@article {4601,
	title = {Bidirectional locomotion induces asymmetric limb adaptations},
	journal = {Journal of neurophysiology},
	volume = {134},
	year = {2025},
	pages = {1774{\textendash}1784},
	abstract = {Humans can acquire and maintain motor skills throughout their lives through motor learning. Motor learning and skill acquisition are essential for rehabilitation after neurological disease or injury. Adaptation, the initial stage of motor learning, involves short-term changes in motor performance in response to a new demand in the person{\textquoteright}s environment. Repeated adaptation can improve skill performance and result in long-term skill retention. Locomotor adaptation has been extensively studied with split-belt treadmill paradigms. In this study we explored whether bidirectional walking (BDW) on a split-belt treadmill can induce short-term gait adaptations. Twelve healthy volunteers participated in our single session, starting with 2 min of forward walking (FW), followed by four 5-min blocks of BDW with a 1-min passive rest in between blocks, and ending with another 2-min block of FW. We recorded body kinematics and ground reaction forces throughout the experiment. Participants modified both temporal (interlimb phasing, double stance duration) and spatial (step length) aspects of gait to meet the mechanical demands of backward dual walking (BDW). Adaptation occurred rapidly, with bilateral reductions in step length, adjustments in stance and swing phase timing, alterations in interlimb phasing, and decreased double stance duration in the limb walking backward. Notably, only the backward-walking limb (right) exhibited persistent aftereffects upon return to FW. These results demonstrate that BDW elicits adaptations in both spatial and temporal gait parameters, with transient aftereffects consistent with short-term motor learning. To our knowledge, this is the first report characterizing such spatiotemporal adaptations during BDW.},
	author = {Hardesty, Russell L and Mojtabavi, Helia and Gemoets, Darren E and Wolpaw, Jonathan R}
}
@article {4606,
	title = {Soleus H-reflex size versus stimulation rate in the presence of background muscle activity: a methodological study},
	journal = {Experimental brain research},
	volume = {243},
	year = {2025},
	pages = {215},
	abstract = {Hoffmann reflex (HR) operant conditioning (HROC) is an important intervention for neurorehabilitation. Current HROC paradigms elicit HRs at low rates (~ 0.2 Hz), minimizing rate-dependent depression (RDD). We investigated the impact of higher stimulation rates on HR size. Fifteen healthy participants maintained low background soleus electromyographic activity (EMG) while standing. Soleus HR and M-wave recruitment curves were obtained at rates of 0.2, 1, and 2 Hz twice, from which Mmax and Hmax were calculated. Seventy-five HRs were collected for each rate at a target M-wave size (~ 10 to 20\% of Mmax). HR depression was minimal at higher stimulation rates. The mean HR amplitude was reliable across the two repetitions and three rates, with high intraclass correlation coefficient (ICC) values. HROC could be performed consistently at rates up to 2 Hz with minimal HR depression. Faster rates enable more conditioning trials per session, reducing session duration and/or number, thereby potentially accelerating conditioning and reducing participant burden.},
	author = {Brangaccio, Jodi A and Gupta, Disha and Mojtabavi, Helia and Hardesty, Russell L and Hill, NJ and Carp, Jonathan S and Gemoets, Darren E and Vaughan, Theresa M and Norton, James JS and Perez, Monica A and others}
}
@article {4600,
	title = {Spinal reflexes: a potential target for treating hemiparetic gait.},
	journal = {J Neurophysiol},
	volume = {134},
	year = {2025},
	month = {2025 Jul 01},
	pages = {290-291},
	issn = {1522-1598},
	doi = {10.1152/jn.00211.2025},
	author = {Hardesty, Russell L and Mojtabavi, Helia and Wolpaw, Jonathan R}
}
@article {4569,
	title = {Bidirectional locomotion induces unilateral limb adaptations.},
	journal = {bioRxiv},
	year = {2024},
	month = {2024 Aug 23},
	abstract = {<p>Humans can acquire and maintain motor skills throughout their lives through motor learning. Motor learning and skill acquisition are essential for rehabilitation following neurological disease or injury. Adaptation, the initial stage of motor learning, involves short-term changes in motor performance in response to a new demand in the person{\textquoteright}s environment. Repeated adaptation can improve skill performance and result in long-term skill retention. Locomotor adaptation is extensively studied using split-belt treadmill paradigms. In this study we explored whether bidirectional walking (BDW) on a split-belt treadmill can induce short-term gait adaptations. Twelve healthy volunteers participated in our single session, starting with 2 minutes of normal walking (NW), followed by four 5-minute blocks of BDW with a 1-minute passive rest in between blocks, and ending with another 2-minute of NW. We recorded body kinematics and ground reaction forces throughout the experiment. Participants quickly adapted to BDW with both legs showing decreased step lengths. However, only the backward-walking leg exhibited aftereffects upon returning to NW, indicating short-term adaptation. Notable kinematic changes were observed, particularly in hip extension and pelvis tilt, though these varied among participants. Our findings suggest that BDW induces unilateral adaptations despite bilateral changes in gait, offering new insights into locomotor control and spinal CPG organization.</p>},
	issn = {2692-8205},
	doi = {10.1101/2024.08.22.609228},
	author = {Hardesty, Russell L and Motjabavi, Helia and Gemoets, Darren E and Wolpaw, Jonathan R}
}
@article {4451,
	title = {The human motor cortex contributes to gravity compensation to maintain posture and during reaching.},
	journal = {J Neurophysiol},
	volume = {129},
	year = {2023},
	month = {01/2023},
	pages = {83-101},
	abstract = {<p>The neural control of posture and movement is interdependent. During voluntary movement, the neural motor command is executed by the motor cortex through the corticospinal tract and its collaterals and subcortical targets. Here we address the question of whether the control mechanism for the postural adjustments at nonmoving joints is also involved in overcoming gravity at the moving joints. We used single-pulse transcranial magnetic stimulation to measure the corticospinal excitability in humans during postural and reaching tasks. We hypothesized that the corticospinal excitability is proportional to background muscle activity and the gravity-related joint moments during both static postures and reaching movements. To test this hypothesis, we used visual targets in virtual reality to instruct five postures and three movements with or against gravity. We then measured the amplitude and gain of motor evoked potentials in multiple arm and hand muscles at several phases of the reaching motion and during static postures. The stimulation caused motor evoked potentials in all muscles that were proportional to the muscle activity. During both static postures and reaching movements, the muscle activity and the corticospinal contribution to these muscles changed in proportion with the postural moments needed to support the arm against gravity, supporting the hypothesis. Notably, these changes happened not only in antigravity muscles. Altogether, these results provide evidence that the changes in corticospinal excitability cause muscle cocontraction that modulates limb stiffness. This suggests that the motor cortex is involved in producing postural adjustments that support the arm against gravity during posture maintenance and reaching. Animal studies suggest that the corticospinal tract and its collaterals are crucial for producing postural adjustments that accompany movement in limbs other than the moving limb. Here we provide evidence for a similar control schema for both arm posture maintenance and gravity compensation during movement of the same limb. The observed interplay between the postural and movement control signals within the corticospinal tract may help explain the underlying neural motor deficits after stroke.</p>},
	keywords = {Electromyography, Evoked Potentials, Motor, Humans, Motor Cortex, Movement, Muscle, Skeletal, Posture, Pyramidal Tracts, Transcranial Magnetic Stimulation},
	issn = {1522-1598},
	doi = {10.1152/jn.00367.2021},
	author = {Hardesty, Russell L and Ellaway, Peter H and Gritsenko, Valeriya}
}
