A German reader asked me today how fast fitness is lost if you miss a day or, heaven forbid, several days of training. There are lots of confounding factors here but I’ll take a shot at it.
This is a particularly tender area for me right now as I am missing beaucoup workouts. While in Spain at a training camp two weeks ago I ran into a suddenly opened car door on a ride. It wasn’t a parked car, which I’m always pretty aware of, but rather a car stopped at a traffic light. A passenger decided to get out at mid-block and threw open the door just as I got there. Her timing was perfect. I landed on my hip which was fractured in four places. I’m now 17 days into no training.
So, never miss a workout… Obviously, that’s something which is nearly impossible to attain even if you haven’t broken your pelvis. Life sometimes just gets in the way. So let's take a look at missed workouts–or decreased training–from several varying perspectives.
Here’s what research on detraining by Randy Wilber at the Olympic Training Center in Colorado Springs, Colorado tells us about the changes that happen after three weeks of no training [Wilber]:
|
Effected Physiology |
Change |
|
Heart stroke volume |
-10% |
|
Heart rate at submax effort |
+4% |
|
Plasma volume |
-12% |
|
Capillary density |
-7% |
|
Aerobic enzymes |
-29% |
|
Blood lactate |
+88% |
|
Lactate threshold |
-7% |
|
Time to fatigue |
-10% |
|
VO2max |
-8% |
Anaerobic fitness, however, seems to hang on somewhat longer [Coyle]. So it’s aerobic function that we need to be most concerned about, especially since you are undoubtedly an endurance athlete given that you’re reading this blog. Even just reducing the number of aerobic workouts from 5 days per week to 2 causes a loss of significant amounts of fitness [Brynteson]. And reducing the intensity of your aerobic training below 70% of VO2max has been shown to also cause a loss of aerobic fitness with a decrease in aerobic capacity, time to exhaustion and heart size [Hickson].
There is also something relatively new, at least to endurance sport, referred to as “residual fitness” by Vladimir Issurin. This suggests that specific areas of fitness may be lost in a matter of a few days to a few weeks even if adequate training continues in some areas but with little or no specific stress in others [Issurin]. I’ll write more about this topic soon.
Using the WKO+ software model I can also tell you that if your fitness is relatively high you lose fitness at a much faster rate than if it is low. A single missed workout for someone with a CTL (Chronic Training Load) of about 100 TSS/day (high fitness) results in a fitness loss of more than 2%. But an athlete with a CTL of about 20 (low fitness) will see an approximate 0.4% drop in CTL when a day of training is missed. In other words, zeroes are more expensive when you’re highly fit.
So I guess my only hope is to lose a lot of fitness so my rate of fitness loss won’t be too great. That should be easy to pull off. But in the mean time I’m going to do what I can to exercise while I wait out this 6-week down time. I figure that even doing something is better than nothing—but probably more for my head than my body.
References
Coyle, E.F., W.H. Martin, D.R. Sinacore, et al. 1984. Time Course of Loss of Adaptations After Stopping Prolonged Intense Endurance Training. J Appl Physiol. 57:1857-1864.
Wilber, R.L. and R.J. Moffatt. 1994. Physiological and Biochemical Consequence of Detraining in Aerobically Trained Individuals. J Strength Cond Res. 8:110.
Brynteson P, W.E. Sinning. 1973. The Effects of Training Frequencies on the Retention of Cardiovascular Fitness. Med Sci Sports 5(1):29-33.
Hickson, R.C., C. Foster, M.L. Pollock, et al. 1985. Reduced Training Intensities and Loss of Aerobic Power, Endurance and Cardiac Growth. J Appl Physiol 58: 492-499.
Issurin, VB. 2009. Generalized training effects induced by athletic preparation. A review. J Sports Med Phys Fitness. 49(4):333-45.
