The Impact of Detraining on Endurance Athletes: What Really Happens When You Take a Break

In all sports there is quite obviously, going to be a loss of form and performance when athletes take a break from training or practice. In endurance sports which don’t rely on years of developed skills to perform but instead rely heavily on physical condition, detraining is even more detrimental. A cricketer can spend a few weeks away from the game but can comfortably walk out onto the pitch and make a decent effort of batting because years and years of developing the hand/eye coordination and instincts will still come into play. Even if they might be a bit rusty at first. The same cannot be said for a cyclist, runner or triathlete. Endurance athletes need a period of preparation before toeing the line, no matter their years of experience.

As we come out of our Southern-hemisphere Winter and for many of us a period of winter hibernation, I thought it would be interesting to look at what actually happens in the body during a period of much lower or no endurance training and the physiological reasons behind our loss of form and fitness.

Our blood volume falls. As a result, there is a decrease in our cardiac output, or the amount of blood our hearts can pump per minute. The heart’s stroke volume, the amount of blood it can pump with every heartbeat during exercise is also reduced. The size of the heart muscle also decreases with inactivity. Respiratory function will decrease as well because of the weakening of the muscles in the ribcage. All of this reduces the amount of oxygen we can transport to our working muscles, which means our peak performance will decline.

Once we stop training, there is an increase in the ratio of carbohydrate to fats used as fuel during both maximal and submaximal exercise, with less energy derived from our fat stores. This will obviously decrease our endurance since carbohydrate stores are limited. Well-trained endurance athletes will utilise more energy from fat stores when exercising, even at relatively high exertion levels and this is virtually unlimited. In addition, less efficient oxygen metabolism means that, for a given effort level, higher levels of the fatigue causing blood-lactate accumulates in our muscles, making it harder for us to maintain the higher training intensities we were able to before detraining.

In the muscles that are our main drivers in either swimming, cycling or running, the density of capillaries, the tiny blood vessels that carry oxygen to muscles, decreases and the concentration of enzymes in muscle mitochondria used to release energy from oxygen, also decreases. Muscle fibres also shrink in cross section and the hormones involved with gaining or maintaining strength decline, quite clearly leading to strength and power losses.

Probably the most obvious result of a period of detraining is an increase in body weight. Some of that will be water, which we can shed in a few days of training but a drop in training volume doesn’t always coincide with a drop in appetite and, even the most disciplined amongst us will find it hard to reduce the caloric intake enough to offset the reduced amount of calories burned. 

Unfortunately, a holiday from a strict training routine generally means a relaxation in dietary control as well. We want to ‘let our hair down’ and eat the things that we may have been denying ourselves. So, there will definitely be an increase in body fat and resultant overall weight. The all-important power-to-weight ratio will be attacked from both sides during a period away from training as a result.

Maybe I should have written this before the Winter break because the good news is that only a fraction of the amount of training it took to get to a position of good form, is necessary to hold most of that. It is always much harder to get into good shape than it will be to maintain that. We are not professional athletes and we make sacrifices to train for the goals that we set ourselves. Once those targets are achieved, it is a natural thing to want to pack things in for a bit, live like our sedentary mates, chuck away the alarm clock etc. but, for most of us, endurance sport is a lifestyle, not a passing fad or checking an event off a ‘bucket list’. If you are a ‘lifer’ make things easier for yourself and keep things ticking during periods of unfocused training. It makes it a lot easier getting started again and also almost guarantees that you will reach a higher level at your peak in the following season.

Unless of course you enjoy the challenge of ‘starting from scratch’ again. That can also be its own kind of fun…