Which type of athlete are you?
The one who never stops training? The athlete who tries to out grind the competition?
Or are you the one constantly looking for a way to hack the system?
Which is better?
From a health perspective, which increases injury risk: overtraining or undertraining?
The answer? Both.
Working way too hard is as detrimental as not working hard enough.
Please note that we’re talking about non-contact, overuse injuries here. These are preventable. Contact injuries are a different story. We don’t have as much control over what happens when two players collide on the soccer field or basketball court.
Find Your Training Balance
The best performance programs aim for a “sweet spot” where the training is intense enough to make athletes better, faster, and stronger, but not so much to cause injury.
Regardless of the sport, we should look at two factors when building training programs:
- The intensity of workouts or movements. This is also known as “load.”
- How fast the intensity “ramps up.”
Let’s define “training” a bit further:
- Acute training is the amount of workout volume in the past week.
- Chronic training is the average amount of workout volume over the past 4 weeks.
Think of acute training in the same terms you’d think about fatigue. How tired are you from your training sessions or workouts over the past week? Chronic training involves looking back on the past few weeks and reflecting on “how fit you are” from those workouts.
Objectively comparing how you feel now to how you have felt over the past three to six weeks gives interesting data on how ready you are for competition. For example, I coach a group of adult distance runners, helping to prepare them for half and full marathons over the course of a 15 week cycle.
These athletes run their peak mileage three weeks before race-day. The remaining time leading up to competition is called a “taper” designed to decrease their acute training load. The goal is to feel fresh-legged at the starting line but still have the capacity to run 13.1 or 26.2 miles.
Taper weeks can be a source of stress for athletes who worry they’ve not run, trained, or lifted at their usual high volume, but there is scientific reasoning backing this strategy. If an athlete has taken it easy the week before a race but has a good base of mileage throughout training cycle, they will still be well-prepared for race day.
This athlete’s acute training would be classified as low, as they would be well-rested. Their average chronic training, however, is high because the athlete built a base of endurance over the weeks prior.
The Role of Training Load
Load is a measure of the intensity of a training session or how much stress that session placed on the body. Three things define this for an athlete:
- External training load: “work” or “volume” (total distance run, amount of weight lifted, number of sprints, jumps to rebound a basketball, collisions in football, etc…)1
- Internal training load: the body’s response to the training (rate of perceived exertion, heart rate, blood lactate, oxygen consumption)1
- Individual characteristics of the athlete: age, experience, injury history, physical capacity
To summarize: training outcome = external load + internal load + individual characteristics of the athlete.
All these factors are important in determining the effect of a given workout. The same external load could have a different internal effects based on the individual. For example, how a 21-year-old trained collegiate soccer player would respond to a 4 mile workout versus a 40-year-old athlete that started running a few weeks earlier.
The workout is too intense for the 40-year-old and could increase their risk for injury. Conversely, the run would be “too easy” for the collegiate athlete with little to no cardiovascular gains.
An external load could also have varying effects on the same athlete. A tough week of training often renders an athlete feeling tired, stressed, and fatigued. If proper recovery measures are not taken, performance can suffer on workouts.
It's also important to understand the effect of “life” factors on training: emotional disturbances, illness, stress, or recent training history. Respect these factors and modify workouts accordingly.
Tracking External Load
For endurance athletes like runners, swimmers, and cyclists, this is easy to monitor. GPS watches can log distance and speed covered.
Most elite/pro athletes now use GPS-based sensors to track movements and training specific to their sport. For example, the number of jumps in volleyball, collisions in rugby or football, strokes in swimming, or sprints per game in soccer. Coaches can scale up or down the training load based on how much a particular athlete had in competition.
Since GPS watches are not useful with weight training, calculate the load like this:
External load = the number of repetitions x kilograms of weight lifted 3
Tracking Internal Load
Rate of perceived exertion is one of the easiest ways to track internal training load. Rate the intensity of the session on a scale of 1-10. Multiply that rate by the length of the training session in minutes:
Internal load = RPE (scale 1-10) x minutes of training
This score could also be called “exertional minutes.” Researchers are still collecting data on different measures of “high” or “low” exertion for various sports. For now we consider a score of 300-500 in football players as a low intensity training session and 700-1000 is higher.1
Heart rate or VO2 max multiplied by training minutes would also be another way to track internal load. Measuring blood lactate concentration is a technical and invasive method, but is a unit of measure.
There are other scales used for elite athletes like the Recovery-Stress Questionnaire that tracks mood, stress level, energy, soreness, sleep, and diet. The total score indicates the athlete’s well-being so that coaches or strength and conditioning experts can adjust workouts accordingly.
The Role of Individual Athlete Characteristics
Studies on rugby and Australian football players show that age influences how athletes respond to conditioning programs. Research also shows older athletes are at higher risk for overuse injuries.
In terms of these studies, one must ask if the injury risk is from workouts that are too intense, or is risk elevated because older athletes may have a greater accumulation of prior injuries? Research also shows that history of past injury is a major risk factor for a new injury.
Regardless, a training program should be individualized to the athlete’s age, experience, injury history, and overall physical capacity.
Calculate Your Training Load
Tracking external and internal load, or acute and chronic training can help determine if you are an optimal zone for your goals. More importantly, it can alert for elevated injury risk. Consider the training example used earlier:
“Peak weeks” for a half marathoner (weeks 8 -11 of a 15-week program):
- Week 8: 21 miles
- Week 9: 23 miles
- Week 10: 25 miles
- Week 11: 30 miles
- Acute load (mileage week 11) = 30 miles
- Chronic load (average mileage 4 weeks prior) = 24.75 miles
Now, take the acute load (30) and divide by the chronic load (24.75) to get a ratio:
Acute load ÷ chronic load = acute:chronic load ratio (30/24.75 = 1.21)
“Taper weeks” for the same race (the last few weeks before competition):
- Week 12: 24 miles
- Week 13: 23 miles
- Week 14: 18 miles
- Week 15: Race Week
- Acute load (mileage at week 14) = 18 miles
- Chronic load (average mileage of the 3 weeks prior) = 21.67
Again, calculate the ratio:
Acute load ÷ chronic load = acute:chronic load ratio (18/21.67 = 0.83)
Research shows the “sweet spot” or optimal zone for training is a ratio between. 0.8 and 1.3.1,2
The runner is in the optimal training zone during the “peak weeks” above has built enough of a mileage base to stay in that zone through the taper and entering race week.
Research has also shown that a ratio above 1.5 is a “danger zone” for training. Increased injury risk is higher in the weeks after training at this kind of load.
How many of us have been in this situation? We feel great on a particular training week and continue to ramp up the intensity. As workouts get harder, initially we feel invincible. Then, the wheels fall off. An injury happens “out of nowhere,” leaving us wondering what went wrong. I can’t tell you how many times I’ve heard, “but I felt so GOOD, Carol! I don’t know what happened?!”
Unfortunately this is an easy trap to fall into, but monitoring the ratio of acute to chronic load can help.
But maybe you don’t run. You – lift weights, CrossFit, play soccer, insert sport of choice. How do you track your training?
The same concepts apply:
- Calculate the acute training load over the past week (number of repetitions x kilograms of weight lifted). Or total the number of sprints, minutes of soccer practice, etc.
- Find the chronic training load (average over the past 4 weeks).
- Divide the acute load over the chronic load and compare to the figure above.
- Remember to take into account internal training factors and individual characteristics.
The Bottom Line of Volume Training
- Intensity matters. Both overtraining and under-training put athletes at risk for injury. A training program must get the athlete ready for the demands of their sport, but the coach and athlete need to understand it may take a several weeks to get to this point.
- Sudden increases in training intensity puts athletes at risk for injury. Monitor acute training (how fatigued you are over the course of a week) and compare it to chronic training (how “fit” you have been over the past few weeks).
- Monitor the body’s response to training. The internal training load. Use rate of perceived exertion x number of minutes spent training. Think about other factors—age, stress, sleep, etc. These are all important to help determine what your training load should look like.
1. 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.
2. Blanch P, Gabbett TJ. Has the athlete trained enough to return to play safely? The acute:chronic workload ratio permits clinicians to quantify a player’s risk of subsequent injury. Br J Sports Med. 2016 Apr;50(8):471-5. doi: 10.1136/bjsports-2015-095445. Epub 2015 Dec 23.
3. Bourdon PC, Cardinale M, Murray A, Gastin P, Kellmann M, Varley MC, Gabbett TJ, Coutts AJ, Burgess DJ, Gregson W, Cable NT. Monitoring Athlete Training Loads: Consensus Statement. Int J Sports Physiol Perform. 2017 Apr;12(Suppl 2):S2161-S2170. doi: 10.1123/IJSPP.2017-0208.
4. 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.
5. Gabbett TJ. The development and application of an injury prediction model for non-contact, soft-tissue injuries in elite collision sport athletes. J Strength Con Res 2010;24:2593–603.