Abstract
Slips and stumbles are main causes of falls and result in serious injuries. Balance training is widely applied for preventing falls across the lifespan. Subdivided into two main intervention types, biomechanical characteristics differ amongst balance interventions tailored to counteract falls: conventional balance training (CBT) referring to a balance task with a static ledger pivoting around the ankle joint versus reactive balance training (RBT) using externally applied perturbations to deteriorate body equilibrium. This study aimed to evaluate the efficacy of reactive, slip-simulating RBT compared to CBT in regard to fall prevention and to detect neuromuscular and kinematic dependencies. In a randomized controlled trial, 38 participants were randomly allocated either to CBT or RBT. To simulate stumbling scenarios, postural responses were assessed to posterior translations in gait and stance perturbation before and after 4 weeks of training. Surface electromyography during short- (SLR), medium- (MLR), and long-latency response of shank and thigh muscles as well as ankle, knee, and hip joint kinematics (amplitudes and velocities) were recorded. Both training modalities revealed reduced angular velocity in the ankle joint (P < 0.05) accompanied by increased shank muscle activity in SLR (P < 0.05) during marching in place perturbation. During stance perturbation and marching in place perturbation, hip angular velocity was decreased after RBT (P from TTEST, Pt < 0.05) accompanied by enhanced thigh muscle activity (SLR, MLR) after both trainings (P < 0.05). Effect sizes were larger for the RBT-group during stance perturbation. Thus, both interventions revealed modified stabilization strategies for reactive balance recovery after surface translations. Characterized by enhanced reflex activity in the leg muscles antagonizing the surface translations, balance training is associated with improved neuromuscular timing and accuracy being relevant for postural control. This may result in more efficient segmental stabilization during fall risk situations, independent of the intervention modality. More pronounced modulations and higher effect sizes after RBT in stance perturbation point toward specificity of training adaptations, with an emphasis on the proximal body segment for RBT. Outcomes underline the benefits of balance training with a clear distinction between RBT and CBT being relevant for training application over the lifespan.
Highlights
Perturbation-related falls in response to slips or trips are major causes (>60%) of injuries over the lifespan (Gallagher et al, 1984; Winter, 1995; Rubenstein, 2006)
Comparing populations of high-risk fallers to non-fallers, beyond cognitive and strength deficits, factors as the following have been empirically identified as predisposing a person to a greater fall incidence: a decreased ability to stabilize postural equilibrium (Arampatzis et al, 2008), deteriorated balance recovery, undersized timing, and extent of the postural response (Tang and Woollacott, 1998)
For the reactive balance training (RBT)-group, reflexive biceps femoris (BF) muscle activity showed a tendency toward augmentation in SLR and long-latency responses (LLR) (Pt = 0.06)
Summary
Perturbation-related falls in response to slips or trips are major causes (>60%) of injuries over the lifespan (Gallagher et al, 1984; Winter, 1995; Rubenstein, 2006). Fall scenarios and related injuries among children (Gallagher et al, 1984), adults (Timsina et al, 2017), and seniors (Alexander et al, 1992) constitute a major public health problem and have gained socioeconomic importance due to high clinical and consequential costs (Miller et al, 2000; Stevens et al, 2006). Not the age itself, but rather the overall level of movement control seems to be the limiting factor to break one’s fall. This can be verified in both children who lack adult-like maturity of their joint control (Ganley and Powers, 2005) and in elderly who lose acquired skills as a result of progressive aginginduced degradation (Sawers et al, 2017). Independent of the age category, fall prevention programs have been established to counteract the falls and diminish consequential costs (Granacher et al, 2011a)
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