Research Roundup: November 2020

 

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Locomotion and Dynamic Posture: Neuro-evolutionary Basis of Bipedal Gait

Guillaud E, et al. Locomotion and dynamic posture: neuro-evolutionary basis of bipedal gait. Neurophysiologie Clinique/Clinical Neurophysiology (2020),  https://doi.org/10.1016/j.neucli.2020.10.012

This review article explains the networks that the trunk in vertebrates with limbs, and also how the central nervous system acts dynamically on the musculoskeletal system.

 

Key Points
  • Dynamic control of gait is supported by:
    • Locomotor activity that is produced by specialized rhythmogenic spinal circuits called central pattern generators (CPGs), and which cyclically drive axial and leg muscle activity (p.8)
    • Posture control systems which involve long spinal/supraspinal loops, and the integration of various sensory inputs (e.g. proprioceptive, visual and vestibular) at various supraspinal levels resulting in long latency responses (p.8).

  • Dynamic balance in limbed vertebrates requires proper coordination of all segments of the body.
  • To maintain balance during movement, the internal forces generated by muscle movements interacts closely with the external forces (reaction forces and gravity).
  • The nervous system, skeletal tissue, and connective tissues are all required components for the dynamic state of organisms.

  • Connective tissues play an informative role in locomotion and posture.
  • Connective tissues support motor function by serving as “deformable skeletons.”
  • This ensures continuity between individual structures, which guarantees their stability while also conveying the mechanical tension that is generated by muscular activities.
  • Receptors embedded in connective tissues broadens the field of perception of changes, which triggers remote reflexes beyond the joint.

  • In bipedal gait, the axial motor command depends on projection-path coupling, as well as interactions between segmental spinal networks.
  • Motor pattern features of gait change depending on behavioural task requirements. 
  • During gait, a rostro-caudal propagation of biomechanical changes occurs along the spine.
  • As a person walks faster their trunk stiffens, and lateral flexion decreases during the gait cycle.
  • Studies suggest that back muscle vestibulospinal reflexes are relatively inflexible, while leg muscle responses are highly modulated.

 

Clinically: Teaching Pilates in Practice
  • Consider the rostro-caudal propagation of biomechanical spinal changes when cueing trunk and lower limb patterning exercises, especially those with reciprocal limb movements: Swimming; Prancing on the Wunda Chair or Reformer; Flutters on the Trapeze Table.  
  • Work to support trunk stiffness for reciprocal lower limb exercises, especially as the pace increases: side lying series can be a great position to work from; Bicycles on the Cadillac will give a greater challenge
  • Consider how this impacts the functional goal of the client you're working with: task requirements will impact the motor pattern that your client can access.

 

 

Sleep-dependent motor memory consolidation in healthy adults: a meta analysis

 Daniel Schmid, Daniel Erlacher, André Klostermann, Ralf Kredel, Ernst-Joachim Hossner. Sleep-dependent motor memory consolidation in healthy adults: A meta-analysis. Neuroscience & Biobehavioral Reviews, Volume 118, 2020. Pages 270-281. ISSN 0149-7634.

This meta-analysis compared the effect of sleep gain on motor memory consolidation between sleep and wake groups. The mechanisms by which sleep helps to consolidate motor memory are not fully understood, and further research is still needed in this field.

 

Key Points
  • Several studies show that whole-night and short diurnal sleep yield positive effects on motor tasks.
  • Longer periods of sleep are only show slightly improved effects over shorter "naps".
  • While positive, there is only a small effect of sleep on motor memory consolidation.

  • Physiologically, there are five stages of sleep (sleep stages 1-4 and rapid eye movement - REM - sleep).
    • During REM  sleep, biochemical processes in the central nervous system support the consolidation of new neuronal circuits.
  • Sleep spindle activity is believed to play a role in memory consolidation by facilitating neuronal plasticity.
  • There is  some evidence supporting the claim that implicit motor skills preferentially benefit from sleep, but other studies refute this.

     
Clinically: Teaching Pilates in Practice
  • Include a sleep hygiene assessment when working to facilitate changes in motor control.
  • Gauge your client's level of fatigue and tiredness during your session.
  • Encourage napping during the day - long enough to enter REM sleep - when working to consolidate motor learning.

 

 

Toe flexor strength is associated with mobility in older adults with pronated and supinated feet but not with neutral feet

Kusagawa, Y., Kurihara, T., Imai, A., Maeo, S., Sugiyama, T., Kanehisa, H., & Isaka, T. (2020). Toe flexor strength is associated with mobility in older adults with pronated and supinated feet but not with neutral feet. Journal of foot and ankle research13(1), 55. https://doi.org/10.1186/s13047-020-00422-y

This study sought elucidate the influence that foot posture has on the relationship between toe flexor strength and functional performance in older adults. The authors recognise the study's limitations: the study cohort was limited to women, and did not measure body kinematics or muscle activity.

 

Key Points
  • Both pronated and supinated foot postures influence rearfoot frontal plane motion, plantar pressure distribution, and muscle activity in the lower limb during gait.
  • Individuals with pronated feet require increased intrinsic muscle activity to stabilize the transverse tarsal joint, which enhances the generation of propulsive force.
  • Individuals with supinated feet have a decreased peak rearfoot eversion angle and midfoot eversion angle during gait.

  • Previous studies show that reduced toe flexor strength appears to be a risk factor for falls in older adults; toe flexor strength therefore determines mobility in older adults.
  • In older adults with pronated or supinated feet, toe flexor strength is significantly correlated with comfortable walking speed.
    • This is likely a compensatory strategy for altered lower limb biomechanics that occur as a result of foot pronation or supination.
    • Older adults with neutral feet do not exhibit a correlation between toe flexor strength and walking speed. 

 

Clinically: Pilates in Practice
  • Increased toe flexor strength is a compensatory strategy in older adults, and thus toe flexor strengthening without consideration of the underlying biomechanics changes at the foot may not be an optimal treatment goal.
  • If not already part of your studio repertoire, consider The Toe Gizmo or The Foot Corrector.
    • Both pieces of equipment can be easily replicated with bands and half-balls.   
  • In standing, ensure weight distribution over the tripod of the foot; Standing arm springs at the Tower; Standing Leg Press at the Wunda Chair.  
  • Build intrinsic foot muscle strength with the foot in as-close-as-possible to a neutral position; joint mobilisations and soft tissue techniques may be indicated.
  •  Reformer, Cadillac, and Wunda Chair footwork with neutral rearfoot and midfoot positioning.
  • Parakeet.
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