Test-retest Reliability Of Upper Limb Muscular Strength In Breast Cancer Survivors

Abstract

Upper limb muscular strength (ULMS) can be compromised by surgery in breast cancer survivors (BCS). Different physical and functional characteristics of upper limbs in BCS may interfere with strength measurements test-retest reliability. However, there is no data currently available on test-retest reliability of unilateral single or bilateral multi-joint strength measurements, such as handgrip strength (HGS) and bilateral isometric bench press test (BIBP), on the treated side of BCS when considering limb dominance. PURPOSE: To evaluate the test-retest reliability of ULMS in BCS who underwent surgery on the dominant treated side (onDS) or on the non-dominant treated side (nonDS). METHODS: Twenty-five BCS women (52.96 ± 8.77 years; 69.62 ± 14.97 kg) underwent ULMS assessments using HGS and BIBP in two days, three to seven days apart. The mean of three best attempts out of four to five were used for analyses. Test-retest reliability were analyzed using intraclass coefficient correlation (ICC) and coefficient of variation (CV). Paired samples t-tests were used to compare the results of the strength tests, test vs. retest. RESULTS: 40% of surgery was conducted in the nonDS (n=10) while 60.0% on the onDS (n=15). Test-retest reliability on onDS for the HGS and BIBP were ICC = 0.97 and CV = 2.78% and ICC = 0.87 and CV = 10.37% respectively. Test-retest reliability on nonDS for the HGS and BIBP were ICC = 0.91 and CV = 11.82% and ICC = 0.89 and CV = 7.52% respectively. Statistical difference was found between test-rest for HGS on nonDS (test = 21.47 ± 7.43 kgf, retest = 24.07 ± 5.57 kgf, p = 0.021), but not for HGS on onDS (test = 27.30 ± 4.63 kgf, retest = 27.42 ± 4.68 kgf, p = 0.754). For BIBP test, a significant difference between test-retest in the onDS (test = 97.65 ± 21.28 N, retest = 106.71 ± 27.44 N, p = 0.033), but not in the nonDS (test = 100.75 ± 22.12 N, retest = 104.65 ± 24.91 N, p = 0.435) was observed. CONCLUSIONS: Both, HGS and BIBP test are reliable measurements to assess ULMS in BCS; however, when surgery was on the nonDS, HGS may present higher within variability while when surgery was in the onDS, higher within variability was only observed for BIBP test. Further research is warranted to confirm or refute this initial study but also to identify specific factors that may have influenced the differences in HGS and BIBP measurements in the current study.