Isometric tests for the assessment of arm strength impairment in wheelchair rugby classification.

Introduction:

Valid impairment tests must be precise and reliable, ratio-scaled, quantitative, parsimonious, training resistant and specific to the impairment of interest. 

To infer strength impairment for the purpose of classification, isometric strength tests are favoured since they provide ratio-scaled, quantitative information about the maximum force generating capacities of muscle groups.

To ensure a battery of strength tests are specific for the measurement of arm strength impairment for WR, they should at least include an assessment of flexion and extension at both the shoulder and elbow, as these have been identified as key joint motions during wheelchair propulsion.

Study aims: 1) To explore a battery of isometric strength tests developed specifically for WR and to determine whether the tests could differentiate between (i) individuals with and without a strength impairment and (ii) male and female participants without a strength impairment. 2) To determine the test-retest reliability of the isometric strength tests in the unimpaired population.

Methods:

Twenty male WR athletes with impaired arm strength and thirty able-bodied (AB) participants (15 male, 15 female) performed four isometric strength tests. Each test required three 5-s efforts and examined maximal isometric force for flexion and extension around the shoulder and elbow joint.

Test validity was established by comparing differences (Cohen’s effect sizes [d]) in strength between WR athletes and AB participants. Differences were also explored between male and female AB participants.

Twenty AB participants returned for a second visit to establish the test-retest reliability of the test battery.

Main findings:

• Significantly lower force values were observed for all isometric strength measures in WR athletes compared to AB participants (p ≤ 0.0005; d ≥ 2.14).
• Female AB participants also produced significantly less force than male AB participants for all joint actions (p ≤ 0.0005; d ≥ 1.93).
• No significant differences were identified between trials for any measure of strength, with acceptable levels of test-retest reliability reported (ICCs ≥ 0.97, SEM ≤ 19.3 N and CV ≤ 8.4%).
• A battery of single-joint isometric strength tests was valid for the assessment of arm strength impairment in WR players and reliable amongst unimpaired participants.

Reference:

Mason BS, Altmann VC, Hutchinson MJ, Goosey-Tolfrey VL. Validity and reliability of isometric tests for the evidence-based assessment of arm strength impairment in wheelchair rugby classification. J Sci Med Sport. 2020 Jun;23(6):559-563. DOI: 10.1016/j.jsams.2019.12.022. Epub 2019 Dec 23. PMID: 31883779.