Endurance training: the low-intensity paradox:

The concept of training intensity is critical for endurance athletes who want to maximize performance gains, and has been the topic of much debate among sport scientists. Once upon a time, a ‘no pain, no gain’ approach was common in athletes, where much of the training was conducted at hard or very hard intensity. In more recent years however, a growing body of evidence from elite athletes has accumulated that for maximum performance gains, there could be a better way. This better way revolves around a concept known as ‘polarized training’^(1-3). The polarized approach to training intensity proposes that endurance athletes spend a large proportion of their training time working at low intensity and a small proportion at a very high intensity, with relatively little time spent training at or near to lactate threshold.

The low-intensity focused approach

The theory behind a polarized approach is that it provides an excellent ‘aerobic foundation’ yet allows for high-intensity work that really stimulates training adaptation (ie aerobic fitness gains) without excessive fatigue. Studies show that high- or very high-intensity training is important for athletes to maximize performance^(4,5). However, it turns out that when looking at the training diaries of elite athletes who are training with a specific goal in mind, they almost universally prioritize the volume of low-, and not high-, intensity training in their programs. Indeed, when it comes to runners, it is large amounts of low-intensity training volumes compared to high intensity that appears to mark out the best performers (see figure 1)⁽⁶⁾. Indeed, elite athletes commonly devote the majority of their training time to the low-intensity zone, with isolated cases that may even exceed 90% of the total volume⁽⁷⁾.

Figure 1: Training intensity ratios and marathon finish time