Load-Induced Changes of Inter-Limb Asymmetries in Dynamic Postural Control in Healthy Subjects

Abstract

Inter-limb asymmetries are associated with a higher potential risk for non-contact injuries. Differences in function or performance between the limbs might lead to imbalances and promote instability, increasing the potential risk for injuries. Consequently, an investigation of inter-limb asymmetries should be included in injury risk assessment. Furthermore, since non-contact injuries mainly occur under loaded conditions, an investigation of load-induced changes of inter-limb asymmetries can provide additional information on the athlete’s potential injury risk. Therefore, the current study aimed to investigate the influence of physical load on inter-limb asymmetries in dynamic postural control, which is essential in situations with a high risk for non-contact injuries such as landing, cutting, or stopping. In total, dynamic postural control of 128 active and healthy subjects (64 males and 64 females, age: 23.64 ± 2.44, height: 176.54 ± 8.96 cm, weight: 68.85 ± 10.98 kg) was examined. Dynamic postural control was tested with the Y-Balance Test (YBT) before and after a loading protocol on a bicycle ergometer or a treadmill. The results showed no significant increase of the inter-limb asymmetries in anterior direction [F(1, 126) = 4.44, p = 0.04, η2p = 0.03]. Moreover, there is high variation between the subjects regarding the magnitude and the direction of the asymmetries and the changes due to load. Therefore, a more individual analysis considering the magnitude and the direction of the asymmetries is required. Thereby, considering different modifying factors, e.g., sex, injury history, and baseline level of asymmetries, can be helpful. Moreover, an analysis of the changes during load might provide further insights, reveal possible differences, and help detect the reasons and mechanisms underlying inter-limb asymmetries and asymmetrical loading.

Relationship between Asymmetries and Functional Autonomy in Older Chilean Adults

“…In this same analysis, it was observed that 39% of the evaluated older adults present asymmetries over 15% in the LL. In this sense, there is evidence that relates asymmetries between LL with a higher risk of injury [ 26 ] and risk of falling in older adults [ 29 ]. Likewise, although there is no scientific consensus to determine the percentage of asymmetry that generates a potential risk of suffering injuries or falls, it has been identified that an asymmetry ≥ 15% corresponds to an indicator of risk in healthy subjects [ 25 ].…”

“…Indeed, observing the dispersion of our results, it is evident that several older adults with levels of asymmetries place a population at risk (16 out of 41 older adults evaluated), especially for falling [ 29 ]. However, the evidence suggests that asymmetry analyses should be performed on a case-by-case basis and consider possible modifying factors [ 26 ].…”

“…Although there is no consensus or prospective cohort analysis to support the criterion, most of the available literature identifies that a difference in muscle strength or power ≥ 15% between limbs in healthy subjects generates an increased risk of injury [ 25 ]. Asymmetries must be assessed according to the nature of the movements [ 26 ]. For example, because movements of the upper limbs (UL) are typically performed unilaterally, strength assessments and, thus, determination of UL asymmetries in older adults should also be performed unilaterally; in this case, the most commonly used field test is the handgrip test [ 27 ].…”

“…In this case, the most used field test to evaluate the strength of LL in older adults is the Sit-to-Stand test [ 28 ]. These asymmetries can lead to body imbalances and instability, considerably increasing the risk of injuries [ 26 ] and falls in older adults [ 29 ]. Indeed, the study of asymmetries in humans has led to numerous investigations analyzing the differences between the LL and UL [ 23 , 24 ].…”