Critical concepts in reducing running-related injuries. Part 1

Running workload and bodyweight

Introduction

In my last post, we took a dive into running concepts and foot strike patterns. We concluded two significant points 1. There is unlikely to be an optimal foot strike pattern, which can be applied to all runners and 2. By understanding how the body absorbs and generates forces during running, we can prepare and maintain sensibly, maximising the enjoyment of running and reduce injury risk.

Running injuries tend to develop slowly in response to accumulative loading and eventually reach a tipping point, ultimately resulting in cessation of running and pain. There appears to be an increased risk of this happening to beginners, competitive distance runners and speedsters with the majority of people in between these extremes coping well (1) Fig 1. Besides running level other risk factors which limit the body’s ability to adapt or cope with the high-impact demands of running also need consideration Fig 2.

Fig 1.

It is only logical for a similar increase in running habits an older, sedentary, beginner runner with excess body fat and a history of injuries has a higher risk of injury compared to their younger, physically active and healthy counterpart. Therefore, if you are one of the runners who meet some or all of these simplistic higher risk criteria then you may benefit from understanding the modifiable risk factors I am going to discuss.

Fig 2.

Four critical and modifiable areas include running workload, body weight, muscle preparation and running form. For the risk aversive, you will want to focus on all of these however, in today’s post I will focus on running workload and body weight, which in my opinion are critical to understand for the high-risk beginner and irregular runner.

Running workload

Runners can typically increase their distance and speed quicker than their bones, tendons, joints and muscles can adapt and recover. Therefore, it is not a surprise that training error is one of the greatest risk factors for developing a running-related injury (2). Many freely available online resources provide running workload advice and plans, which runners utilise. Unfortunately, these generally lack sufficient evidence-based support and vary widely in their recommendations to runners potentially creating confusion or false confidence.

Through education of running workload, runners can greatly reduce training error and subsequently the risk of developing a running-related injury. Running workload is simply the distance covered (volume) and how quickly that distance was covered (intensity) within an individual session. For runners with a specific goal, particularly large increases in distances and/or speeds scheduling the frequency and progression of your running (a running cycle) is important to reduce the risk of injury.

It is unclear whether increasing running distances or speeds presents the greatest risk of developing a running-related injury. However, one study, which followed several hundred experienced recreational runners, found no difference in absolute risk between groups focusing on either increasing volume or intensity (3). Two important themes to emerge from this study however were even modest increases in volume (6km over 16 weeks) and sudden changes in intensity, increased injury risk Fig 3. This is important as many online resources far exceed the percentage changes within this study and furthermore are applied by beginner and irregular runners.

Fig 3.

Irrespective of your training goals, managing volume and intensity of your running and planning cycles to promote adequate recovery for the body to adapt is likely to reduce your injury risk. For the low-risk runner, this doesn’t require much thought other than to avoid sudden changes and gradually increase your running distances and or intensity.

For the high risk or risk aversive runner, however, the following table provides guidance on how to approach planning a running schedule, which may be adapted to suit your risk tolerance and personal circumstances. At the end of this post, I have provided a couch to 5km training plan for the high-risk beginner/irregular runner based on the principles we are discussing and as an example.

The main points to consider are the higher risk you are the longer your training cycles should be and the progression made within and between cycles should be modest. Remember we want the body to adapt and recover sufficiently. Calculating progression of volume is relatively straightforward with 10% weekly increases frequently cited (4). However, for those at greater risk, you may consider limiting your progression during a cycle to a maximum of 30% with a 10% tapering for a week or two before progressing into a new cycle Fig 4.

Fig 4.

Intensity is the speed at which a distance is covered measured by time however, this does not reflect the effort required to achieve it. A simple method to avoid sudden changes in intensity is to simply record time and perceived effort after a run on a scale of 0 (easy) – 10 (Extremely hard) and remain consistent within a cycle. This is likely to be sufficient for most runners.

For the more conscientious runner measuring your time and average heart rate is a more accurate method of recording intensity. Running is an aerobic activity, which can easily increase your heart rate by approximately 50-70% of your maximum, which is between 150-210 depending on fitness and age (5). Fit runners can sustain long periods of running at 70-85% of their maximum heart rate. Operating within these boundaries and keeping your average heart rate consistent during cycles will allow you to monitor for sudden changes in effort and potentially reduce future injury risk.

Bodyweight

Running is a great way to increase energy expenditure and thus burn calories. For example, a 90kg person running at 12kph for 1 hour (covering 12km) could burn approximately 1000 calories. This is somewhat more appealing from a weight management perspective than a 90kg person walking for 1 hour at 4kph (covering 4km) and burning 270 calories.

However, it is not as simple as that, for one not many 90kg individuals can run for an hour. Moreover, if they could the body will compensate by increasing hunger or fatigue afterwards. The result is either an increase in calories consumed and/or sedentary behaviour to maintain an energy balance, consequently leading to neutral energy expenditure and thus minimal to no weight loss.

This is frustrating as excess body fat is a problem with many individuals at a higher risk of developing overuse injuries to tendons, bones and joints (6). The reason for this is complex but increases in bodyweight result in greater impact forces and higher levels of muscle activity during running potentially leading to accumulative micro-trauma over time (7).

Normal body fat percentage varies based on age and gender. For a precise measurement, a dexa scan can be employed. However, a surrogate test called the BMI can be utilised to give the non-athletic, non-muscular individual an idea of their body fat levels. A BMI calculator and ranges can be found here.

There is no ideal BMI to start running or reduce your risk of developing a running-related injury. However, if you have a high BMI you may consider yourself at a higher risk. To manage this risk planning your running cycles and preparing your muscles is important. Furthermore, for the risk-averse or easily fatigable runner, you may even consider losing body fat prior to starting running.

Unfortunately, there is no magic pill or potion to lose body fat (yet!). However, increasing the need to utilise body fat as an energy source is likely to be the most effective way to achieve this. The hormone insulin is the primary regulator of fat storage and inhibits its mobilisation (8). Within our diets, certain calories lead to excess insulin secretion and ultimately sub-optimal fat metabolism. Energy-dense highly refined carbohydrates (sugars, starches) are the leading suspect of this increase in insulin levels (9).

Interestingly, excess body weight and fat are not huge problems in non-industrialised communities influenced by modern culture, which may partly be explained by less access to refined carbohydrate consumption. Furthermore, the necessity to perform regular physical activity such as forage for food, dig, hunt, build and maintain habitats is greater in these communities thus expending more energy than more sedentary individuals in modern society. This regular physical activity may also explain why on average non-industrialised individuals are stronger than their age-matched counterparts in modern cultures (10).

Modern society and all its conveniences may well be making us less physically prepared to run. For high-risk runner wishing to lose weight reducing refined carbohydrates and increasing, physical activity levels may prove beneficial over a period of weeks and months. Subtle changes in habits such as walking rather than driving, using the stairs and not the lift can accumulate meaningfully over time to weight loss and increases in strength. For instance, if our 90kg person increases their walking habits by a modest 12km a week (14-16 thousand steps) for a year this will result in approx. 38,880 extra calorie expenditure, equivalent to nearly 5kg of fat. When combined with an appropriate diet this is a meaningful and sustainable change.

In my next post, I will discuss specific physical activity in the form of exercises and running form to help prepare your body for the rigorous and energy expending activity of running. Thanks for reading and feel free to reach out if you would like to discuss your running workloads.

Here is an example couch to 5km running schedule for a high-risk beginner runner who is concentrating on increasing distance and is not concerned about time/speed.