Motor patterns of patients with spinal muscular atrophy suggestive of sensory and corticospinal contributions to the development of locomotor muscle synergies.

Complex locomotor patterns are generated by combination of muscle synergies. How genetic processes, early sensorimotor experiences, and the developmental dynamics of neuronal circuits contribute to the expression of muscle synergies remains elusive. We shed light on the factors that influence development of muscle synergies by studying subjects with spinal muscular atrophy (SMA, types II/IIIa), a disorder associated with degeneration and deafferentation of motoneurons and possibly motor cortical and cerebellar abnormalities, from which the afflicted would have atypical sensorimotor histories around typical walking onset. Muscle synergies of children with SMA were identified from electromyographic signals recorded during active-assisted leg motions or walking, and compared with those of age-matched controls. We found that the earlier the SMA onset age, the more different the SMA synergies were from the normative. These alterations could not just be explained by the different degrees of uneven motoneuronal losses across muscles. The SMA-specific synergies had activations in muscles from multiple limb compartments, a finding reminiscent of the neonatal synergies of typically developing infants. Overall, while the synergies shared between SMA and control subjects may reflect components of a core modular infrastructure determined early in life, the SMA-specific synergies may be developmentally immature synergies that arise from inadequate activity-dependent interneuronal sculpting due to abnormal sensorimotor experience and other factors. Other mechanisms including SMA-induced intraspinal changes and altered cortical-spinal interactions may also contribute to synergy changes. Our interpretation highlights the roles of the sensory and descending systems to the typical and abnormal development of locomotor modules.NEW & NOTEWORTHY This is likely the first report of locomotor muscle synergies of children with spinal muscular atrophy (SMA), a subject group with atypical developmental sensorimotor experience. We found that the earlier the SMA onset age, the more the subjects' synergies deviated from those of age-matched controls. This result suggests contributions of the sensory/corticospinal activities to the typical expression of locomotor modules, and how their disruptions during a critical period of development may lead to abnormal motor modules.

Positive skill transfer in balance and speed control from balance bike to pedal bike in adults: A multiphase intervention study.

BACKGROUND: Learning to cycle can be challenging for adults who did not acquire the necessary skills during childhood. Balance bikes have been used to teach children how to cycle, but it was unclear whether this approach could also be effective for adults. PURPOSE: To address this, a multi-phase intervention study was conducted to investigate whether healthy adults could be taught to cycle independently through the use of a balance bike. METHODS: In Phase 1, a case-control observational study was conducted in which 13 cyclists and 8 non-cyclists completed balance bike tests. Based on the findings, an 8-session intervention pre- and post-test study was conducted in Phase 2, using an 8 × 20-minute balance bike training programme to improve cycling postural stability and control. Another 11 non-cyclists completed the novel programme. The time taken to complete the balance bike tests was compared before and after the program, while their cycling confidence was recorded in each session. To assess the effectiveness of the programme, participants were invited to cycle on a pedal bike to evaluate their ability to cycle independently. RESULTS: The results in Phase 1 showed that cyclists performed better on the balance bike than non-cyclists, with Bayes factor analyses providing evidence of this difference, BF01 = 0.228 in the 15 m sprint test and BF01 = 0.138 in the two-turn curved sprint test. The novel training programme in Phase 2 demonstrated remarkable effectiveness in improving their balance bike riding performance, as evidenced by the Bayes factor for completion times in the repeated measures being BF01 < 0.001. All participants were able to cycle independently with confidence after the programme. CONCLUSIONS: This study sheds light on the idea that it's never too late for adults to learn how to ride a bike. It provides evidence that healthy adults can learn to ride independently with the help of a balance bike, a tool that's commonly used for teaching children. The study identifies five key principles for effective balance bike training in adults, including focusing on riding speed, gliding to turn, building cycling confidence, engaging high motor skills, and using a dual-task approach. Our evidence-based training programme offers a safe, enjoyable, and effective way for adults to develop the skills and confidence they need to ride, even if they've never ridden before.