How to best address issues related to respondent fatigue or participant burnout?
Fatigue is a great problem. In colloquial language, the term “fatigue” is used to refer to the feeling of tiredness after an effort, which can be of a diverse nature and generates demotivation for the continuation of that effort, whether intellectual, work-related. or sporty. Unfortunately, there is no universally accepted definition of fatigue, which makes its nature conceptually complex and ambiguous.
Fatigue can be a consequence of physical or mental effort. This review will focus on fatigue as a state resulting from the practice of a physical-sports activity in which both types of effort are usually present and is associated with the training load (training stimulus that generates a breakdown of the body’s homeostasis). and causes the activation of allostatic mechanisms that allow the state of functional balance to be recovered).
The factors that contribute to fatigue resulting from physical activity arise not only from the physical effort, but also from the concomitant mental load and the results of the task being performed. Among the physiological factors that have been investigated in relation to fatigue, cardiovascular performance, muscular vascular occlusion, efficiency in the use of oxygen and nutrients, neuromuscular fatigue, and the presence of metabolites in the internal environment stand out.
Furthermore, factors directly implemented in the central nervous system (CNS) intervene in this process that serve to regulate effort and protect the body from damage that could occur due to overexertion.
However, fatigue also derives from the tactical nature of activity typical of motor interaction sports, in which the athlete invests an effort: on the one hand cognitive for decision making and on the other leading to emotional self-regulation. In this context, mental load, as an element that can influence fatigue, has become an area of research of undeniable importance. In this case, fatigue does not determine the inability to continue sporting activity, but rather to do so while maintaining an optimal level of performance.
Although experimentation on the factors that influence the appearance of fatigue points to multi-causal models, in the scientific literature there is an over-representation of physiological and biomechanical mechanisms, to the detriment of those from psychology or neuroscience, which is why An updated review of these aspects is very pertinent.
Concepts of fatigue and mechanisms that contribute to its appearance
The multicausal nature of fatigue has been the subject of study in biomechanics, physiology and psychology, the first 2 covering its objective nature and the latter its subjective and mental nature. This division of the study of fatigue has generated diverse and not always compatible definitions.
The physiological approach defines fatigue as a functional failure of the organism that is reflected in a decrease in performance and that generally originates from excessive energy expenditure or depletion of the elements necessary for its generation. In this sense, most research focuses on muscular aspects, understanding fatigue as a loss of the maximum capacity to generate force or a loss of power production.
However, the physiological explanation of fatigue goes beyond these aspects, making it necessary to also consider the effect that exercise produces on motor units, the internal environment and the CNS.
López-Chicharro and Fernández-Vaquero understand that fatigue can result from the alteration of any of the processes on which muscle contraction depends and appear as a consequence of the simultaneous alteration of several of these processes. This approach is also shared by authors such as Barbany, who distinguishes between fatigue resulting from a failure in central activation and peripheral fatigue.
The central and peripheral mechanisms have generally been studied in isolation, assuming that their combination occurs in a linear manner, which has probably produced biases in the interpretation of the data and in the conclusions obtained. Abbiss and Laursen have carried out a complete review of these models, which include: the cardiovascular/anaerobic model, the energy supply/depletion model, the neuromuscular model, the muscle trauma model, the biomechanical model, the thermoregulation model and, finally, the motivational/psychological model, which focuses on the influence of intrapsychological factors, such as performance expectations or required effort.
Cognitive strategies to manage fatigue
There are many athletes who use various cognitive strategies to influence their performance in competition, based on managing the discomfort caused by effort, delaying the onset of fatigue. Some research has used hypnotic suggestion to selectively modify the level of perceived exertion of participants, in order to identify the potential contributions of higher brain centers towards cardiorespiratory regulation and other peripheral physiological mechanisms. Some of them have shown that cognitive processes can exert a certain influence on the variations caused at a perceptual, and even metabolic, level through these hypnotic suggestions.
Different works analyze the relationship between perceived effort, cognitive processes and the effects they can have on resistance tasks, generating the development of cognitive strategies for their control. In general these have been included in 2 main types: associative and dissociative. With the former, the athlete concentrates on the signals he receives from the changes in his body state as a consequence of the effort made, while dissociative techniques are based on distracting the athlete with thoughts or mental tasks unrelated to the effort made. The distracting effect of these techniques is based on making use of attentional resources to leave the control of bodily sensations at an unconscious level.
Some of these works have focused their interest on verifying the degree of effectiveness of different cognitive processing strategies for sports performance. The first antecedents suggest that the level of sports performance could act as a mediator of the effectiveness of the different strategies, since the highest level athletes in long-term endurance tests tended to preferentially use associative strategies, while those of lower level level, the dissociative ones.
Probably the first work that attempted to verify this possible effect with an experimental design was that of González-Suárez. The results of the experiment revealed greater performance (longer endurance time) when the subjects ran to self-imposed exhaustion using associative strategies. Likewise, those with a higher athletic level kept running for longer than subjects with lower levels. Dissociative strategies also produced a decrease in perceptions of fatigue and physical exertion, while associative strategies tended to increase perceptions of fatigue.
On the other hand, Hutchinson and Tenenbaum conclude their work in a cycle ergometer resistance test at 50, 70 and 90% of VO2max< at i=2>, that “attentional focusing was predominantly dissociative during the low-intensity phase of the task, and turned toward predominantly associative as the intensity increased.” This seems to indicate that increasing the intensity of the exercise makes the subject unable to abstract from the bodily sensations generated by the exercise. In any case, as Díaz-Ocejo et al point out. , the results are currently not conclusive and it is advisable to approach the research considering other possible mediating variables of the effect of the different cognitive strategies.
Neurocognitive mechanisms of fatigue processing
The afferent information that can alter the RPE is very diverse, and it remains to be elucidated how the CNS integrates it and elaborates the sensation of fatigue. From some studies it is known that the nervous structures involved could be located in the insular cortex, the anterior cingulate cortex (medial prefrontal region) and the thalamic regions.
In relation to the distribution of training content
In the same way that the accumulation of physical load throughout training causes the appearance of fatigue and deterioration of performance, the accumulated effect of mental load contributes to the appearance of fatigue, and this to the decrease in physical performance. and engine.
For this reason, in training sessions in which the objective focuses on learning new game behaviors, motor responses of a high level of coordination, tactical aspects with high cognitive demands, or demands a high level of emotional self-control or concentration, the tasks that pursue it will be located in the initial part of the session, when the athlete has most of their physiological, cognitive and psychological resources available.
However, when the objective is not the acquisition of new motor schemes but the implementation of consolidated game actions and behaviors, the activities focused on their development will be located in the final phase of the training session, just when the accumulation of The physical and mental load leads to a state of fatigue that demands self-control from the athlete. That is, we would place the execution of those behaviors in training in the place that most closely simulates the situations in which those behaviors will have to be deployed in real competition.
If we focus the analysis on the distribution of content throughout a microcycle, for example, that of a team that competes during the weekend, the training activities that involve, on the one hand, greater physical effort and, on the other, greater Cognitive or emotional self-control should be located in the first part (Monday to Wednesday), reducing the magnitude of the loads in the days before competing to leave the necessary time to guarantee the recovery or supercompensation of the athlete.
In this sense, the evaluation of the athlete’s performance, or control of the training process, which is so advisable as a means to stimulate learning, must move away from competition, because as Buceta points out, it can generate stress that would add to what it already produces. the competition itself.