Why does age affect running speed?

In our previous article, we looked at how age affects running speed, now we turn to the why: what are the factors that affect our aerobic fitness and hence our endurance running performance?

Anyone who runs and is beyond a certain age will be very conscious of their decreasing running speed performance.
It is an ongoing battle to keep trying to post race times that we consider satisfactory. If a runner is to remain optimistic and motivated as the years advance they really have no choice but to accept a slowdown of some degree. We’ve mentioned that this slowdown is often less than commonly believed, but why does it occur at all?

Well, to answer this we need to look at the main factors that influence our endurance running potential, and these (according to Tanaka and Seals) are:

1. VO2max is the measure of the maximum amount of oxygen we can transport and use within the body. In short, it’s a measure of our aerobic energy production system and is often quoted as a level of fitness.
2. Lactate Threshold is the point at which during exercise blood lactate concentration rises significantly above baseline. Blood lactate levels rise when the body cannot remove the lactate as fast as it is producing it. This occurs when the anaerobic energy system has reached it’s maximum and the lactate system is significantly employed to meet the body’s energy requirements. As far as runners are concerned this will be at a pace slightly lower than 10k race pace. The lactate energy system is strictly limited and hence running above this level quickly becomes exhausting. Therefore, the lactate threshold will determine the pace a runner can maintain for longer periods.
3. Running Economy is not determined by VO2max, or lactate threshold. It is an efficiency measure of the oxygen we are consuming at a given sub-maximal pace. It is an important determinant of endurance running performance.
   The great thing about running economy and the aging runner is that numerous studies have shown that it is not affected by age. Unfortunately, that is not quite the case with the other two.

VO2max does deteriorate with age and because lactate threshold is dependent on VO2max, degradation is found here too. However it is not all bad news. Remove the VO2max effect on lactate threshold and age ceases to be a factor.
Of the 3 determinants of endurance running performance, VO2max suffers the most with advancing years. Various studies have shown that VO2max declines by about 10% per decade beyond 25-30 years. Thus, maximum oxygen update is the primary key in the reduction of running speed with age.

There is one other vital constituent in the reduction of the decrease in running speed and it might be the biggest factor of all. It might seem obvious, but it it very often overlooked; older runners, generally, do not train as hard or as much as younger athletes. There are of course some uncontrollable reasons for this. Sadly, the older runner is more injury prone. But against this are other things that we can control. Older runners, often due to family and other lifestyle reasons, have less time to train. Older runners also often suffer from decreased motivation, and this is a slippery slope:

low motivation = less training = poor performances = low motivation

Knowing this is immensely useful for athletes and coaches because it can help us adapt our training to keep us running faster for longer and with greater satisfaction and reward; we’ll look at how we do that in the next article. Clue: it’s not loads and loads of miles.