Older athletes: strength solutions for injury rehab

As athletes age, particularly into their senior years, they face two key challenges when striving to maintain performance. Firstly, there’s a need to minimize age-related declines in muscle power. Secondly, it’s increasingly important to avoid injuries that tend to accumulate over the course of a career. These two issues can be related as an injury disrupts the training process, preventing the training necessary to prevent losses in muscle power.

Minimizing injury impacts

Since decreases in muscle power and injury are both challenges likely to be faced by an aging athlete, it’s important to have a strategy to manage this reality. While a ‘don’t get injured in the first place’ is a great approach, injuries can still happen despite the best of intentions. And when they do, having options for minimizing their impact can make all the difference. It’s easy to assume that if an athlete injures their arm or leg and is unable to train it for some period of time, there’s nothing that can be done.

Fortunately, that’s not true. This is due to a phenomenon known as the ‘contralateral effect’, an effect we’ve explored before in previous articles. Training one arm can prevent strength and muscle losses in the other arms, even when that arm is completely immobilized (see here). Meanwhile, training one arm can make the untrained arm more resilient to muscle damage when exposed to future exercise loading (see here). What’s not as clear is whether the contralateral effect can lead to improvements in muscle power in older populations. And as resistance training can be performed using either high loads or low loads, it’s also not clear which type of training is more likely to create the best contralateral effect. Fortunately, the study we’re going to look at here has sought to answer these exact questions.

New research

A group of European researchers recruited 45 subjects to participate in a recent study designed to assess the contralateral effects of power training in older subjects⁽¹⁾. The subjects were all at least 65 years of age and had not been resistance training in the last three years, but were otherwise healthy and showing no signs of frailty or impaired physical function.

The study was set up as a within-person randomized control study. In other words, each subject served as their own control and was randomized into the specific intervention they performed. For all subjects, the study began with an 8-week control period, in which no training was performed. The subjects were tested before and after this control period to determine if any changes took place (ie baseline strength changes unrelated to training). Following the control period, the subjects were split into one of two groups:

·       A high-load power training group.

·       A low-load power training group.

The subjects trained twice per week on non-consecutive days using a horizontal leg press device. The training was performing unilaterally (ie on one side only) to allow for assessment of contralateral effects on the non-training leg.

The training

In the high-load training group, the subjects performed 6 x sets of six repetitions with a load that was 80% of their maximum 1-rep load. In the low-load training group, the subjects performed 6 x sets of twelve repetitions using a load that was 40% of their 1-rep maximum. By using half the resistance and twice the number of repetitions in the low-load group, the total volume was identical between the groups. This controlled for the amount of work that was done, allowing the researchers to compare the effect of loading intensity rather than the effect of volume. The subjects’ maximal strength was retested every four weeks to ensure the appropriate load was being used throughout the study.

For the repetitions themselves, the subjects were asked to lift the load as fast as possible, regardless of how fast the load actually moved. However, the eccentric phase of each repetition was to be performed in a controlled manner. For the high-load group, the subjects were asked to lower the load over the course of two seconds. In the low load-group, the subjects were asked to lower the load over the course of three seconds. The difference in eccentric duration accounted for the difference in challenge when lower different loads.

Testing

To evaluate the impact of the training interventions, the subjects underwent a series of tests before the control period, after the control period, and after the training period. First the subjects performed an isometric knee extension where they were tested for the maximal force they could generate, as well as how quickly they could generate force during.

The subjects also performed force-velocity testing on the same leg press device that they used during training. They performed a series of repetitions where the load progressed up to their maximum. For each repetition, the subjects tried to lift the weight as fast as possible. The load they lifted and the speed at which they lifted it were recorded. These measurements were then used to calculate several different metrics of power, included the theoretical maximal limb speed, force production, and power production.

Potential changes in muscle mass were measured using ultrasound technology, specifically examining mid-thigh cross sectional area. The larger the area, the bigger the muscle. To determine whether any improvements in strength, speed, or size were related to functional outcomes, the subjects performed three separate tests: a times 5-repetition sit-to-stand, a 3-meter timed stand up and go test, and a 30-meter maximal walking speed test. These tests all represented specific applications of power relevant to everyday life.

For all testing, the subjects used both their trained and untrained leg. The researchers didn’t just want to know if the training improved the trained leg. That wouldn’t be particularly interesting because of course it would! What they really wanted to know is whether that training led to improvements in the non-trained leg. If that’s the case, it would have important ramifications for those who can’t train a limb for an extended period of time.