Spinal and Supraspinal Motor Control Predictors of Rate of Torque Development

During explosive movements and potentially injurious situations, the ability to rapidly generate torque is critical. Previous research has suggested that different phases of rate of torque development (RTD) are differentiately controlled. However, the extent to which supraspinal and spinal mechanisms predict RTD at different time intervals is unknown. RTD of the plantarflexors across various phases of contraction (i.e., 0–25, 0–50, 0–100, 0–150, 0–200, and 0–250 ms) was measured in 37 participants. The following predictor variables were also measured: (a) gain of the resting soleus H-reflex recruitment curve; (b) gain of the resting homonymous post-activation depression recruitment curve; (c) gain of the GABAergic presynaptic inhibition recruitment curve; (d) the level of postsynaptic recurrent inhibition at rest; (e) level of supraspinal drive assessed by measuring V waves; and (f) the gain of the resting soleus M wave. Stepwise regression analyses were used to determine which variables significantly predicted allometrically scaled RTD. The analyses indicated that supraspinal drive was the dominant predictor of RTD across all phases. Additionally, recurrent inhibition predicted RTD in all of the time intervals except 0–150 ms. These results demonstrate the importance of supraspinal drive and recurrent inhibition to RTD

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 130, July 1974

This special bibliography lists 291 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1974

Neural contributions to maximal muscle performance

Neural activation is thought to be essential for the expression of maximal muscle performance, but the exact contribution of neural mechanisms such as the level of agonist, antagonist and stabiliser muscle activation to muscle strength is not fully understood. Explosive neuromuscular performance, including the ability to initiate (the electromechanical delay, EMD) and develop force rapidly (termed, rate of force development, RFD) are considered essential for the performance of explosive sporting tasks and joint stabilisation and thus injury avoidance. The thesis aimed to improve our understanding of the contribution of neural factors to muscle performance, with a specific focus on explosive neuromuscular performance. The work in this thesis utilised a range of approaches to achieve this aim. Initially, the association between muscle activation and rate of force development and EMD was established. Comparison of unilateral and bilateral actions was then undertaken. Finally interventions with the aim to both negatively affect and improve muscle strength, which included fatigue and resistance training (RT), respectively was undertaken and the neural contributions to changes in performance established. Agonist activation during the early phase of voluntary force production was shown to be an important determinant of voluntary EMD, explaining 41% of its inter-individual variability. Agonist activation was an important determinant of early, but not late phase RFD. Use of bilateral actions resulted in a reduction in explosive strength, which was thought to be due to differences in postural stability between unilateral and bilateral strength tasks. The level of stabiliser activation was strongly related to the level of agonist activation during the early phase of explosive force development and had a high association with explosive force production. Task-specific adaptations following isoinertial RT, specifically, the greater increase in isoinertial lifting strength than maximal isometric strength were due to training-specific changes in the level of agonist activation. High-intensity fatigue achieved a more substantial decline in explosive than maximal isometric strength, and this was postulated to be due to neural mechanisms, specifically decreased agonist activation. This work provides an in depth analysis of the neural contributions to maximal muscle performance

Aerospace medicine and biology. A continuing bibliography with indexes, supplement 186

This bibliography lists 159 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in October 1978

Evaluating Morphological Computation in Muscle and DC-motor Driven Models of Human Hopping

In the context of embodied artificial intelligence, morphological computation refers to processes which are conducted by the body (and environment) that otherwise would have to be performed by the brain. Exploiting environmental and morphological properties is an important feature of embodied systems. The main reason is that it allows to significantly reduce the controller complexity. An important aspect of morphological computation is that it cannot be assigned to an embodied system per se, but that it is, as we show, behavior- and state-dependent. In this work, we evaluate two different measures of morphological computation that can be applied in robotic systems and in computer simulations of biological movement. As an example, these measures were evaluated on muscle and DC-motor driven hopping models. We show that a state-dependent analysis of the hopping behaviors provides additional insights that cannot be gained from the averaged measures alone. This work includes algorithms and computer code for the measures.Comment: 10 pages, 4 figures, 1 table, 5 algorithm