What is fatigue? Seems obvious. When you’re tired after a bike ride.
Fatigability and Fatigue
Scientists are parsing this question. They distinguish between fatigability and fatigue. Fatigability is “an objective measurement of a person’s ability to do a physical or cognitive task — can be different from the perception of fatigue — a person’s subjective assessment of the fatigue they feel.”
Scientists had research subjects repeatedly squeeze a force transducer between their thumb and index finger. Once the force that they were exerting dropped by 40 percent of their baseline, they subjects stopped, and then they were asked how fatigued they felt.
Presumably the fatigability (level of muscular fatigue) is the same for everybody, but perceptions of fatigue varied.
Then the subjects completed a hand coordination task, which was not physically fatiguing, to test motor control relative to their perceived levels of fatigue.
The scientists expected those who felt more fatigued after the finger squeezing exercise would have poorer hand coordination. However, the reverse happened. People who reported less fatigue had less accurate coordination; those who said they felt more fatigue were more accurate.
The scientists suggest that “having more accurate motor control when feeling fatigued could indicate improved body awareness, which may, for example, help prevent someone from overdoing it physically and possibly getting injured.”
[Washington Post Rethinking fatigue: Feeling tired vs. being physically depleted.]
This theory fits with the central governor theory of fatigue. You have a subconscious system in your brain (central governor) that regulates how hard your muscles work so your speed / power never exceeds the capacity of your body to deal with the stress of exercise.
Sports scientists studied fatiguability in a stage race in the Alps by looking at data from start for each of the five stages each pro and each amateur. They examined the power profiles from start to finish of each pro and each amateur. There were no significant differences in the power profiles of the pro and U23 racers up to 30 minutes of racing except the U23s had a higher five-second power than the pros! The scientists then extended the analysis to two hours of racing. Not surprisingly the U23 racers’ power curves declined faster than the pros. The scientists then concluded that the best predictor of race performance wasn’t raw power or heart-rate. It was fatigue resistance.
Other sports scientists examined a group of elite runners training to break two hours in the marathon. They used three variables to predict a runner’s performance: 1) VO2 max, 2) running economy, and 3) what fraction of VO2 max a runner could sustain over the course of a marathon. Lactate threshold is often a proxy for the third variable. After studying the data the researchers suggested a fourth variable is also critical, which they called fatigue resistance, the extent to which the other three variables deteriorate during a race.
You can read more about both studies in my column on Anti-Aging: Fatigue Resistance Research.
In How Badly Do You Want It Matt Fitzgerald uses a number of excellent examples of endurance athletes and concludes the limit on performance is perceived exertion. If you perceive you’re going as long or hard as you can then you can’t do more.
Perceived exertion has two layers. The first layer is how your muscles feel. The second layer is how you feel about how your muscles feel. Your perception and assessment are largely based on your prior experience. Psychologists call this anticipatory regulation. Based on past rides you anticipate how far / fast you can go.
Fitzgerald provides examples of how changing perception results in higher performance,
You can read more in this column on Anti-Aging: Mastering Fatigue. Here’s practical example of how a rider changed his perceived exertion to master a long climb Anti-Aging: How Can an 83-Year-Old Climb Long Hills?
Fatigability and Learning a Physical Skill
In another experiment researchers divided participants into an experimental group and a control group. The experimental group did the same pinch test as above until performance declined by 40%. The control group didn’t do the exercise. Both groups then tried to learn a new physical skill. The fatigued group did poorly compared to the control group.
This makes sense. It’s harder to learn how to ride in a group if you’re very tired than if you’re fresh.
Interestingly, the experimental group’s ability to learn was also lower on the second day. It took two additional days of only moderate training to catch up to the learning ability of the control group.
“Thus, the common practice of training while, or beyond, fatigue levels should be carefully reconsidered, since this affects overall long-term skill learning.”
Intensity and Aging
Although not as fun as an endurance ride with your buddies, training hard has different benefits than endurance riding, important benefits as you age. Riding hard you mitigate and may even reverse muscle atrophy and not just in the fast-twitch muscle fibers in your legs. Your heart is a muscle, and as it ages the muscle fibers atrophy and your heart pumps less blood per beat. Your respiratory muscles also atrophy as you age. Your cardiac and respiratory muscles also lose elasticity. When you exercise hard, you increase the demands on your cardiac and respiratory muscles, which maintain more elasticity and fitness. You can read more in this column: Anti-Aging – Benefits of Training with Intensity
Several studies also suggest that including some type intensity can improve your lifespan. In a Norwegian study over five years, researchers found that the men and women who did twice a week intensity workouts were about two percent less likely to have died than participants who followed the standard recommendation: do 30 minutes of aerobic exercise most days of the week. The intensity doesn’t have to be flat out sprints. The high intensity participants cycled or jogged at 90% of max heart rate for four minutes, followed by four minutes of rest, with that sequence repeated four times. You can read more in this column: Anti-Aging: Interval Training Increases Longevity
Intensity, Aging and Learning a Physical Skills
Putting the above together, you need a couple of days of recovery after you do your intensity workout. However, these recovery days aren’t a good time to learn a cycling motor skill like better cornering.
My eBook Anti-Aging: 12 Ways You Can Slow the Aging Process has individual chapters on each of the types of exercise the American College of Sports Medicine recommends: cardiovascular both endurance and intensity; upper, lower, and core strength; weight-bearing, flexibility and balance. I include interviews with Gabe Mirkin (recommendations from an M.D.) Jim Langley (importance of goals), Andy Pruitt (importance of working on your skeleton, posture, balance, muscle mass), Muffy Ritz (recommended activities for older people, especially women), Malcolm Fraser (recommendations from an M.D.), Fred Matheny (importance of strength training), Elizabeth Wicks (motivation) and five other male and female riders ages 55 to 83. Anti-Aging: 12 Ways You Can Slow the Aging Process incorporates the latest research and most of it is new material not published in my previous eArticles on cycling past 50, 60 and beyond. It’s your comprehensive guide to continuing to ride well into your 80s and even your 90s. The 106-page eBook Anti-Aging: 12 Ways You Can Slow the Aging Process is available for $14.99.
Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written over 40 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John’s full bio.