Humans plan for the near future to walk economically on uneven terrain

Humans experience small fluctuations in their gait when walking on uneven terrain. The fluctuations deviate from the steady, energy-minimizing pattern for level walking, and have no obvious organization. But humans often look ahead when they walk, and could potentially plan anticipatory fluctuations for the terrain. Such planning is only sensible if it serves some an objective purpose, such as maintaining constant speed or reducing energy expenditure, that is also attainable within finite planning capacity. Here we show that humans do plan and perform optimal control strategies on uneven terrain. Rather than maintain constant speed, they make purposeful, anticipatory speed adjustments that are consistent with minimizing energy expenditure. A simple optimal control model predicts economical speed fluctuations that agree well with experiments with humans (N = 12) walking on seven different terrain profiles (correlated with model r = 0.517 std. 0.109, P < 0.05 all terrains). Participants made repeatable speed fluctuations starting about seven to eight steps ahead of each terrain feature (up to 7.5 cm height difference each step, up to 16 consecutive features). They need not plan farther ahead, because each leg collision with ground dissipates energy, preventing momentum from persisting indefinitely. About seven to eight steps of continuous look-ahead and working memory thus suffice to practically optimize for any length of terrain. Humans reason about walking in the near future to plan complex optimal control sequences.Comment: 17 pages, 8 figure

Visual feedback-dependent modulation of arousal, postural control, and muscle stretch reflexes assessed in real and virtual environments

IntroductionThe mechanisms regulating neuromuscular control of standing balance can be influenced by visual sensory feedback and arousal. Virtual reality (VR) is a cutting-edge tool for probing the neural control of balance and its dependence on visual feedback, but whether VR induces neuromodulation akin to that seen in real environments (eyes open vs. closed or ground level vs. height platform) remains unclear.MethodsHere we monitored 20 healthy young adults (mean age 23.3 ± 3.2 years; 10 females) during four conditions of quiet standing. Two real world conditions (eyes open and eyes closed; REO and REC) preceded two eyes-open virtual ‘low’ (ground level; VRL) and ‘high’ (14 m height platform; VRH) conditions. We measured arousal via electrodermal activity and psychosocial questionnaires rating perceived fear and anxiety. We recorded surface electromyography over the right soleus, medial gastrocnemius, and tibialis anterior, and performed force plate posturography. As a proxy for modulations in neural control, we assessed lower limb reflexive muscle responses evoked by tendon vibration and electrical stimulation.ResultsPhysiological and perceptual indicators of fear and anxiety increased in the VRH condition. Background soleus muscle activation was not different across conditions; however, significant increases in muscle activity were observed for medial gastrocnemius and tibialis anterior in VRH relative to REO. The mean power frequency of postural sway also increased in the VRH condition relative to REO. Finally, with a fixed stimulus level across conditions, mechanically evoked reflexes remained constant, while H-reflex amplitudes decreased in strength within virtual reality.DiscussionNotably, H-reflexes were lower in the VRL condition than REO, suggesting that these ostensibly similar visual environments produce different states of reflexive balance control. In summary, we provide novel evidence that VR can be used to modulate upright postural control, but caution that standing balance in analogous real and virtual environments may involve different neural control states

Optimal regulation of bipedal walking speed despite an unexpected bump in the road.

Bipedal locomotion may occur over imperfect surfaces with bumps or other features that disrupt steady gait. An unexpected bump in the road is generally expected to slow down most types of locomotion. On wheels, speed may be regained quite readily with "cruise control" performed in continuous time. But legged locomotion is less straightforward, because the stance leg may be under-actuated, and the continuous-time dynamics are periodically disrupted by discrete ground contact events. Those events may also afford good control opportunities, albeit subject to the delay between discrete opportunities. The regulation of walking speed should ideally use these opportunities to compensate for lost time, and with good economy if possible. However, the appropriate control strategy is unknown. Here we present how to restore speed and make up for time lost going over a bump in the road, through discrete, once-per-step control. We use a simple dynamic walking model to determine the optimal sequence of control actions-pushing off from the leg at the end of each stance phase-for fast response or best economy. A two-step, deadbeat sequence is the fastest possible response, and reasonably economical. Slower responses over more steps are more economical overall, but a bigger difference is that they demand considerably less peak power. A simple, reactive control strategy can thus compensate for an unexpected bump, with explicit trade-offs in time and work. Control of legged locomotion is not as straightforward as with wheels, but discrete control actions also allow for effective and economical reactions to imperfect terrain

Lysozyme gene treatment in testosterone induced benign prostate hyperplasia rat model and comparasion of its’ effectiveness with botulinum toxin injection

ABSTRACT Objectives: To compare the effects and histopathological changes of botulinum neurotoxin type A and lysozyme gene injections into prostate tissue within a testosterone induced benign prostate hyperplasia rat model. Materials and Methods: 40 male Wistar rats were randomized into four Groups. Group-1: Control, Group-2: Testosterone replacement, Group-3: Testosterone+botulinum neurotoxin type A, Group-4: Testosterone+plazmid DNA/liposome complex. Results: Estimated prostate volume of the testosterone injected Groups were higher than the control (p <0.05). Actual prostate weight of the testosterone injected Groups was higher than the control Group (p <0.05). Testosterone undecanoate increased the prostate weight by 39%. Botulinum neurotoxin type A treatment led to an estimated prostate volume and actual prostate weights decreased up to 32.5% in rats leading to prostate apoptosis. Lysozyme gene treatment led to an estimated prostate volume and actual prostate weights decrease up to 38.7%. Conclusion: Lysozyme gene and botulinum neurotoxin type A treatments for prostate volume decreasing effect have been verified in the present study that could be anew modality of treatment in prostatic benign hyperplasia that needs to be verified in large randomized human experimental studies

Lysozyme gene treatment in testosterone induced benign prostate hyperplasia rat model and comparasion of its’ effectiveness with botulinum toxin injection

<div><p>ABSTRACT Objectives: To compare the effects and histopathological changes of botulinum neurotoxin type A and lysozyme gene injections into prostate tissue within a testosterone induced benign prostate hyperplasia rat model. Materials and Methods: 40 male Wistar rats were randomized into four Groups. Group-1: Control, Group-2: Testosterone replacement, Group-3: Testosterone+botulinum neurotoxin type A, Group-4: Testosterone+plazmid DNA/liposome complex. Results: Estimated prostate volume of the testosterone injected Groups were higher than the control (p <0.05). Actual prostate weight of the testosterone injected Groups was higher than the control Group (p <0.05). Testosterone undecanoate increased the prostate weight by 39%. Botulinum neurotoxin type A treatment led to an estimated prostate volume and actual prostate weights decreased up to 32.5% in rats leading to prostate apoptosis. Lysozyme gene treatment led to an estimated prostate volume and actual prostate weights decrease up to 38.7%. Conclusion: Lysozyme gene and botulinum neurotoxin type A treatments for prostate volume decreasing effect have been verified in the present study that could be anew modality of treatment in prostatic benign hyperplasia that needs to be verified in large randomized human experimental studies.</p></div