impact on people’s lives. A new study may have found a way to offset or even protect against this — and it doesn’t even involve the affected body part at all.
Unrelated to the damaged body part, a recent Edith Cowan University (ECU) study may have discovered a strategy to mitigate or prevent this.
Resistance training will cause the identical muscle on the opposite side of the body to build strength in the same way that it did in the one limb. This is known as the cross-education effect.
One specific form of muscle contraction that was found to be the most efficient is the study’s major finding.
36 sedentary young men were placed in ET, CT, or the control group. Their non-dominant arms were immobilized for three weeks. During the immobilization period, ET and CT groups performed 5 sets of 6 dumbbell curl eccentric-only and concentric-only contractions, respectively, at 20-80% of maximal voluntary isometric contraction (MVCiso) strength over six sessions.
MVCiso torque, root-mean-square (RMS) of electromyographic activity during MVCiso, and bicep brachii muscle cross-sectional area (CSA) were measured before and after immobilization for both arms.
The strength of the arm that the cast had immobilized decreased by more than 15% in the control group after the cast was removed. However, the immobilized arm’s muscle strength showed little to no decline in those who lifted weights.
The CT saw muscle strength reduced to 4 percent, but interestingly, muscle strength increased by 4 percent for the ET group, showing a stronger cross-education effect.
Scientists also measured the size of the muscle in the arm that was immobilized.
While concentric and eccentric muscle contractions with the opposite arm prevented muscular atrophy in the immobilized arm, the control group experienced a 12% reduction in muscle size.
Amazingly, no losses in muscle size were seen for the ET group, while the CT group’s muscle size shrank by 4%.
Following removing the cast, each participant engaged in 30 eccentric contractions of the elbow flexors (30EC) using the immobilized arm. Several indicators of indirect muscle injury were measured before, immediately after, and for five days after 30EC.
The control group showed severe muscle soreness and strength loss after the exercise, while the concentric group showed far less damage.
Again, the eccentric group saw the best results, providing a protective effect strong enough for peak muscle soreness to be reduced by 80 percent compared to the control group and 40 percent of the concentric group.
Lead researcher Professor Ken Nosaka noted, “These results supported previous ECU research highlighting the benefits of eccentric exercise.”
“We already know eccentric muscle contractions appear to be the most effective at promoting muscle strength and size gains — even in very small doses.”
“It is important to investigate whether this latest study’s results are replicated for other muscles and whether eccentric resistance training is effective when dealing with immobilization in real injuries, such as ligament sprains or tears, bone fracture, and post-surgery. However, healthcare providers can recommend resistance training — and eccentric contractions in particular — to minimize the negative effects of immobilization and hopefully lessen its impact on people’s lives.”
Journal Reference:
- Chen, Trevor C et al. Effects of Unilateral Eccentric versus Concentric Training of Non-Immobilized Arm During Immobilization. Medicine & Science in Sports & Exercise. DOI: 10.1249/MSS.0000000000003140