Unilateral Eccentric Training: Preventing Weakness in Targeted Muscles

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Loss of muscle strength can be a harmful result when someone is unable to move a part of their body for a long period of time. But a new study may have found a way to protect against this, and it doesn’t even involve the affected body part at all.

Loss of muscle strength can be one of the most damaging results when someone is unable to move a part of their body for a long period of time.

But a new study from Edith Cowan University (ECU) may have found a way to compensate or even protect against this, and it doesn’t even involve the affected body part at all.

An injury or illness can cause a part of the body to become incapacitated for weeks or even months, causing unused muscles to weaken and lose their mass and strength, which can have a major impact on people’s lives.

Lead researcher Professor Ken Nosaka said it was already known that gaining muscle strength in one limb due to resistance training will transfer to the same muscle on the opposite side of the body.

“This is known as the cross-training effect,” he said.

 “However, the key aspect of this study is a particular type of muscle contraction that turned out to be the most effective,” Professor Nosaka said.

The study

The research was a collaboration between ECU and Professor Trevor Chen of National Taiwan Normal University. In the study, the non-dominant arm of 36 sedentary young people was immobilized using a cast on the elbow joint for three weeks .

They were then divided into three equal groups: a concentric contraction group that lifted a dumbbell using the non-immobilized arm, an eccentric contraction group that lowered a dumbbell, and a control group that did no exercises (see definitions below). While their arm was immobilized, the concentric and eccentric groups performed six weight lifting sessions twice a week, for three weeks. These sessions would see them perform five sets of six dumbbell curls with a dumbbell corresponding to 20, 40, 40, 60, 60 and 80 percent of their maximum strength over the six sessions.

The eccentric is the best

When the cast was removed, the no-exercise control group saw a more than 15 percent decrease in the strength of the immobilized arm. However, those who lifted weights saw little to no decrease in muscle strength of the immobilized arm.

The concentric group saw muscle strength reduced to 4 percent, but interestingly, muscle strength increased by 4 percent for the eccentric group, showing a stronger cross-education effect.

The researchers also measured the muscle size of the immobilized arm. The control group saw a decrease in muscle size of about 12 percent, while both concentric and eccentric muscle contractions with the opposite arm counteracted muscle atrophy in the immobilized arm. Muscle size still decreased by 4 percent for the concentric group, while, surprisingly, no decreases in muscle size were observed for the eccentric group.

Protective effect against muscle damage

All participants were asked to perform 30 eccentric contractions with their arm immobilized once the cast was removed, and the researchers measured several markers of muscle damage before, immediately after, and five days after the exercise. The control group showed very severe muscle soreness and loss of strength after exercise, and the concentric group showed much less damage.

Once again, the eccentric group saw the best results, providing a protective effect strong enough to reduce peak muscle soreness by 80 percent compared to the control group and by 40 percent of the concentric group .

Professor Nosaka said these results supported previous ECU research highlighting the benefits of eccentric exercise. “We already know that eccentric muscle contractions appear to be the most effective in promoting muscle strength and size gains, even at very small doses,” he said.

“It is important to investigate whether the results of this latest study are replicated for other muscles and whether eccentric resistance training is effective when it comes to immobilization in real injuries, such as ligament sprains or tears, bone fractures, 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.”

“Effects of unilateral eccentric versus concentric training of the non-immobilized arm during immobilization” was published in Medicine and Science in Sports and Exercise .