Many of us are keen to shed those extra winter kilos, embrace the warming weather and start dancing our feet down the asphalt path. However being too keen to rediscover our summer bodies or achieve that personal best time at Parkrun can predispose ourselves to a variety of injuries.
So how can we prevent this?
In the sporting world researchers have studied the relationship between training volume, intensity and frequency on injury. They discovered that despite an increase in performance with increases in training loads, there is a higher incidence of injury and illness associated with these higher training loads.
So how do we know when too much is enough?
There is no golden number, nor a ‘one size fits all’ approach but the evidence from Tim Gabbett (2016) does suggest there is a ‘sweet spot’. Gabbett and colleagues1 investigated the relationship in what he describes as acute workload (the accumulation of physical stress in one week) versus chronic workload (the accumulation of physical stress over 4-8 weeks). He discovered there is an increase in injury risk if the acute to chronic workload ratio exceeds 1.3. This means, if you have averaged 20km per week for the last 6 weeks and then increase your running average to 30km the following week, your acute to chronic workload ratio would be 1.5 and consequently you would be increasing your risk of further injury.
Figure 1: Acute:chronic workload ratio data. The green-shaded area (‘sweet spot’) represents acute:chronic workload ratios where injury risk is low. The red-shaded area (‘danger zone’) represents acute:chronic workload ratios where injury risk is high. Sourced from Blanch and Gabbett1.
Other studies2,3 have extended on this concept by attempting to account for things like mood, stress level, energy, sleep, diet and heart rate. They use a ‘rating of perceived exertion’ to help quantify these internal loads and thereby more accurately measuring the physiological and psychological stresses imposed during exercise. They use a numerical scale (Figure 2) multiplied by session minutes to calculate the total workload or ‘exertional minutes.’ For example, if a person’s rated perceived exertion for a particular session was rated 6 and they trained for 30 minutes, their ‘exertional minutes’ would be 180 arbitrary units for that particular day. Using this formula, these studies2,3 have found that a spike in weekly training loads between 10-15% is associated with an increased risk of injury between 21% and 49%. This supports Gabbett’s1 acute to chronic workload ratio findings.
Figure 2: Rating of perceived exertion (Source: sportsperformancetracking.com/blogs)
So as summer fast approaches and our desire to re-discover our beach-bods motivates us to exercise more, consider the research outlined above. Poor training load prescription and management is a risk factor for injury but by monitoring your workload ratio or exertional minutes you will minimize injury risk and improve overall performance. So, grab your smart watches and start pounding the pavement and remember, training harder is not always smarter!!!
Blog Credit: Andrew Scott
1. Hulin BT, Gabbett TJ, Lawson DW, et al. The acute:chronic workload ratio predicts injury: high chronic workload may decrease injury risk in elite rugby league players. Br J Sports Med 2016;50:231–6
2. Piggott B, Newton MJ, McGuigan MR. The relationship between training load and incidence of injury and illness over a pre-season at an Australian Football League club. J Aust Strength Cond 2009;17:4–17.
3. Rogalski B, Dawson B, Heasman J, et al. Training and game loads and injury risk in elite Australian footballers. J Sci Med Sport 2013;16:499–503.