Test-retest reliability and concurrent validity of knee extensor strength measured by a novel device incorporated into a weight stack machine vs. handheld and isokinetic dynamometry.

BACKGROUND: The current clinical gold standard for assessing isometric quadriceps muscle strength is an isokinetic dynamometer (IKD). However, in clinics without an IKD, clinicians default to using handheld dynamometers (HHD), which are less reliable and accurate than the IKD, particularly for large muscle groups. A novel device (ND) was developed that locks the weight stack of weight machines, and measures forces applied to the machine, turning this equipment into an isometric dynamometer. The objectives of this study were to characterize the test-retest reliability of the ND, determine the within-day and between-days inter-rater reliability and concurrent validity compared with that of the HHD, in healthy volunteers (HV) and individuals with knee osteoarthritis (OA) for measuring knee extensors isometric muscle force. MATERIALS AND METHODS: 29 healthy (age = 28.4 ± 7.4 years) and 15 knee OA (age = 37.6 ± 13.4 years) participants completed three maximum force isometric strength testing trials on dominant side knee extensor muscles on three devices (ND, HHD, and IKD) in two separate sessions by two raters. The maximum force (Fmax) produced, and the force-time series were recorded. Reliability and validity were assessed using Intraclass Correlation Coefficient (ICC), Bland-Altman Plots, Pearson's r, and cross-correlations. RESULTS: The ND demonstrated excellent test-retest reliability (ICC2,3 = 0.97). The within-day (ICC2,3 = 0.88) and between-day inter-rater reliability (ICC2,3 = 0.87) was good for HHD. The ND showed excellent within-day (ICC2,3 = 0.93) and good between-day (ICC2,3 = 0.89) inter-rater reliability. The Bland-Altman analysis revealed HHD systematic bias and underestimation of force particularly with quadriceps force values exceeding 450 N. Mean differences were found in maximum force between HHD vs. IKD (MDabs = 58 N, p < .001) but not the HHD vs. ND (MDabs = 24 N, p = .267) or ND vs. IKD (MDabs = 34 N, p = .051). The concurrent validity of Fmax (r = 0.81) and force-time curve correlation (0.96 ± 0.05) were the highest between the ND and IKD. CONCLUSIONS: The ND's test-retest reliability and concurrent validity make it a potential strength assessment tool with utility in physical therapy and fitness settings for large muscle groups such as the knee extensors.

Pectoralis minor muscle elongation and scapulothoracic motion do not differ in individuals with short versus typical resting pectoralis minor muscle length: a cross-sectional study.

BACKGROUND: Individuals with short resting pectoralis minor muscle length have been shown to have aberrant scapulothoracic motion when compared to individuals with long resting pectoralis minor muscle length. However, the degree to which the pectoralis minor muscle can be lengthened and whether or not scapulothoracic motion differs between individuals with short and typical resting pectoralis minor muscle length is unknown. OBJECTIVES: To determine if: (1) pectoralis minor muscle elongation (percent pectoralis minor muscle can be actively and passively lengthened beyond resting length), (2) pectoralis minor muscle percent length change during overhead reaching, and (3) scapulothoracic motion during overhead reaching differ between individuals with short and typical resting pectoralis minor muscle length. DESIGN: Two group comparison. METHODS: Thirty healthy individuals were placed into a short or typical resting pectoralis minor muscle length group. A caliper was used to measure resting pectoralis minor muscle length and pectoralis minor muscle length during active and passive muscle lengthening. An electromagnetic tracking system was used to measure pectoralis minor muscle length change as well as scapular, humeral, and trunk motion during several arm elevation tasks. Pectoralis minor muscle elongation and length change during arm elevation tasks were compared between groups using independent t-tests. Two-factor mixed-model analyses of variance were used to compare scapulothoracic motion at arm elevation angles of 30°, 60°, 90°, and 120°. RESULTS: Pectoralis minor muscle elongation and pectoralis minor muscle length change during arm elevation did not differ between groups. Scapulothoracic motion did not differ between groups across arm elevation tasks. CONCLUSIONS: Although resting pectoralis minor muscle length differed between groups, pectoralis minor muscle lengthening and scapulothoracic motion were similar between participants with short and typical resting pectoralis minor muscle length. Additional studies are needed to better understand the role of pectoralis minor muscle elongation on scapulothoracic motion.

Reliability and validity of active and passive pectoralis minor muscle length measures.

BACKGROUND: Pectoralis minor muscle length is believed to play an important role in shoulder pain and dysfunction. Current clinical procedures for assessing pectoralis minor muscle length may not provide the most useful information for clinical decision making. OBJECTIVE: To establish the reliability and construct validity of a novel technique to measure pectoralis minor muscle length under actively and passively lengthened conditions. DESIGN: Cross-sectional repeated measures. METHODS: Thirty-four healthy adults (age: 23.9, SD=1.6 years; 18 females) participated in this study. Pectoralis minor muscle length was measured on the dominant arm in three length conditions: resting, actively lengthened, and passively lengthened. Based upon availability, two raters, out of a pool of five, used a caliper to measure the distance between the coracoid process and the 4th rib. The average of two pectoralis minor muscle length measures was used for all muscle length conditions and analyses. Intraclass correlation coefficients determined intra-and inter-rater reliability, and measurement error was determined via standard error of measurement and minimal detectable change. Construct validity was assessed by ANOVA to determine differences in muscle length across the three conditions. RESULTS: Our intra- and inter-rater reliability values across all three conditions ranged from 0.84 to 0.92 and from 0.80 to 0.90, respectively. Significant differences (p<0.001) in muscle length were found among all three conditions: rest-active (3.66; SD=1.36cm), rest-passive (4.72, SD=1.41cm), and active-passive (1.06, SD=0.47cm). CONCLUSIONS: The techniques described in this study for measuring pectoralis minor muscle length under resting and actively and passively lengthened conditions have acceptable reliability for clinical decision making.

Functional testing to determine readiness to discontinue brace use, one year after acl reconstruction.

BACKGROUND: While the use of functional knee braces for return to sports or high level physical activity after ACL reconstruction (ACLR) is controversial, brace use is still prevalent.(1,2,3,4,5) All active patients in the practice are braced after ACLR and must pass a battery of sports tests before they return to play in their brace. Criteria include a 90% score on 4 one-legged hop tests(9) burst superimposition strength test,(10) Knee Outcome Survey Activities of Daily Living Scale,(8) and a global rating of knee function. PURPOSE: The purpose of this study was to describe the use of criterion-based guidelines to determine if athletes who had undergone an ACLR function better with or without their functional brace, one year after surgery. STUDY DESIGN: Cross-Sectional Study. METHODS: Sixty-four patients post ACLR performed 4 one-legged hop tests,(9) burst superimposition strength test,(10) and completed the Knee Outcome Survey Activities of Daily Living Scale,(8) and a global rating of knee function one year after surgery with and without their brace. RESULTS: Participants included 35 men and 29 women with a mean age of 25 years. The Mean Knee Outcome Survey Activities of Daily Living score was 98%, and the global rating was 97%. Of the subjects, one patient failed hop testing by at least one criterion with and without the brace. Three additional patients failed the test while braced but passed un-braced, and one patient passed with the brace, but failed without the brace. Subjects performed significantly better un-braced than braced in all hop tests: single leg hop braced = 101%; un-braced = 107% (p<0.001); cross-over hop braced = 100%; un-braced = 105% (p<0.001); triple hop braced = 99%; un-braced = 101% (p=0.003); timed hop braced = 98%; un-braced = 103% (p = 0.004). CONCLUSIONS: Sixty-two of 64 patients continued to score above return to play criteria one year after ACLR. All but two subjects in the cohort performed better un-braced than braced. Based on the criterion set for this testing session, 62/64 individuals performed well enough to discontinue use of their brace. LEVEL OF EVIDENCE: 2b.