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Relationships between load, load capacity, performance and health are topics of contemporary interest. At what intensity should an athlete train to achieve the best physiological response? How much (or little) can an athlete train without detrimentally affecting health? Most studies addressing such questions have used a reductionist approach wherein factors were studied in isolation, thereby ignoring the complex inter-relationships and balance between factors. This editorial discusses the association between load and load capacity, and their relationship with athlete performance and health. We illustrate the practical use of a model for the management of athlete performance and health, and provide directions for future practice and research.
A balancing act
Figure 1 shows the intertwined relationships between load, load capacity, performance and health. To stimulate adaptation the basic principle of any training programme is to apply a load (ie, the amount of mechanical, physiological or mental stress) through training or competition that is greater than an athlete’s current load capacity (ie, the ability to tolerate load).1 With the optimal balance between both constructs, an appropriate training stimulus will elicit performance and health benefits.
In this relationship, an athlete’s load capacity will determine which load, in terms of volume, intensity and frequency, is beneficial. Equally, applying the correct amount of load will benefit the load capacity; for example, through an improvement in strength, (mental) resilience, bone mass, etc. However, one should keep in mind that an athlete’s load and load capacity, as well as the balance between both, are influenced by context and environment, both of which are temporal.2 3 This means that the balance between load and load capacity today may be tipped tomorrow due to fluctuations in fatigue, mental state, motivation, etc.
When load is off-balance with load capacity, there is heightened risk for detrimental health effects such as injury or illness. Such negative effects have been described after both overloading and underloading.4 5 Suboptimal health directly affects performance through reduced ability to perform (eg, through pain, restrictions, etc), but also indirectly through a reduced load capacity (eg, through reduced strength, stress, changes in tissue integrity). The latter, in turn, demands changes in the applied load to improve load capacity and manage the risk of further negative health changes.
Finding the balance in practice
The presented approach outlines that the modifiable factors of load and load capacity, and the outcomes of performance and health are interlinked. Any change in one component of the model affects others. Consequently, the various components must be considered together; adaptations in load alone will be insufficient to optimise performance while protecting athletes’ health. As an example, Møller et al 6 showed that handball players with reduced external rotational strength or scapular dyskinesis could withstand a lower increase in weekly handball load compared with players without such shoulder deficits. One could either adapt the load to the capacity of each player or improve the shoulder function of affected players, or preferably both. Another example is given by Malone et al 7 who described in Gaelic football players an increased injury risk related to high weekly workloads and acute:chronic workload ratios (>2.0). However, high aerobic capacity and greater playing experience moderated these effects and were protective for injury. The latter study illustrated the need to adapt training session content and intensity to the capacity of individual athletes, and the presence of modifiable load capacity factors which may vary during a season (eg, aerobic capacity).
Where to next?
In order to better understand the complex relationships between components and their strength and temporality, continuous and prospective monitoring is needed on each aspect. Such monitoring should not focus solely on objective physiological measures, but should also consider subjective (athlete reported) outcomes (eg, rate of perceived exertion (RPE)), psychological measures (eg, stress, coping mechanisms) and lifestyle-related factors such as diet, sleep, etc. This implies that many stakeholders within a sports context are involved in each of the model’s components and should register and access necessary parts of information. Such an integrated approach that holistically encapsulates various load, capacity, performance and health aspects is certainly not novel in the sports setting. However, little of the lessons learnt in sports practice trickle down to the peer-reviewed scientific literature. In addition, the available literature only paints a small part of the full picture by describing relationships in isolation without full consideration of contextual sports practice that needs to deal with the complex interactions as outlined in figure 1. We need to approach performance as the result of a complex interaction between a variety of temporal factors. Only then can we optimise the use of load and load capacity concepts in sports practice.
Contributors All authors contributed equally to the inception, thinking and writing for this editorial.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests TJG works as a consultant to several high performance organisations, including sporting teams, industry, military and higher education institutions. Both authors serve in a voluntary capacity as Senior Associate Editors of BJSM.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.