Fatigue-Related and Timescale-Dependent Changes in Individual Movement Patterns Identified Using Support Vector Machine.

The scientific and practical fields-especially high-performance sports-increasingly request a stronger focus be placed on individual athletes in human movement science research. Machine learning methods have shown efficacy in this context by identifying the unique movement patterns of individuals and distinguishing their intra-individual changes over time. The objective of this investigation is to analyze biomechanically described movement patterns during the fatigue-related accumulation process within a single training session of a high number of repeated executions of a ballistic sports movement-specifically, the frontal foot kick (mae-geri) in karate-in expert athletes. The two leading research questions presented for consideration are (1) Can characteristics of individual movement patterns be observed throughout the entire training session despite continuous changes, i.e., even as fatigue-related processes increase? and (2) How do intra-individual movement patterns change as fatigue-related processes increase throughout a training session? Sixteen expert karatekas performed 606 frontal foot kicks directed toward an imaginary target. The kicks were performed in nine sets at 80% (K-80) of the self-experienced maximal intensity. In addition, six kicks at maximal intensity (K-100) were performed after each of the nine sets. Between the sets, the participants took a 90-s break. Three-dimensional full-body kinematic data of all kicks were recorded with 10 infrared cameras. The normalized waveforms of nine upper- and lower-body joint angles were classified using a supervised machine learning method (support vector machine). The results of the classification revealed a disjunct distinction between the kinematic movement patterns of individual athletes. The identification of unique movement patterns of individual athletes was independent of the intensity and the degree of fatigue-related processes. In other words, even with the accumulation of fatigue-related processes, the unique movement patterns of an individual athlete can be clearly identified. During the training session, changes in intra-individual movement patterns could also be detected, indicating the occurrence of adaptations in individual movement patterns throughout the fatigue-related accumulation process. The results suggest that these adaptations can be modeled in terms of changes in patterns rather than increasing variance. Practical consequences are critically discussed.

Fatigue-related changes in technique emerge at different timescales during repetitive training.

Training consisting of numerous repetitions performed as closely as possible to ideal techniques is common in sports and every-day tasks. Little is known about fatigue-related technique changes that emerge at different timescales when repeating complex actions such as a karate front kick. Accordingly, 15 karatekas performed 600 kicks (1 pre-block and 9 blocks). The pre-block comprised 6 kicks (3 with each leg) at maximum intensity (K-100%). Each block comprised 60 kicks (10 with each leg) at 80% of their self-perceived maximum intensity (K-80%) plus 6 K-100%. In between blocks, the participants rested for 90 seconds. Right leg kinematics (peak joint angles, peak joint angular velocities, peak joint linear resultant velocities, and time of occurrence of peaks) and kick duration corresponding to the K-80% were measured resulting in numerous variations with fatigue. At the timescale of tens of seconds, the changes involved variables that were related to velocity of execution (slowed down), while variables related to movement form were hardly affected. At the timescale of tens of minutes, the opposite results were observed. These findings challenge the long-standing rationale underlying repetitive training, suggesting instead that such involuntary variations in technique might play a crucial role in motor skill training.

Different training programs decrease blood pressure during submaximal exercise.

OBJECTIVE: Our purpose was to study the effects of aerobic, resistance, and mixed (aerobic and resistance) training programs on blood pressure, both at rest and during submaximal exercise in healthy people. METHODS: We randomized 39 physically active, healthy participants into aerobic, resistance, and mixed (aerobic and resistance) exercise groups, and a control group. The exercise groups trained for 60 min three times/week for 6 weeks, and a submaximal cycle ergometer test was performed before and after training, and 3 weeks after detraining. Continuous blood pressure was determined before and during the test. RESULTS: At the submaximal test, both systolic and diastolic blood pressures decreased significantly (p < 0.05) after detraining in the exercise groups. However, between pre-training and detraining, we found significant reductions at rest only in the mixed exercise group (p < 0.05). CONCLUSION: Although all exercise had similar effects on blood pressure during submaximal exercise, the mixed aerobic and resistance exercise may be optimal for blood pressure reduction, by the addition of diverse physiological pathways.

Cardiorespiratory Coordination after Training and Detraining. A Principal Component Analysis Approach.

Our purpose was to study the effects of different training modalities and detraining on cardiorespiratory coordination (CRC). Thirty-two young males were randomly assigned to four training groups: aerobic (AT), resistance (RT), aerobic plus resistance (AT + RT), and control (C). They were assessed before training, after training (6 weeks) and after detraining (3 weeks) by means of a graded maximal test. A principal component (PC) analysis of selected cardiovascular and cardiorespiratory variables was performed to evaluate CRC. The first PC (PC1) coefficient of congruence in the three conditions (before training, after training and after detraining) was compared between groups. Two PCs were identified in 81% of participants before the training period. After this period the number of PCs and the projection of the selected variables onto them changed only in the groups subject to a training programme. The PC1 coefficient of congruence was significantly lower in the training groups compared with the C group [H (3, N=32) = 11.28; p = 0.01]. In conclusion, training produced changes in CRC, reflected by the change in the number of PCs and the congruence values of PC1. These changes may be more sensitive than the usually explored cardiorespiratory reserve, and they probably precede it.

Intentional thought dynamics during exercise performed until volitional exhaustion.

Using a non-linear approach, intentional dynamics of thoughts were examined during constant cycling performed until volitional exhaustion. Participants (n = 12) completed two sessions at 80% Wmax. Their (1) intrinsic thought dynamics (i.e., no-imposed thoughts condition) and (2) intentional thought dynamics (i.e., imposed task-unrelated thoughts condition; TUT) were recorded and then classified into four categories: internal and external TUT (TUT-I, TUT-E) and external and internal task-related thoughts (TRT-E, TRT-I). The probability estimates for maintaining each thought category stable, the rate of switching from one category to another, and the entropy dynamics along the testing procedure were assessed and compared through time phase. Friedman ANOVA tests revealed a significant effect of effort increase on thought contents only in the imposed TUT test. While TUT-I probabilities decreased significantly (P < .001) as effort increased, TRT-I probabilities increased (P < .05). Moreover, the entropy to the entire thought dynamics increased at the outset of task performance and decreased upon approaching volitional exhaustion (P < .001). As time spent in constant effort increased, and volitional exhaustion approached, task relatedness (TUT, TRT), direction (internal, external), and entropy of thought contents changed unintentionally providing further evidence for a nonlinear dynamics of attention focus.

El foco de atención emerge espontáneamente durante el ejercicio progresivo y máximo / Attention becomes spontaneously focused during progressive and maximum exercise / O Foco Atencional Emerge Espontaneamente Durante O Exercício Progressivo E Máximo

El objetivo de este estudio fue testar un modelo no lineal del foEl objetivo de este estudio fue testar un modelo no lineal del foco de atención imponiendo y sin imponer un pensamiento disociado durante un test cicloergométrico progresivo y máximo. Doce estudiantes previamente familiarizados con los procedimientos experimentales realizaron dos veces un test progresivo y máximo en cicloergómetro en dos condiciones diferentes: la primera, orientada a establecer su dinámica intrínseca, sin imponer ningún tipo de pensamiento, y la segunda imponiendo un pensamiento disociado (PD). Durante los test los participantes informaron cada 30s sobre su tipo de pensamiento (PD o PA -pensamiento asociado) a través de señales previamente convenidas. Las series individuales se dividieron en 10 intervalos temporales de intensidad creciente y se calcularon los porcentajes de PD y PA en cada una de ellas. Se encontraron porcentajes significativamente superiores de PA a partir del 6º intervalo de intensidad en el test con PD no impuesto (PDNI) (χ2 (12, 9) = 39.75; p < .001) y a partir del 8º intervalo en el test con PD impuesto (PDI) (χ2 (12, 9) = 70.65; p < .001). Los porcentajes de PD fueron superiores en el test PDI en 6 de los 10 intervalos de intensidad (p < .05). Los resultados demuestran la emergencia espontánea de PA durante el ejercicio progresivo y máximo confirmando el modelo no lineal del foco de atención

The objective of this study was to test a non-linear focus-of-attention model, with the imposition and non-imposition of dissociative thinking during a progressive and maximum bicycle ergometer test. Twelve students who were familiar with experimental procedures performed a progressive and maximum bicycle ergometer test twice under two different conditions: first so as to encourage the emergence of intrinsic dynamics, without imposing any type of thinking and, second, imposing dissociative thinking (DT). During the test, through previously agreed signals, the participants reported on their type of thinking every 30 seconds (DT or AT - dissociative or associative thinking). The individual series were divided into 10 temporary intervals of increasing intensity and the percentage of DT and AT in each one of them was calculated. The median percentage of AT was significantly higher from the 6th interval of intensity onwards in the non-imposed DT test (NIDT) (χ2 (12, 9) = 39.75; p < .001) and from the 8th interval onwards in the imposed DT test (IDT) (χ2 (12, 9) = 70.65; p < .001). The percentage of PD was higher in the PDI test in 6 of the 10 intervals of intensity (p < .05). The results demonstrate the spontaneous emergence of PA during a progressive and maximum cycling exercise, confirming the nonlinear focus-of-attention model

O objectivo deste estudo foi testar um modelo não linear do foco de atenção impondo e sem impor um pensamento dissociativo durante um teste cicloergométrico progressivo e máximo. Doze estudantes previamente familiarizados com os procedimentos experimentais realizaram duas vezes um teste progressivo e máximo num cicloergómetro em duas condições diferentes: a primeira, orientada para estabelecer a sua dinâmica intrínseca, sem impor nenhum tipo de pensamento, e a segunda impondo um pensamento dissociado (PD). Durante os testes os participantes informaram cada 30s sobre o seu tipo de pensamento (PD ou PA –pensamento associado) através de sinais previamente convencionados. As séries individuais dividiram-se em 10 intervalos temporais de intensidade crescente e foram calculadas as percentagens de PD e PA em cada uma delas. Verificaram-se percentagens significativamente superiores de PA a partir do 6º intervalo de intensidade no teste com PD não imposto (PDNI) (χ2 (12, 9) = 39.75; p < .001) e a partir do 8º intervalo no teste com PD imposto (PDI) (χ2 (12, 9) = 70.65; p < .001). As percentagens de PD foram superiores no teste de PDI em 6 dos 10 intervalos de intensidade (p < .05). Os resultados demonstram a emergência espontânea de PA durante o exercício progressivo e máximo, confirmando o modelo não linear do foco atencional

Rol de la intención en la terminación del ejercicio inducida por la fatiga. Aproximación no-lineal / A non-linear approach to the role of intention in fatiguing exercise

La intención tiene un papel reconocido en la terminación del ejercicio inducido por la fatiga pero se desconoce cómo interactúa con otros factores de origen fisiológico. El modelo de causalidad lineal, aplicado a las relaciones mente-cuerpo, no explica algunos de los fenómenos característicos relacionados con la terminación en tareas definidas por la intención motriz. El objetivo de este artículo de posicionamiento es investigar el papel de la intención en la terminación del ejercicio y revelar la integración psicobiológica no lineal que se produce durante el esfuerzo fatigante. En base a resultados experimentales se concluye que el mecanismo responsable de la terminación es la disolución del atractor intencional, provocada por la inestabilidad creciente que se desarrolla en el eje neuromuscular con la fatiga. Ello apunta hacia la existencia de una integración psicobiológica dinámica y no lineal en la fatiga inducida por el ejercicio (AU)

Intention has a well-recognised role in the termination point of fatigue-induced exercise; however its interaction with physiological factors is unknown. The linear causal model applied to mind-body relationships does not explain several characteristic phenomena related to the termination point in tasks defined by motor intention. This paper aims to investigate the role of intention in terminating exercise and reveal the non-linear psychobiological integration that occurs during fatiguing efforts. On the basis of the experimental results, we conclude that the mechanism responsible for termination is the dissolution of the intentional attractor that is produced by the growing instability that fatigue produces in the neuromuscular axis. These findings point to the existence of a non-linear, dynamic psychobiological integration in exercise-induced fatigue (AU)