Evan Stevens
The first talk in this second session was about how balance training can be used to augment neural plasticity in older individuals. As we age, we lose muscle mass and balance ability. The loss of balance comes from a decrease in inhibitory control. We will have increased cortical excitability, which means we have a tougher time controlling involuntary actions.
The researchers’ hypothesized that by practicing balancing acts, the brain would be forced to reinforce and alter certain neural pathways. Changing the wiring, essentially. Their goal was to show whether improvements in balance will lead to improvements elsewhere. Be it performance, the rate and severity of falls, or otherwise.
However, when the researchers put their hypothesis to the test, they found that balance training did not change any neural parameters. Nor did it translate to improvements in other aspects of performance.
The researchers split their group of seniors (65 and over) in two. One group would perform balance training on a slack line, and the other would not. At baseline, the groups were matched and not significantly different. Over the course of the two week study, the slackline group would train and practice on the slack line for an hour a day, and the control group would only perform simple tilt-based balance exercises (they would bend over or bend to the side and have to catch themselves).
At the end of the study they retested both groups on the slackline and, as predicted, they found that the slackline group performed the balance task with fewer errors than did the control group that trained on solid ground using tilt-based training methods. However, when either group was asked to perform a different task- walking along a straight line, neither group was statistically different.
This led the researchers to conclude that the balance training only led to task-specific improvements rather than improvements that could be translated to other tasks. However, the researchers dug a little deeper and found that the trained individuals had significantly improved H-reflex scores than the untrained individuals. The H-reflex is a measure of the muscle’s ability to fire in response to stimulus, which can signify changes in the synapses of the spine.
Take Away
The researchers surmised that although the balance training seemed to improve the individual task performance (slackline) but did not lead the overall balance improvements, the H-reflex improvements could mean changes to neural plasticity could take a little more time than just two weeks of training.
Second Talk
The second talk of the session dealt with similar themes, namely how balance training could alter neural excitability pathways. This study took elderly individuals and asked them to perform a step-up on one leg. One group performed it using a hand rail to help balance and the second group performed the task without grasping a hand rail (unassisted). The unassisted group was better able to control the sway of their body by the end of the study; they displayed far fewer errors (errors recorded as having to grab the hand rail for assistance, or stepping on their other leg while doing single leg raises.
The researchers found that the calf muscles of the individuals who performed the tasks unassisted had significantly improved H-reflex responses and a better ability to adapt to changes in movement and sway. The researchers performed a number of neural scans after the tests in hopes of finding changes to the neural pathways in the brain (improved plasticity) but found nothing. While there were improvements in performance and postural stability, there were no changes in the brain. Similarly to the last talk, time may have been a limiting factor, as perhaps a longer intervention with more follow-ups would reveal statistically significant changes in brain function.
Take Away
Short term balance training seems to only improve task-specific performance. However, improvements in nerve excitation could mean that training improvements could take longer than two weeks of training. The implications could range from fall and injury prevention to improvements in sport performance.
Third Talk
The next talk dealt with sprinting mechanics in masters athletes. We know that performance tends to decrease in relation to age and is linear across all activities (performance declines at the same rate regardless of distance, sprints, throws, etc). This is, in part, due to the decrease in force generated in the lower limbs. But it is also due to the decrease in velocity and explosiveness that comes with increased age. Yet, sprint training in your 70s can lead to the same parameters of performance as untrained individuals in their 40s; we just do it differently because our mechanics have changed. As we age our step length and power decreases, but our stride frequency remains the same.
What this equates to is that we spend more time on the ground rather than “in flight,” which explains how our stride frequency changes. As well, the way in which we accelerate changes as we age. Younger people accelerate in a horizontal manner, driving force more parallel to the running surface. As we age our acceleration and force output turns more vertical; meaning running efficiency is far lower in older age than younger. The researchers performing this study found that masters athletes slow down because they are less efficient at orienting force output.
The researchers concluded that if we cannot limit loss of muscle strength, then we may be able to prevent the linear decline in performance by limiting the loss of technique as we age. Technique training and maintaining proper running form translates to better efficiency and better performance.
Take Away
We lose strength and the ability to orient force output as we age. To perform better as masters athletes, we should do more work on the maintenance of technique. We should also turn vertical force and acceleration output into more horizontal output.
Fourth Talk
The researchers who presented the fourth talk in this session discussed how movement specific reinvestment could alter stepping and visomotor control during walking. The researchers asked elderly subjects to work through an obstacle course that involved stepping up, around, or over certain obstacles. The goal was to figure out how conscious control affected performance.
During some of the tests participants were asked to focus intently on each and every individual obstacle intently. In other tests, the researchers only offered advice about tackling the course as a whole. When subjects focused on each obstacle intently, the researchers found that they were far more likely to fail the obstacle than if they had approached the course as a whole.
The researchers hooked patients up to machines that gave them moment to moment pictures of their brains as they went through the obstacle course and found that anxiety centres were far more active when each obstacle was tackled individually as opposed to the obstacle course as a whole. The failing was caused by the individuals looking away from the obstacle too early and stepping too soon, causing them to miss the obstacle. The high anxiety caused an obstacle fixation problem, where by increased conscious control lead to increased error.
While the researchers offered this as the reason why people who fall are more likely to suffer from further falls (they fixate and agonize too much on the step or the obstacle and it makes them fail in their foot placement), this could translate to performance as well; fixating too much on the individual parts of a task can mean that the task as a whole may suffer.
Take Away
Fixating too much on a specific task that is part of a whole can create an increase in error for that specific task and, as a result, the whole. Take obstacles and challenges as a whole to decrease anxiety and increase performance. This is especially the case for elderly people who have suffered a fall and are anxious about another fall.
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