Endurance training is hard work. As such, it requires a high level of motivation, which for most athletes comes partly from an expectation that their training will yield results. But expectation alone won’t motivate to keep working hard. Athletes want proof that their training is yielding results, not just on race day but throughout the process. Where should they look for this proof?
The obvious answer is measurement—specifically, objective indicators of fitness. If your VO2max or your critical velocity or your lactate threshold or another scientifically validated measure of endurance fitness is increasing, your training program is working. But it’s not always easy to obtain reliable measurements of these physiological values. You must either rely on formal testing, which can’t (or shouldn’t) be done too often, or trust the estimates generated by some wearable device, and the expert consensus is that these estimates are not terribly reliable.
What’s more, even if quantitative indicators of fitness could be measured every day, the numbers wouldn’t trend upward every day. Getting fitter is at most times a slow process, especially for athletes who’ve already established a strong base of aerobic conditioning. Those hungry for proof that their training is working would find little satisfaction in a perfect-information scenario, where a godlike measurement device allowed them to know their precise VO2max and lactate threshold and whatever at all times. Weeks might pass before this device—like the watched pot that never boils—showed any change in the numbers.
Some athletes, not content to wait for the numbers to change, try to make them change. I call this the progress trap. An example is Jessie, a runner I coach who likes to train by heart rate. In the beginning, Jessie got fitter quickly, and the numbers proved it, her pace at any given target heart rate getting faster and faster, which made her happy. But the trend couldn’t last forever, and when she started experiencing runs in which, perhaps due to fatigue imposed by the harder workouts she was doing, she actually needed to slow down to stay in the right heart-rate zone, she refused to do so. The result was that she stopped improving and started to slide backward.
There are two main pieces of advice I give to athletes like Jessie. One is to relax and trust the process. I’ll say more about this in a later chapter. My other advice is to look for proof that training is working not in objective measurements like pace and heart rate but in subjective factors. If, for example, a 9-minute mile feels easier today than it did a few weeks ago, your training is working. And if you feel less tired at the end of a 9-mile run than you did a few weeks ago, your training is also working.
My favorite subjective measure of training effectiveness, however, is the Hard Fun Test. If I could choose one test to determine whether an athlete I coached was making progress, I would gladly pass over all of the aforementioned physiological tests in favor of this qualitative self-assessment. Would you like to try to now? Here it is:
The Hard Fun Test
On a scale of 1 to 5, how accurate is the phrase “hard fun” in describing your current training experience?
- Perfectly accurate
- Very accurate
- Somewhat accurate
- Not very accurate
- Totally inaccurate
The correct answer—I mean, the ideal answer—is 1. The harder your training feels while remaining fun, and the funner your training feels is remaining hard, the more certain you can be that your training is working. Simply put, an endurance training program must be both hard and fun to be optimally effective, and if it is both hard and fun, there is nothing more that it should also be.
Feelings are not arbitrary. When your training feels hard, it does so for a reason. And when it’s fun, it’s fun for reasons that are highly relevant to your goals of getting fitter and performing better. In our techno-saturated modern existence, we tend to think of feelings as less reliable or valid than objective measurements, but where endurance training is concerned, the opposite is true.
Evidence that subjective assessments of training are more dependable than objective measurements comes from studies including one conducted by researchers at Ghent University and published in the International Journal of Sport Physiology and Performance in 2023. Eleven male cyclists completed five separate 3-kilometer time trials. The first time trial was done after a period of rest and served to establish a baseline. The other four time trials were done immediately after a separate workout, in a fatigued state. Naturally, a delta existed between the baseline time trial and the fatigued time trials, with all of the subjects producing less power in tired legs. This delta represented the actual impact of the prior workout on the cyclists.
What the researchers wanted to know was which method of quantifying training load (TL), or how hard a workout is, best predicted the delta between baseline time-trial performance and post-workout time-trial performance. Seven different methods were used to measure the training load of the workouts that preceded these time trials—six of them objective, based on heart rate and power data, and one subjective, based on rate of perceived exertion (RPE). Can you guess which method was most accurate in predicting the actual effect of these workouts on subsequent performance? Bingo!
“TL using the rating of perceived exertion was the only metric showing a response that was consistent with the acute performance decrements found for the different training sessions,” the study’s authors concluded.” In other words, simply asking the athlete how hard they felt the workout was resulted in not just the most accurate indication of how hard the workout really was but the only accurate indication of how hard the workout was.
One of the most fundamental principles of endurance training is progressive overload, which is based on the fact that, in order to increase fitness, an athlete’s current training load must be slightly greater than their recent training load. When an athlete is training in this way, they will perceive their training as hard, because again, feelings aren’t arbitrary. This perception is therefore a reliable indicator that the athlete is training appropriately—perhaps even the most reliable such indicator, as the Ghent study indicates.
Training musn’t be too hard, however, or the athlete will enter a state of nonfunctional overreaching, where the body is unable to absorb the work being done. And guess what: Decreased enjoyment of training is proven to be one of the best predictors and indicators of nonfunctional overreaching. And that is why training must be hard and fun in equal measure. The moment it becomes so hard that it’s no longer fun, it ceases to benefit the athlete.
French exercise physiologist Bertrand Baron coined the term affective load to refer to the emotional stress that corresponds to the physical stress imposed by training. Research on affective load shows a clear relationship between load patterns and performance. In general, athletes tend to improve most when the affective load hovers inside a sweet spot where they feel challenged but not overwhelmed by their training. Unlike most exercisers, athletes enjoy suffering in workouts, not because they enjoy suffering per se but because they find meaning in the specific form of suffering that makes them better at the sport they love. For this reason, a training program that is not hard enough (insufficient affective load) is just as bad as a training program that’s too hard (excessive affective load). Neither is terribly fun for the athlete who just wants to get better.
I would never advise a competitive endurance athlete to completely ignore their heart rate, power output, and other quantitative measures of fitness. These things are quite useful. But they’re not the key to endurance mastery, which is all about self-regulation, not data dependency. Getting the most out of your training requires that you know when it’s not yielding optimal results and make smart adjustments quickly when it isn’t. Paying attention to your affective load—either through the Hard Fun Test or informally—is a more effective way to keep your training on track and get it back on track when necessary than any objective measurement. It takes the responsibility away from technology and places it squarely on your shoulders, but like it or not, that’s the name of the game in endurance mastery.
To be clear, I’m not suggesting that training can or should be maximally hard and equally fun at all times. There are certain phases of training (the early base period, for example) that should not be very hard, and there are athletes who naturally find certain phases more fun than others. It’s easy, however, to account for these realities when self-administering the Hard Fun Test, asking yourself, in essence, “Does my training feel as hard as it should at this stage?” and also, “Am I having as much fun as I could at this stage of my training?” When the answer to either question is “no,” you have an opportunity to tweak your training to make it hard enough but not too hard or more fun at any given level of hardness—an opportunity you might not have had if you focused exclusively on numbers.