EMG biofeedback: the effects of CRF, FR, VR, FI, and VI schedules of reinforcement on the acquisition and extinction of increases in forearm muscle tension

Effects of the Proprioceptive Neuromuscular Facilitation Contraction Sequence on Motor Skill Learning-Related Increases in the Maximal Rate of Wrist Flexion Torque Development

Background: The proprioceptive neuromuscular facilitation (PNF) reciprocal contraction pattern has the potential to increase the maximum rate of torque development. However, it is a more complex resistive exercise task and may interfere with improvements in the maximum rate of torque development due to motor skill learning, as observed for unidirectional contractions. The purpose of this study was to examine the cost-benefit of using the PNF exercise technique to increase the maximum rate of torque development.

Methods: Twenty-six participants completed isometric maximal extension-to-flexion (experimental PNF group) or flexion-only (control group) contractions at the wrist. Ten of the assigned contractions were performed on each of three sessions separated by 48-h for skill acquisition. Retention was assessed with 5 contractions performed 2-weeks after acquisition. Torque and surface electromyographic (sEMG) activity were analyzed for evidence of facilitated contractions between groups, as well as alterations in muscle coordination assessed across test sessions. The criterion measures were: mean maximal isometric wrist flexion toque; the maximal rate of torque development (dτ/dt_max); root-mean-square error (RMSE) variability of the rate of torque versus torque phase-plane; the rate of wrist flexion muscle activation (Q₃₀); a coactivation ratio for wrist flexor and extensor sEMG activity; and wrist flexor electromechanical delay (EMD).

Results: There were no significant differences between groups with respect to maximal wrist flexion torque, dτ/dt_max or RMSE variability of torque trajectories. Both groups exhibited a progressive increase in maximal strength (+23.35% p < 0.01, η² = 0.655) and in dτ/dt_max (+19.84% p = 0.08, η² = 0.150) from the start of acquisition to retention. RMSE was lowest after a 2-week rest interval (−18.2% p = 0.04, η² = 0.198). There were no significant differences between groups in the rate of muscle activation or the coactivation ratio. There was a reduction in coactivation that was retained after a 2-week rest interval (−32.60%, p = 0.02, η² = 0.266). Alternatively, EMD was significantly greater in the experimental group (Δ 77.43%, p < 0.01, η² = 0.809) across all sessions. However, both groups had a similar pattern of improvement to the third consecutive day of testing (−16.82%, p = 0.049, η² = 0.189), but returned close to baseline value after the 2-week rest interval.

Discussion: The wrist extension-to-flexion contraction pattern did not result in a greater maximal rate of torque development than simple contractions of the wrist flexors. There was no difference between groups with respect to motor skill learning. The main adaptation in neuromotor control was a decrease in coactivation, not the maximal rate of muscle activation.

Can doubt attenuate access to internal states? Implications for obsessive-compulsive disorder

BACKGROUND AND OBJECTIVES

We have previously reported that obsessive-compulsive individuals perform more poorly on tasks that require accurate perception of internal states. As these individuals are also characterized by elevated levels of doubt regarding internal states, the causal relationship between doubt and accurate perception remained unclear. The presented study examines whether undermining participants' confidence in their ability to accurately produce a specific internal state would affect their performance on a task that requires accurate perception of this state.

METHODS

Participants were trained to produce specific levels of forearm muscle tension and then required to produce various tension levels in four experimental phases. The first three alternated in terms of whether the participants viewed a biofeedback monitor while the fourth offered participants several times the choice to view the monitor. Prior to the task, half of the participants received instructions that undermined their confidence in their ability to accurately assess their own muscle tension. We measured participants' accuracy in producing the required muscle tension levels and the number of times they requested to view the monitor in the final phase.

RESULTS

Undermined confidence participants were less accurate in producing the required muscle tension levels in the absence of biofeedback, and were also more likely to request the monitor in the final phase.

CONCLUSIONS

Doubt can affect performance on tasks that require perceiving and experiencing internal states. This finding supports the possibility that access to internal states in OCD is attenuated due to elevated levels of doubt regarding these states.

Effects of ambulant myofeedback training and ergonomic counselling in female computer workers with work-related neck-shoulder complaints: a randomized controlled trial

OBJECTIVE

To investigate the effects of ambulant myofeedback training including ergonomic counselling (Mfb) and ergonomic counselling alone (EC), on work-related neck-shoulder pain and disability.

METHODS

Seventy-nine female computer workers reporting neck-shoulder complaints were randomly assigned to Mfb or EC and received four weeks of intervention. Pain intensity in neck, shoulders, and upper back, and pain disability, were measured at baseline, immediately after intervention, and at three and six months follow-up.

RESULTS

Pain intensity and disability had significantly decreased immediately after four weeks Mfb or EC, and the effects remained at follow up. No differences were observed between the Mfb and EC group for outcome and subjects in both intervention groups showed comparable chances for improvement in pain intensity and disability.

CONCLUSIONS

Pain intensity and disability significantly reduced after both interventions and this effect remained at follow-up. No differences were observed between the two intervention groups.

Functional MRI for neurofeedback: feasibility study on a hand motor task

We present an fMRI-based method that enables subjects to monitor and actively modulate their own brain activity as a form of biofeedback. On a 1.5 T clinical MR scanner, functional areas during a simple hand motor task were delineated by detecting signal variations associated with the brain activity. Then, the subject adopted a different strategy to expand the activation in motor and somatosensory areas that were not activated previously. Statistical maps of brain activity were visually presented back to the subject, being updated at the end of each segmented rest-task block in near real-time manner. Our results suggest that the visual feedback of the functional brain activation maps guided subjects to adjust their task performance to achieve the desired modulation of cortical activity. This method may offer a potential utility for fMRI-based neurofeedback.