Human movement science
-
Human movement science · Apr 2014
Forward-backward postural protective stepping responses in young and elderly adults.
Protective steps are essential for fall avoidance. Most studies only examined forwards stepping despite considerable bio-mechanical and visual differences between the forwards and backwards directions. We assess forward-backward differences in protective steps in a young and elderly group. ⋯ Protective steps appear more robust than voluntary steps - they are earlier (shorter RT), longer and faster than voluntary steps, indicating an automatic rather than a volitional reaction. Backwards protective steps occur earlier than forwards; such promptness may have evolved out of bio-mechanical features which make falling backwards easier. Since our elderly subjects had an average age <70years, their slower and shorter protective backwards steps may represent the first abnormality in this rescue postural response. The findings in the elderly may partly depend on dysfunction in fronto-basal ganglia postural loops.
-
Human movement science · Feb 2014
Body size and countermovement depth confound relationship between muscle power output and jumping performance.
A number of studies based on maximum vertical jumps have presumed that the maximum jump height reveals the maximum power of lower limb muscles, as well as the tested muscle power output predicts the jumping performance. The objective of the study was to test the hypothesis that both the body size and countermovement depth confound the relationship between the muscle power output and performance of maximum vertical jumps. Sixty young and physically active males were tested on the maximum countermovement (CMJ) and squat jumps (SJ). ⋯ Both jumps revealed stronger relationships with Ppeak than with Pavg (p<.05) when controlled for either body mass or both body mass and countermovement depth. We conclude that both body size (in CMJ and SJ) and countermovement depth (in CMJ) confound the relationship between the muscle power output with the performance of maximum vertical jumps. Regarding routine assessments of muscle power from jumping performance and vice versa, the use of CMJ is recommended, while Ppeak, rather than Pavg, should be the variable of choice.
-
Human movement science · Dec 2013
Reorganised anticipatory postural adjustments due to experimental lower extremity muscle pain.
Automated movements adjusting postural control may be hampered during musculoskeletal pain leaving a risk of incomplete control of balance. This study investigated the effect of experimental muscle pain on anticipatory postural adjustments by reaction task movements. While standing, nine healthy males performed two reaction time tasks (shoulder flexion of dominant side and bilateral heel lift) before, during and after experimental muscle pain. ⋯ VM pain significantly reduced m. quadriceps femoris activity and TA pain significantly reduced ipsilateral VM activity and TA activity during bilateral heel lift. The EMG reaction time was delayed in bilateral soleus muscles during heels lift with VM and TA pain. The faster onset of postural muscle activity during anticipatory postural adjustments may suggest a compensatory function to maintain postural control whereas the reduced postural muscle activity during APAs may indicate a pain adaptation strategy to avoid secondary damage.
-
Human movement science · Oct 2013
Impaired visual perception of hurtful actions in patients with chronic low back pain.
Visually presented biological motion stimuli activate regions in the brain that are also related to musculo-skeletal pain. We therefore hypothesized that chronic pain impairs the perception of visually presented actions that involve body parts that hurt. In the first experiment, chronic back pain (CLBP) patients and healthy controls judged the lifted weight from point-light biological motion displays. ⋯ The second experiment involved discrimination between forward and backward walking. Here the patients were just as good as the controls, showing that the main result of the first experiment was indeed specific to the sensory aspects of the task, and not to general impairments or attentional deficits. The results thus indicate that the judgment of sensorimotor aspects of a visually displayed movement is specifically affected by chronic low back pain.
-
Human movement science · Oct 2013
Transversus abdominis is part of a global not local muscle synergy during arm movement.
The trunk muscle transversus abdominis (TrA) is thought to be controlled independently of the global trunk muscles. Methodological issues in the 1990s research such as unilateral electromyography and a limited range of arm movements justify a re-examination of this theory. The hypothesis tested is that TrA bilateral co-contraction is a typical muscle synergy during arm movement. ⋯ APA muscle activity of all muscles during asymmetrical arm movements typically reflected a direction specific diagonal pattern incorporating a twisting motion to transfer energy from the ground up. This finding is not consistent with the hypothesis that TrA plays a unique role providing bilateral, feedforward, multidirectional stiffening of the spine. This has significant implications to the theories underlying the role of TrA in back pain and in the training of isolated bilateral co-contraction of TrA in the prophylaxis of back pain.