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Institute
Muscular fatigue can affect postural control processes by impacting on the neuromuscular and somatosensory system. It is assumed that this leads to an increased risk of injury, especially in sports such as alpine skiing that expose the body to strong and rapidly changing external forces. In this context, posture constraints and contraction-related muscular pressure may lead to muscular deoxygenation. This study investigates whether these constraints and pressure affect static and dynamic postural control. To simulate impaired blood flow in sports within a laboratory task, oxygen saturation was manipulated locally by using an inflatable cuff to induce blood flow restriction (BFR). Twenty-three subjects were asked to stand on a perturbatable platform used to assess postural-related movements. Using a 2 × 2 within-subject design, each participant performed postural control tasks both with and without BFR. BFR resulted in lower oxygenation of the m. quadriceps femoris (p = 0.024) and was associated with a significantly lower time to exhaustion (TTE) compared to the non-restricted condition [F(1,19) = 16.22, p < 0.001, ηp2 = 0.46]. Perturbation resulted in a significantly increased TTE [F(1,19) = 7.28, p = 0.014, ηp2 = 0.277]. There were no significant effects on static and dynamic postural control within the saturation conditions. The present data indicate that BFR conditions leads to deoxygenation and a reduced TTE. Postural control and the ability to regain stability after perturbation were not affected within this investigation.
Highlights
• Investigation of how the peripheral muscle system responds to imagination in interaction with proprioceptive information.
• Motor imagery altered time to contraction but not velocity and maximal displacement of the muscle belly.
• Findings indicate that MI might impact on the initiation of contraction.
Abstract
Many studies have investigated the activation of cortical areas and corticospinal excitability during motor imagery (MI) in relation to motor execution. Similar activation of cortical areas during imagined and executed bodily movements and increased corticospinal excitability while imagining movements has been demonstrated. Despite these similarities on the central nervous system level, there is no overt movement during MI. This suggests that centrally generated signals must be inhibited at some level. Second, even in the absence of movement, some studies find behavioral effects of MI interventions. Most of the studies have investigated the role of MI on the cortical or spinal level, but less is known about the peripheral level, such as the muscle system. Testing muscular excitability during MI will give further hints whether and how low-threshold motor commands during MI reach the muscular system. Furthermore, the extent of the shown effects during imagery depends considerably on type of imagery, available proprioceptive information, and imagery ability. Therefore, this study investigates muscular excitability of the biceps brachii muscle manipulating imagery mode (MI vs. visual imagery) and proprioceptive information (with or without muscle effort). 40 participants were included in the analysis. The mechanical response of the muscle after a single electrical stimulus was assessed via tensiomyography. The corresponding variables maximal displacement, delay time, and contraction velocity were used to calculate 2 × 2 ANOVAs with repeated measurements. The absence of interaction effects shows that possible imagery effects on the muscle system are not increased by effort. MI altered time to contraction with lower delay time compared to control condition. Velocity and maximal displacement of the muscle belly during contraction did not differ between imagery conditions. This indicates that MI might impact on the initiation of muscle contraction but does not change the contraction itself. Thus, neuronal factors are moving further into focus in the context of MI research.