The Path to Exhaustion: Time-Variability Properties of Coordinative Variables during Continuous Exercise

Abstract

The aim of this study was to detect qualitative changes in the structure of coordinative variable (elbow angle) fluctuations during a quasi-isometric exercise performed until exhaustion. Seven physical education students performed a quasi-isometric arm-curl exercise holding an Olympic bar (weight: 80% 1RM) with an initial elbow flexion of 90° three times over a period of 4 weeks. They were encouraged to persist, even if the elbow angle was lost, until the fatigue-induced spontaneous termination point (FISTP). Changes in both elbow angles were registered during the task through an electrogoniometer. Detrended Fluctuation Analysis (DFA) was conducted on the initial and final 1024 data points of the series and the associated Hurst exponents were obtained. Multi-way RM ANOVA analyses revealed a significant main effect of the Time on task on the Hurst exponent values but also revealed a significant Trial × Time on task interaction. In the initial (non-fatigue) condition participants tended to produce anti-persistent fBm fluctuations. In the final part before exhaustion a tendency toward persistent fBm was dominant. The trial to trial differences in time-variability structure points to an existence of a long-term variability in control strategies during exercise. The changes in the temporal structure of the elbow angle variability as effort accumulated reflected an increase in low-frequency fluctuations signifying a change in psychobiological mechanisms used to negotiate the task demands. The variability properties of the coordinative variable during exercise may provide information about the dynamic mechanisms that lead to exhaustion.

New approach for visualization of relationships between RR and JT intervals

“…This constant value of the load can be interpreted as a stable fixed point—which losses its stability due to the fatigue. Similar loss of stability in a quasi-isometric arm-curl exercise reflected by the increase of low-frequency fluctuations is observed in [25]. …”

Complex Systems in Sport, International Congress: Linking Theory and Practice

“…Discussion and conclusion: Implications of measuring team dynamics for understanding collective developmental systems in sports will be discussed with further analysis on our preliminary data sets. Introduction: Changes in the time-variability properties of a kinematic variable during a quasi-isometric exercise performed until exhaustion has been recently revealed (Vázquez et al, 2016). These changes, presumably informing about the state of the temporal couplings between the neuromuscular system's components, provided information about the dynamic mechanisms that lead to exhaustion.…”

From microscopic to macroscopic sports injuries. Applying the complex dynamic systems approach to sports medicine: a narrative review

“…The type of variability reflects the degree of coupling among the system components and its qualitative reorganisation. Vázquez et al 34 have shown that the change in the cooperative behaviour of neuromuscular components as fatigue develops is manifested through the changes in the time variability properties of the kinematic coordinative variable. A small perturbation (eg, pain sensation or imbalance) when the neuromuscular system is unstable, that is, close to exhaustion, can suddenly provoke the task disengagement.…”

“…Sports injuries arising after relatively long resting periods, such as those that occur during preseason, 60 may thus be explained by a mismatch between the performance that the athlete tries to achieve and his/her current capabilities. The lack of cooperation among biological levels reduces the synergistic possibilities of maintaining MSS stability 34 and should be carefully considered when designing training programmes. According to the antagonistic effects over different timescales pointed out here, it is likely not the increase or decrease of training workloads per se that affects MSS susceptibility to injuries, 54 but rather appropriate workload provided relative to timings.…”