August 7 2020

Photo by Victor Freitas on Unsplash

As health professionals it is easy to take some of our knowledge for granted. We might assume that the benefits of physical activity are well known. However, making assumptions is dangerous business. One of my schoolteachers once told me that if you assume, you make an ass out of u and me!

So take it from the World Health Organisation (WHO), physical inactivity is a big problem. You can check out the risks of physical inactivity and recommended doses of physical activity across the lifespan on the WHO Physical Activity page. As an example, lets look at the WHO recommendations for the 18-64 yr old age group.

  • At least 150 minutes of moderate intensity, or 75 minutes of vigorous intensity physical activity per week (or an equivalent combination of the two)
  • Increasing moderate intensity activity to 300 minutes per week for additional health benefits
  • Muscle strength training on 2 or more days per week

Physiotherapists are in a position of responsibility to encourage our clients to follow guidelines like these. Across the general population there are exercisers, ex-exercisers, non exercisers, and those that fall somewhere in the middle. Everyone’s an athlete, it’s just that some are in training, others are not!

So what’s the best way to get started with exercise? What’s the best way to manage physical activity levels to avoid injury? In recent years there has been rapid growth of research into the monitoring and analysis of physical activity levels in athletes. Some of this information may be of use when thinking about general management of physical activity levels.

Disclaimer – Where research is completed with a specific population group e.g. elite athletes, it isn’t always possible to extrapolate the results to the general public. Practically, if a premise makes scientific sense it can be tested in clinical practice.

Load Management in Athletes

Sports Science and Sports Medicine researchers have taken to monitoring athlete training loads in an attempt to maximise performance and minimise injury. What they have looked for is the happy middle ground between under and over training. Enter the acute:chronic workload ratio (ACWR). Put into simple terms, your chronic workload is the rolling average amount of activity completed in the last 3-6 weeks, a measure of your fitness. Your acute workload represents this week’s training or activity. Your fitness level is what you’re prepared for, versus the workout you choose to take on this week. If this week’s chosen activity is close to your rolling average, then performance is likely to be good, whereas if the activity level is far above the rolling average, injury risk goes up. You really are only as good as your last month’s training!

Researchers have found the sweet spot is in keeping the acute:chronic workload ratio between 0.8-1.3. This basically means in order to keep injury risk low and performance high you need to stay within a range of not more than 20% decrease compared to average (so as not to lose fitness) and to keep increases less than 30% compared to average (to avoid injury).

General Physical Activity Application

Photo by Vicky Sim on Unsplash

But what if you’re not an athlete? How does this apply to the punter in the street? Let’s say you’re a bit out of shape, haven’t been exercising and want to start walking to help with your arthritic knee (or maybe you want to have a crack at pushing some big boulders around!). If you haven’t walked for months you have no rolling average fitness beyond your day to day activity (although this might still be pretty good for some). Jumping straight into 7 days a week walking for 60mins is likely to shoot your ACWR through the roof! The cartilage in your knee is unlikely to be ready for the new loading, and may begin to give you pain.

Let’s say you were more graded in your efforts to become more active and you took three 20min walks per week for a month. You have done a few of the strength exercises your physio gave you as well, the knee feels good and you’re feeling puffed up about yourself. This week you have a crack at three 40min walks. This scenario has your ACWR at 2, well above the recommended maximum of 1.3 (60mins walking average vs 120mins walking this week). You might get away with it and not feel too bad, but your tissues (bones, ligaments, muscles and tendons) haven’t had the time to adapt to this new level of loading. You might not have a pain immediately, but you have increased your risk of injury for a prolonged period, possibly even the next month.

Our bodies like consistent levels of activity, with graded increases where possible to increase our strength and fitness. Where the trouble can start is with rapid spikes in activity levels, or return to normal levels after a break, e.g. being unwell or busy, closed gyms etc

Unfortunately, this type of trouble can lead to a visit to the physio, whether it is the result of a big day in the garden on the first sunny weekend in spring or the ‘new year, new me’ enthusiasm of January visits to the gym!

Hopefully an awareness of the ACWR concept can help in the planning of your physical activity levels. The adage ‘use it or lose it’ is unfortunately also the rule. If we don’t keep consistent with activity, we lose our strength and fitness. Finding the Goldilocks level should serve well – the ‘just right’ amount of activity – not too big with the increases, and not dropping off too much either. And one more piece of advice to finish off, a little bit of wisdom from a patient – your goal for going to the gym should be to be able to go the next time. Going too hard and hurting yourself is a sure way to not be able to build on your successes!

If you have any concerns about your physical activity levels or would like some advice on how to safely build up, do get in touch. We love nothing more than helping you achieve your fitness and well being goals!

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