Role of Knee and Ankle Extensors’ Muscle-Tendon Properties in Dynamic Balance Recovery from a Simulated Slip

Abstract

Participants exposed to a simulated slip with forward loss of balance (FLB) develop large lower limb joint moments which may be a limiting factor for those whose muscle-tendon units’ (MTUs) properties are deteriorated. Whether the age-related decline in these properties limits participants’ capacity to recover their balance following a slip with FLB remains unclear. We combined isokinetic dynamometry, ultrasound and EMG to understand how knee extensor and ankle plantarflexor muscle strength and power, rate of moment development, electromechanical delay, and tendon stiffness affected the balance of young (25.3 ± 3.9 years) and older adults (62.8 ± 7.1 years) when recovering from a single slip with FLB triggered whilst walking on a split-belt instrumented treadmill. Except for the patellar tendon’s stiffness, knee extensor and ankle plantarflexor electromechanical delays, older adults’ MTUs properties were deteriorated compared to those of young participants (p < 0.05). We found no significant relationship between age or the MTUs properties of participants and balance recovery. These findings provide additional support that neither maximal nor explosive strength training are likely to be successful in preventing a fall for healthy older adults, and that other type of interventions, such as task-specific training that has already proved efficacious in reducing the risk of falling, should be developed.

The effects of plantarflexor weakness and reduced tendon stiffness with aging on gait stability

“…We may attribute our uncharacteristically strong older adults as a potential feature of their high physical activity levels documented using a standard health screening. Another explanation may be that normalized ankle torque values among our younger adults are low when compared with previously reported values [ 8 , 16 , 24 ], which could result from misalignment of ankle joint rotation axes with that of the dynamometer or insufficient recruitment of ankle musculature in younger adults. As we accounted for alignment of dynamometer and ankle joint axes of rotation in our setup [ 44 ] and gave consistent vocal encouragement for maximal effort to all participants [ 45 ], it is unclear why MVIC PF torque values among our younger adults were low in comparison with previous values.…”

“…Those authors found that, following unexpected treadmill belt accelerations perturbations, stronger older women had higher k AT and greater MoS Ant than weaker older women in subsequent recovery steps. By contrast, Debelle et al [ 8 ] found typical age-related differences in k AT but no age-related differences in MoS Ant during steady-state walking. Due to the nature of treadmill-induced slip perturbations, an anterior balance disturbance would intuitively require compensatory actions from the body in the sagittal plane.…”

“…Balance perturbations precipitating falls are most commonly experienced during walking, where mitigation of instability requires rapid repositioning of the base of support and sufficient ground reaction forces from the musculoskeletal system to arrest momentum. In younger adults, dynamic balance recovery following gait perturbations are partly dependent on large, rapid leg extensor moments [ 7 , 8 ]. With advanced age, adults experience sarcopenia [ 9 , 10 ] and decreased muscle strength [ 11 , 12 ], which would intuitively hinder balance recovery in older adults.…”

“…However, they later found increases in MTU capacity at the ankle through exercise had minimal effects on balance recovery in a similar population [ 26 ]. Most recently, Debelle et al [ 8 ] showed that age-related declines in MTU integrity were not related to balance recovery, as older and younger adults showed similar margins of stability in the anteroposterior (AP) direction. This finding is unusual, as older adults are often reported to be more unstable in the AP direction than younger adults immediately following AP balance perturbations [ 24 , 27 , 28 ], which the authors attribute to a comparatively young “older adult” sample.…”

Anterior Cruciate Ligament Rupture Combined with Complete Radial Tear of the Posterior Horn of the Lateral Meniscus: Suture or Resection?

“…46 Compared with patients who do not undergo ACL reconstruction, patients who undergo repair of a posterolateral meniscus root tear are at a lower risk of meniscus compression (in the sagittal plane) and OA. 47,48 Meniscal repair greatly helps with load distribution, joint stability, neuromuscular function, lubrication, and cartilage nutrition, 30,[49][50][51] and considering these benefits, these root tears should be repaired. Early maintenance may yield better results than delayed maintenance.…”