According to a cross-sectional study, the single-leg heel raise test (SLHRT) successfully differentiated between individuals with multiple sclerosis (MS) and healthy controls, with differences in the average number of heel raise repetitions (P <0.001) and in strength measurements (P =0.009) for the weaker leg.
Those with MS also had notable differences in the number of heel raise repetitions performed on the stronger limb, compared with the control group (P =0.001), but researchers did not observe differences in isometric strength between the groups.
In both groups, the SLHRT for the weaker limb correlated strongly with functional mobility measures including the timed 25-foot walk (T25FW) (r=0.71, P <.001), 2-minute walk test (2MWT) (r=0.73, P <.001), and functional stair test (FST) (−0.78, P <.001). The SLHRT for the stronger limb in both groups strongly correlated with the 2MWT (r=0.70, P <.001) and moderately correlated with the T25FW (r=0.62, P <.001) and FST (−0.62, P <.001) functional mobility assessments.
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These mobility activities require endurance during repeated muscular contractions instead of just one contraction, as is tested in isometric strength. Therefore, the SLHRT may more accurately reflect the endurance challenges accompanying mobility for those with MS.
Researchers observed that ankle plantarflexion strength in the weaker limb for the MS and control groups demonstrated moderate and significant correlations with the 2MWT (r=0.52, P =.003) and FST (−0.58, P =.001), respectively. However, in both groups, only a weak correlation between ankle plantarflexion strength in the weaker limb and T25FW (r=0.49, P =.005) existed. Investigators did not observe statistically significant associations in either group between ankle plantarflexion strength on the stronger limb and the T25FW (r=0.29, P =.117), 2MWT (r=0.31, P =.093), or FST (r=−0.34, P =.065).
The authors remarked that while the “single-leg heel raise test did not show strong convergent validity with electromechanical dynamometry…[it] was able to differentiate between people with MS and the [control] group for both weaker and stronger limbs.”
Consequently, the researchers explained the lack of a strong correlation between the SLHRT and dynamometry to be a result of the SLHRT testing endurance more than isometric strength. Therefore, they suggest that “clinicians may…consider using the single-leg heel raise test to identify people with MS who might benefit from improving ankle plantarflexion muscle performance as a means to improve mobility.”
Study Methods
The investigators enrolled 21 ambulatory individuals with MS and 10 individuals in an age- and sex-matched control group. They assessed ankle plantarflexion muscle performance using the SLHRT for endurance and the dynamometry for isometric strength. They collected functional mobility outcome measures using the T25FW, 2MWT, and FST. The participants performed each evaluation in a standardized order (T25FW, SLHRT, strength testing via dynamometry, FST, and 2MWT), with mandatory 5-minute rest breaks between each test.
Study Limitations
Limitations included the small sample size, floor effect of the SLHRT, possible impact of midfoot strength on the heel raise test outcomes, and lack of standardized “normal” values for the SLHRT in individuals with MS, which prompted the investigators to use the accepted cutoff of 20 heel raises to reflect “normal” strength measures. The researchers noted that this study had stronger than normal associations between functional mobility measures and muscle performance. They attributed this to the fact that they included the control group in their statistical analyses in addition to the MS group.
Reference
Mañago MM, Kline PW, Harris-Love MO, Christiansen CL. The validity of the single-leg heel raise test in people with multiple sclerosis: a cross-sectional study. Front Neurol. 2021;12:650297. doi:10.3389/fneur.2021.650297
