Background: Stability is one of the key demands in human locomotion including running. Various kinematical analytical approaches are adopted to investigate the running strategies; nevertheless, the impacts of running speeds on the variability of angles in individual lower limbs joints is still unclear. Objective: This study was aimed to investigate the impact of various running speeds on linear and non-linear variability of the hip, knee and ankle joints movement. Methods: Twenty-three collegiate athletes (13 females, 10 males, age 22.04 ± 3.43 years, body mass 62.14 ± 9.26 kg, height 168.29 ± 7.06 cm) ran at preferred running speed, 20% lower, and 20% higher than preferred running speed on a treadmill and their lower limbs joints kinematics were recorded using myoMOTION system at the sampling frequency of 200 Hz. The repeated measure analysis of variance test was adopted to investigate the linear (mean and standard deviation) and non-linear (Lyapunov exponent) variability of the hip, knee and ankle angle in sagittal, frontal and transverse planes throughout the running cycle. Results: No significant difference was observed between the lower limbs joint angles variability in linear analysis, while the Lyapunov exponent of the hip (p = .008, ηp2 = .338), knee (p = .002, ηp2 = .249) joints in the sagittal plane significantly increased as running speed increased. Conclusions: Findings of this study revealed that the hip and knee joints respond with more freedom of movement in the sagittal plane while walking speed increases, although nonlinear approaches were the only ones capable of detecting it. Given that speed changes might reduce body stability, it appears that these joints are attempting to maintain body stability by regulating internal body system perturbations by increasing their variability.
- Klíčová slova
- Lyapunův exponent,
- MeSH
- běh * fyziologie MeSH
- biomechanika MeSH
- lidé MeSH
- výzkum MeSH
- Check Tag
- lidé MeSH
Background: In contrast to strongly established views on the development of tonic, top-down controlled alertness, a small number of neurobehavioral and neurophysiological studies deal with the developmental trajectory of exogenously driven phasic alertness during childhood. Objective: The current study aimed to examine the age and sex effects on phasic alerting during late childhood, and to analyse the degree of association between tonic and phasic alertness at the behavioural level. Methods: Three age groups of typically developing children, aged 10, 11 and 12 years (N = 59, 27 boys, 32 girls) performed a computer-based simple hand-eye reaction test of alertness that involved 28 trials with and 28 trials without a warning signal. Results: The results showed a moderate decrease of mean reaction time in both the alert and non-alert conditions with age. However, the alert effect calculated as the difference in reaction times achieved in alert and non-alert conditions was not affected by age and sex. Conclusions: In contrast to previous suggestions on possible continuing improvement in phasic alertness during late childhood, the current study suggested that the neurocognitive function of transient enhancement in attentional alertness (phasic alertness) does not change and it is stabilized in this developmental period. In addition, this function does not differ between males and females in childhood.
