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]:
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%
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.
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
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.