19 Aug The Key to Progressive Overload
You hear it all the time – whenever someone talks about starting a weightlifting routine, running their first marathon, or starting an off-season workout plan, the advice is always the same: “start slowly”; “progress gradually”; “don’t do too much, too soon”. You might even hear this from a doctor when returning to sports after an injury or surgical procedure. But how much is too much? And how soon, is too soon? No matter what you are doing, the art of gradually progressing is difficult. After reading this article, you will be able to answer the question of what is progressive overload? In addition, you will familiarize yourself with science-based strategies for progressive overload that will ultimately allow you to reach your fitness goals while minimizing your risk of injury!
What Is Progressive Overload: How Do Injuries Occur?
Few if any movements are inherently dangerous. Rather, injuries usually occur from performing a task we are not prepared to perform, for a length of time we do not have the endurance for, or with a load we are not ready to bear.
As physical therapists, we see this all the time in our patients. At New Year’s when a patient tries to meet their yearly weight loss goal in the first month. Or on the first day of spring, when a patient moved from hibernation to a half marathon. You see it too! Everyone knows not to waste a fantasy football draft pick on the running back who held out of training camp, because he is very likely to get injured! So what is the key to progressive overload? The key is a calculation called Acute:Chronic workload ratio.
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What Is Progressive Overload: Acute:Chronic Workload Ratios (ACWR)
An acute:chronic workload ratio or ACWR is a calculation that compares the workload (i.e. activity level) a person is prepared for, to their current workload. It does this by comparing the workload over the last week (acute workload) to the workload over the last month (chronic workload), with some higher-level math to provide additional weight to the more recent workout sessions.
Essentially ACWR is an indicator of how prepared you are for the work you are doing. Think of comparing your level of fatigue to your level of fitness. Thus, a higher number indicates that you are performing a workload you are not ready for.
Using ACWR To Your Advantage With Progressive Overload
For example, if ACWR = 2.0 or 200%, this indicates that the workload over the last week is double the average workload over the last month. As you might guess an ACWR of 2.0 puts you at a very high risk of injury!
Hulin et al. published one of the first papers detailing the increased injury risk that results from higher ACWR in a 5-year study of elite cricket fast bowlers. They measured external workload using the number of balls bowled and estimated internal workload by combining the training session duration with the self-reported rating of exertion on a scale from 0-10. Surprisingly, they found no link between ACWR (whether internal or external) during the week that the measure of acute workload was taken. However, they found that athletes were at higher risk of injury during the week after a spike in ACWR! In layman’s terms: if you overdo it at the gym this week, you are more likely to get injured at the gym next week. The graph below details the correlation between injury risk and ACWR the week after acute workload was measured. As you can see, the greater the ACWR, the greater the risk of injury.
Fortunately, this correlation holds true for internal workload as well as external workload. Thus, if you feel like you are working twice as hard as you have all month, you are putting yourself at an increased risk of injury next week.
So, How Much Is Too Much?
In the graph above, the asterisk indicates a statistically significant increase in the likelihood of injury. As you can see, the first asterisk is present at an ACWR of 1.5 or 150%. Thus meaning that you are putting yourself at an increased risk of injury when your weekly workload is greater than or equal to 150% of your average monthly workload. To be even more specific, when assessing internal workload via a combination of perceived exertion and duration of the training session, this study found that an ACWR of >1.5 DOUBLED your risk of injury the following week. While high-level athletes may occasionally need to train or perform at an ACWR of >1.5, the average weekend warrior can decrease their risk of injury by taking care to minimize these spikes in workload.
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Is There Anything I Can Do To Avoid Injury Despite A Spike In Workload?
Firstly, it is important to be clear here: While an ACWR >1.5 increases your likelihood of injury, this does not mean that you will get injured, or even that you are likely to get injured when working in this range! Only that you are more likely to be injured than you are if working with at lower ACWR. Secondly, there are a number of other factors that will affect your tolerance to a spike in workload, independent of your ACWR. Surprisingly, one such factor is chronic load, in isolation. As you can see in the graph below, as chronic load increases, your likelihood of injury decreases.
Simply put, the more exposure to a load you have, the more ability you have to withstand a spike in load. Thus, the goal is not the absence of load, but rather the gradual progression of your chronic load, to allow you to withstand spikes in chronic load. To progress your chronic load, you will likely often need to train at an ACWR >1.0! Fortunately, some other factors have been identified which affect injury risk as well as training adaptations, these include:
- Sleeping 8 hours a night
- Stress-related personality traits
Thus, while ACWR is an important consideration for injury risk, it is not the only factor to consider (2)
How Do I Monitor My Workload?
While the seminal work in this area was done with elite cricket players utilizing the discrete measure of balls bowled to determine external workload, subsequent studies have found similar results in a variety of sports and activities. These include:
- Australian football
- American Football
- Multisport athletes
Some measures of external workload which have been used include:
(1) total distance
(2) low-speed distance
(3) moderate-speed distance
(4) high-speed distance
(5) very high-speed distance
(6) player load measured via wearable accelerometers.
The distinction between these measures, and the technology required to collect them, may be important for elite-level athletes. However, for the everyday athlete the use of internal workload, described above and well established by the literature, should suffice.
What is Progressive Overload: Distance Running
While monitoring your internal workload for spikes in ACWR may be valuable, distance running presents us with additional evidence-based methods for decreasing injury risk. Running is often a go-to method of exercise for those trying to lose weight. It’s simple, accessible, requires no travel time or gym membership, and everyone can do it! Unfortunately, the high rates of injuries among novice runners can prevent many people from reaching their fitness goals. A Danish study evaluating novice runners with a BMI between 30-35 found that runners who started training at 6km/week rather than 3km/week had nearly a 50% increased risk of sustaining overuse-injury symptoms over the first 4 weeks. Thus if you are starting a running program in an effort to lose weight, it may be wise to start with 3km/week for the first month. For reference, 1 km is equal to just over half a mile. Thus 3 sessions of jogging ½ mile would be a good starting place with a low risk of injury.
For more advanced runners: a study evaluating experienced runners training for a half marathon found that increases in weekly running distance of >20% increased risk of injury by 22%. Thus when planning to work up to the goal of a half marathon or marathon, it would be wise to leave enough time to avoid weekly increases of >20% in mileage. Additionally, lower body strength has been found to be a protective factor when workload does spike.
What Is Progressive Overload: What About Returning To Running After An Injury?
Even when monitoring your load efficiently, injuries happen. And the biggest risk factor for future injury is a previous injury. Thus, it is really important to make sure you fully rehabilitate an injury before returning to running. While you may need to take some time off from running after an injury, research has shown that early movement and rehabilitation leads to much better outcomes. In fact, the difference between starting rehab 2 days after an injury vs. 9 days has been shown to help athletes return to playing 3 weeks earlier, without any increased injury risk.
More research is coming out in this area every day and recently some researchers have called into question the value of ACWR calculations (6, 7). However, for the average fitness enthusiast, following these keys to progressive overload should keep you in the gym and off the sideline:
- Track the overall difficulty of your workouts with a rating of 0-10
- Monitor the duration of your workout in minutes.
- Proceed with caution if your weekly workload is >150% of your monthly workload.
- Take time to gradually build up to a high chronic workload.
- Get 8 hours of sleep, take mental health seriously, and don’t push through workouts when you feel like these factors are holding you back.
- If starting a running program for the first time, consider starting with 3km/week.
- If training for a marathon or half marathon, try to avoid weekly increases of mileage > 20%.
- Hulin BT, Gabbett TJ, Blanch P, Chapman P, Bailey D, Orchard JW. Spikes in acute workload are associated with increased injury risk in elite cricket fast bowlers. Br J Sports Med. 2014;48(8):708-712. doi:10.1136/bjsports-2013-092524
- Murray NB, Gabbett TJ, Townshend AD, Blanch P. Calculating acute:chronic workload ratios using exponentially weighted moving averages provides a more sensitive indicator of injury likelihood than rolling averages. Br J Sports Med. 2017;51(9):749-754. doi:10.1136/bjsports-2016-097152
- Gabbett TJ. Debunking the myths about training load, injury and performance: empirical evidence, hot topics and recommendations for practitioners. Br J Sports Med. 2020;54(1):58-66. doi:10.1136/bjsports-2018-099784
- Bertelsen ML, Hansen M, Rasmussen S, Nielsen RO. THE START-TO-RUN DISTANCE AND RUNNING-RELATED INJURY AMONG OBESE NOVICE RUNNERS: A RANDOMIZED TRIAL. Int J Sports Phys Ther. 2018;13(6):943-955.
- Damsted C, Parner ET, Sørensen H, Malisoux L, Hulme A, Nielsen RØ. The Association Between Changes in Weekly Running Distance and Running-Related Injury: Preparing for a Half Marathon. J Orthop Sports Phys Ther. 2019;49(4):230-238. doi:10.2519/jospt.2019.8541
- Impellizzeri, Franco & Woodcock, Stephen & Coutts, Aaron & Fanchini, Maurizio & Mccall, Alan & Vigotsky, Andrew. (2020). Acute to random workload ratio is ‘as’ associated with injury as acute to actual chronic workload ratio: time to dismiss ACWR and its components. 10.31236/osf.io/e8kt4.
- Wang, C., Vargas, J.T., Stokes, T. et al. Analyzing Activity and Injury: Lessons Learned from the Acute:Chronic Workload Ratio. Sports Med 50, 1243–1254 (2020).
- Bayer ML, Magnusson SP, Kjaer M. Tendon Research Group Bispebjerg. Early versus delayed rehabilitation after acute muscle injury. N Engl J Med 2017;377:1300–1.
About The Author
[P]REHAB Writer & Content Creator
Tommy Mandala is currently a Doctor of Physical Therapy and Board Certified Sports Clinical Specialist at the Sports Rehabilitation and Performance Center at Hospital for Special Surgery in New York City. Prior to that he completed a sports residency at the University of Delaware where he had opportunities to work with their Division I baseball team, as well as the Philadelphia 76’ers NBA G-league affiliate, the Delaware Blue Coats. A former high school baseball player, this experience drove his interest in treating the throwing athlete and led him to pursue a rotation at Champion Sports Medicine in Birmingham, Alabama to learn from leading baseball researchers in the American Sports Medicine Institute. While Tommy has a special interest in throwing athletes and ACL rehab, he believes that everyone should train like an athlete. As the son of an FDNY firefighter, he also has a passion for treating the occupational athlete. One of his favorite aspects of his job is teaching patients the proper form to allow them to continue doing the things they love in spite of an injury.