Measuring Load
The most common way to measure workload is by calculating the acute workload, which is the time/distance covered in one week, and then dividing it by the average time/distance covered over the preceding 4 weeks, known as the chronic workload.
Research suggests that maintaining load variations of 80% to 130% may result in the lowest risk of injury. If you maintain the exact same training program week on week, your chronic workload and acute workload will always total 1 (or 100%). When the chronic workload is higher than the acute workload, the ratio will be lower than 1, potentially leading to less risk of injury but possibly impeding fitness and exercise development. Conversely, if the acute workload is higher than the chronic workload, the ratio will be higher than 1, and if reaching up to >1.5 (or 150%) can indicate an increased risk of subsequent injury.
The graph visually represents the concept explained above.
To minimise the risk of injury, the cumulative load should aim to maintain the acute:chronic workload ratio within a range of approximately 0.8–1.3 (80-130%), which is represented by the green-shaded area (referred to as the ‘sweet spot’).
The red-shaded area (referred to as the ‘danger zone’) represents acute:chronic workload ratios where the risk of injury is high.
Progressing Fitness
Remember to progress your fitness gradually in order to increase exercise tolerance while minimising the risk of injury. It’s advisable to increase your workload by approximately 30% week on week, and over the course of the month. If you’re unsure, please consult your physiotherapist for guidance.
Example: If you’ve been consistently exercising over the past month with a base of 5km in week 1, 10km in week 2, 10km in week 3, and 3km in week 4, with each week being an acute workload, the total chronic workload for that month is 7km (28 divided by 4). To stay in the ‘sweet spot’, the workload for the next week should be between 5.6km (minimum) and 9km (maximum). Increasing the workload by 30% to a maximum of 9km is considered a safe overload, while anything above 9km or below 5.6km may increase the risk of injury.
Physiological Threshold Signs
In conjunction with workload ratios, we also consider your overall ‘wellness’. Signs that you have reached a physiological threshold include feeling run down, fatigued, experiencing poor sleep, cold and flu symptoms, cold sores, and/or thrush in women, all of which indicate that you should rest.
Conclusion
Injuries affected by poor suboptimal load management can include, but are not limited to, shin splints, tendon pain, plantar fascia pain, ITB syndrome, patellofemoral/knee pain, bursitis, muscle strains, and stress fractures.
Having a tailored load management plan supervised by our physiotherapists will help keep you active for longer while achieving your exercise goals.
References:
Image taken from – Gabbett TJ. The training-injury prevention paradox: should athletes be training smarter and harder? Br J Sports Med. 2016 Mar;50(5):273-80. doi: 10.1136/bjsports-2015-095788. Epub 2016 Jan 12. PMID: 26758673; PMCID: PMC4789704.
Maupin D, Schram B, Canetti E, Orr R. The Relationship Between Acute: Chronic Workload Ratios and Injury Risk in Sports: A Systematic Review. Open Access J Sports Med. 2020 Feb 24;11:51-75. doi: 10.2147/OAJSM.S231405. PMID: 32158285; PMCID: PMC7047972.