The single-leg heel test was able to differentiate between weaker and stronger limbs in patients with multiple sclerosis (MS) and in healthy controls, suggesting that the test could prove useful for identifying impaired muscle performance.
Although the single-leg heel test did not demonstrate strong convergent validity with electromechanical dynamometry, it was able to differentiate between weaker and stronger limbs in patients with multiple sclerosis (MS), according to a recent study.
The cross-sectional analysis, published in Frontiers of Neurology, showed that the single-heel leg test could be clinically useful for identifying impaired muscle performance in MS and differentiating muscle performance from healthy individuals.
“The single-leg heel raise test is a simple, clinically feasible muscle performance assessment that has previously been shown to be reliable in people with MS. The results from the current study support its validity for clinical evaluation and assessment of ankle plantarflexion muscle performance in people with MS,” wrote the investigators.
Impaired skeletal muscle performance is common among people with MS and ankle plantarflexion muscle performance is essential for mobility. However, measuring ankle plantarflexion can be costly, unavailable, and/or time-consuming, which can make detecting impaired muscle performance and assessing the impact of interventions challenging to accomplish.
Heel raise tests measure the total number of single-leg heel raises that a patient can do in a continuous bout at a consistent pace and research has demonstrated that these tests are reliable at assessing weaker and stronger limbs. The investigators said that their study is the first to compare the heel raise test with traditional testing for ankle plantarflexion strength, such as ankle plantarflexion isometric strength assessment using electromechanical dynamometry.
The investigators analyzed cross-sectional data from 21 (mean [SD] age, 49  years) people with MS and 10 (mean [SD] age, 48 ) age- and sex-comparable healthy people. The patients with MS had to be diagnosed by a neurologist and be able to ambulate 100 m without an assistive device. In addition to the heel raise test and electromechanical dynamometry, the participants performed the 2-minute walk test, and the timed 25-foot walk, and the functional stair test.
The single-leg raise test demonstrated weak convergent validity with ankle plantarflexion strength (r = 0.30; P = .020) across all limbs in the overall sample (n = 62). The heel raise test differentiated between groups on the MS groups’ stronger (P = .003) and weaker limbs (P < .001) when compared with the average control group values, whereas electromechanical dynamometry only differentiated between groups on the weaker limb (P = .010).
When analyzing the average values for the weaker and strong limbs, the investigators found that mobility measures had a moderate-to-strong correlations with the heel raise test on the weaker limbs for both groups (r = 0.71-0.78) and the stronger limbs for the MS group (r = 0.62-0.70). There was also a weak-to-moderate correlation with electromechanical dynamometry on the weaker limbs for both groups (r = 0.49-0.58; P = .001-.007).
Some of the limitations of the study listed were that not all participants with MS were able to complete any single-leg heel raises on the weaker limb, the heal raise test results may have been influenced by strength in the midfoot, and that there was a small sample size.
“While our findings should not be directly compared to prior work in MS, they do provide important information about the heel raise test and that it may be at least as good of an indicator of functional mobility as ankle plantarflexion strength measured by electromechanical dynamometry,” the investigators said.
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. Published online July 21, 2021. doi:10.3389/fneur.2021.650297