Can You Trust Your Strength Assessment? Evaluating the Reliability and Validity of Handheld and Externally Fixated Dynamometers for Measuring Knee and Hip Strength.

Due to cost barriers and/or space constraints, electromechanical and hand-held dynamometry are underutilized in rehabilitation settings. As a result, clinicians often rely on semi-quantitative methods that may fail to detect deficits in upper or lower extremity strength. The purpose of this study was to examine the between-trials test-retest reliability and concurrent criterion validity of an accessible crane scale for measuring isometric knee and shoulder strength. Observational cohort, Cross-sectional study. Twenty healthy, recreationally active adults underwent isometric knee and shoulder strength testing using a crane scale, electromechanical dynamometer, and hand-held dynamometer during a single session. Knee extension and flexion, and shoulder internal rotation, external rotation, and abduction were tested. Three maximal effort trials were performed per device and motion, with the order of device testing randomized. Between-trials test-retest reliability of the crane scale was assessed using intraclass correlation coefficients (ICCs). Concurrent criterion validity was examined using ICCs, absolute and relative error, Bland-Altman plots, and simple linear regression. Test-retest reliability of the crane scale was excellent for all motions (ICCs ≥ 0.90). Concurrent validity was poor to moderate with the electromechanical dynamometer (ICCs = 0.36-0.72) but excellent with the hand-held dynamometer (ICCs ≥ 0.90). There was a negative bias for the crane scale compared to alternative devices and evidence of a proportional bias for knee extension and shoulder abduction. A crane scale provides values similar to hand-held dynamometry but is not comparable to results from electromechanical dynamometry. The lack of concurrent validity between the crane scale and electromechanical dynamometry may be partially attributable to differences in stabilization and participant positioning. 3b, reliablity and validity study.

Hand-held dynamometers (HHDs) are widely used to measure isometric muscle force in clinical practice. However, reliability may be affected when there is a difference in muscle force generation between examiner and patient, raising concerns about accuracy in physically trained populations, such as military personnel. This study aimed to examine the inter-rater and intrarater reliability of HHD for lower limb strength assessment in a healthy military population. Secondary aims were to evaluate the validity of HHD for knee extensor strength compared with fixed dynamometry and explore the impact of assessor and participant characteristics on reliability. A cross-sectional study with test-retest reliability and concurrent validity design was conducted with 30 healthy military personnel (mean age: 32±6 years; 24 males; 6 females). Peak isometric lower limb force was measured across six positions using HHDs (Lafayette, USA) by three assessors across two sessions. Knee extensor strength was also assessed using an isokinetic dynamometer (Biodex, USA). Intrarater and inter-rater relative reliability were assessed using intraclass correlation coefficients (ICC), and absolute reliability with SEM and minimal detectable change (MDC). Concurrent validity was determined using Pearson's correlation, and systematic bias was analysed through limits of agreement. Intra-rater reliability was good-to-excellent (ICC>0.75; SEM% 2.1%-6.3%; MDC% 5.2%-17.6%) across all positions except one assessor in hip extension (ICC=0.70). Inter-rater reliability was also good-to-excellent (ICC>0.75; SEM% 2.2%-5.5%; MDC% 6.1%-15.4%). HHD demonstrated strong validity compared with isokinetic dynamometry (r=0.80-0.819, p<0.001) despite a systematic bias with lower values. No correlation was found between peak force and inter-rater variability. HHD is a reliable tool for lower limb strength assessment in military personnel. Although absolute values are lower than fixed dynamometry, relative comparisons over time remain valid.

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. 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. 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. 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.

Measuring isometric shoulder rotational strength is clinically important for evaluating motor disability in athletes with shoulder injuries. Recent evidence suggests that handheld dynamometry may provide a low-cost and portable method for the clinical assessment of isometric shoulder strength. To investigate the concurrent validity and the intrarater and interrater reliability of handheld dynamometry for measuring isometric shoulder rotational strength. Cross-sectional study. Biomechanics laboratory. Thirty-nine young, healthy participants. The peak isometric strength of the internal rotators and external rotators, measured by handheld dynamometry (in newton) and isokinetic dynamometry (in newton meter). Maximal isometric shoulder rotational strength was measured as participants lay supine with 90° shoulder abduction, neutral rotation, 90° elbow flexion, and forearm pronation. Measurements were performed independently by 2 different physiotherapists and in 3 different sessions to evaluate interrater and intrarater reliability. The data obtained by handheld dynamometry were compared with those obtained by isokinetic testing to evaluate concurrent validity. The intraclass correlation coefficients for interrater reliability in measuring maximum isometric shoulder external and internal rotation strength were .914 (95% confidence interval [CI], .842-.954) and .842 (95% CI, .720-.914), respectively. The intrarater reliability values of the method for measuring maximal shoulder external and internal rotation strength were 0.865 (95% CI, 0.757-0.927) and 0.901 (95% CI, 0.820-0.947), respectively. The Pearson correlation coefficients between the handheld and isokinetic dynamometer measurements were .792 (95% CI, .575-.905) for external rotation strength and .664 (95% CI, .419-.839) for internal rotation strength. The handheld dynamometer showed good to excellent reliability and moderate to good validity in measuring maximum isometric shoulder rotational strength. Therefore, handheld dynamometry could be acceptable for health and sports professionals in field situations to evaluate maximum isometric shoulder rotational strength.

In this study, we compared the intertrial reliability of resistive torque measurements obtained with hand-held and isokinetic dynamometers and examined the validity of the hand-held dynamometers for the assessment of spastic hypertonia, defined as reflex- and nonreflex-induced resistance to stretch. Nine subjects (mean age = 40.6 years) with a chronic (1-5 years) spinal cord injury participated. The plantar flexors were stretched at 5 degrees /s (low velocity [LV]) and 180 degrees /s (high velocity [HV]) with an isokinetic dynamometer while the evaluator attempted to match these velocities with a hand-held dynamometer. Electromyographic activity of the soleus and tibialis anterior muscles as well as ankle displacements were recorded. Resistive torque and velocity, measured at -5 degrees of dorsiflexion, were averaged (n = 4). High intraclass correlation coefficients (ICCs) were found at LV and HV for both the hand-held (ICC = .93 and .84) and isokinetic (ICC = .99 and .93) dynamometers. With the hand-held dynamometer, lower resistive torques were found at LV (0.8 N.m) and HV (1.2 N.m), whereas higher velocities were attained at HV. The results indicate that the reproducibility of resistive torques obtained with hand-held dynamometry compares with that obtained with isokinetic dynamometry and allows testing of velocities that can be adjusted to the specific level of resistance to stretch. Electromyography confirmed the validity of hand-held dynamometry for assessing reflex and nonreflex components of SH. [Lamontagne A, Malouin F, Richards CL, Dumas F. Evaluation of reflex- and nonreflex-induced muscle resistance to stretch in adults with spinal cord injury using hand-held and isokinetic dynamometry.

Objectives:Hip and knee strength abnormalities have been implicated in patellofemoral pain (PFP) in multiple studies in the recent literature. However, many authors have noted that hip muscle weakness has not yet been defined as having a causal relationship to PFP due to the fact that many studies used subjects already diagnosed with PFP. The purpose of this study was to compare prospective hip and knee isokinetic strength measures in young females who subsequently went on to develop PFP relative to their uninjured healthy peers.Methods:Middle and high school female athletes (n=255) were evaluated by a physician for PFP prevalence. Isokinetic strength measurements of the knee (flexion and extension at 300°/sec) and hip (abduction at 120°/sec) were obtained prior to the start of their basketball and soccer seasons. Isokinetic torque measures (newton*meters) were normalized to leg length by mass and are described as a normalized torque (NT). Those diagnosed with PFP at pre-season were excluded and the remaining athletes were monitored by certified athletic trainers for PFP incidence during their competitive seasons. A one-way ANOVA was used to determine significant differences in knee and hip strength measures between the incident PFP and the control groups.Results:Young females who developed PFP were not different in age 12.6 ± 0.9 yrs., mass 51.4 ± 13.2 kg, height 158.8 ± 7.3 cm, or leg length 83.8 ± 4.2 cm compared to the referent control group (P>0.05). Females who developed PFP demonstrated increased normalized hip strength 0.013 ± 0.003 NT relative to the referent control group 0.011 ± 0.003 NT (P<0.05). Normalized knee extension and knee flexion strength were not different between the females with incident PFP compared to the referent control group (P>0.05).Conclusion:The findings in this study indicate that young females with greater hip abduction strength may be at an increased risk for the development of PFP. Previous studies that have looked at landing biomechanics indicated that those with PFP have increased knee abduction and increased hip adduction during landing. Combining our current data and previous literature, we theorize that greater hip abduction strength may be a resultant symptom of increased eccentric loading of the hip abductors associated with increased dynamic valgus biomechanics demonstrated to underlie increased PFP incidence. Future research is warranted to dissect the relative contributions of hip strength and recruitment and dynamic valgus alignments during landing to the pathomechanics of PFP.

Introduction: The sphygmomanometer test is an alternative and inexpensive method for assessment of muscle strength. This instrument was considered valid and reliable to measure the isometric strength in different health conditions, however, in individuals with limb amputations the properties of this instrument for this purpose, have not been investigated. Objective: To investigate the concurrent criterion validity, test-retest and inter-rater reliabilities of the aneroid sphygmomanometer test (AST) without modification, for assessment of the strength of subjects with lower limb amputations. Methods: Twenty-two subjects (57.6 ± 15.2 years) with lower limb amputations were included in this study. Maximum isometric force was assessed with a handheld dynamometer (microFet2®) and the AST. To identify differences between trials, one-way ANOVA was applied. To assess the concurrent criterion validity, test-retest and inter-rater reliabilities of the AST, Pearson’s correlation coefficients of determination and intra-class correlation coefficient (ICC) were calculated. Results: For all muscle groups, no differences were observed between the trials (0.00001 ≤ F ≤ 0.10; 0.90 ≤ p ≤ 0.99). Significant, positive, and high to very high correlations were found between the HHD and the AST measures for the different numbers of trials for all assessed muscles (0.76 ≤ r ≤ 0.93; p ≤ 0.02). Test-retest (0.67 ≤ ICC ≤ 0.97) and inter-rater reliabilities (0.78 ≤ ICC ≤ 0.97) were adequate. The values obtained with the AST were good predictors of those obtained with HHD (0.58 ≤ r2 ≤ 0.85). Conclusion: For individuals with lower limb amputation, the AST showed adequate concurrent criterion validity, test-retest reliability and inter-rater reliability for the assessment of lower limbs muscle strength.

Knee and hip strength measurements obtained by a hand-held dynamometer stabilized by a belt and an examiner demonstrate parallel reliability but not agreement

To assess the relationship between rate of change in muscle strength and all-cause mortality. Prospective observational study of the causes and course of physical disability. Twelve contiguous ZIP code areas in Baltimore, Maryland. Three hundred seven community-dwelling women aged 70 to 79 at study baseline. The outcome was all-cause mortality (1994-2009); predictors included up to seven repeated measurements of handgrip, knee extension, and hip flexion strength, with a median follow-up time of 10 years. Demographic factors, body mass index, smoking status, number of chronic diseases, depressive symptoms, physical activity, interleukin-6, and albumin were assessed at baseline and included as confounders. The associations between declining muscle strength and mortality were assessed using a joint longitudinal and survival model. Grip and hip strength declined an average of 1.10 and 1.31 kg/year between age 70 and 75 and 0.50 and 0.39 kg/year thereafter, respectively; knee strength declined at a constant rate of 0.57 kg/year. Faster rates of decline in grip and hip strength, but not knee strength, independently predicted mortality after accounting for baseline levels and potential confounders (hazard ratio (HR) = 1.33, 95% confidence interval (95% CI) = 1.06-1.67, HR = 1.14, 95% CI = 0.91-1.41, and 2.62, 95% CI = 1.43-4.78 for every 0.5 standard deviation increase in rate of decline in grip, knee, and hip strength, respectively). Monitoring the rate of decline in grip and hip flexion strength in addition to absolute levels may greatly improve the identification of women most at risk of dying.

To define the relationship between Functional Movement Screen (FMS) scores and hop performance, hip strength, and knee strength in collegiate football players. Cross-sectional cohort. Freshmen of a Division I collegiate American football team (n = 59). The athletes performed the FMS, and also a variety of hop tests, isokinetic knee strength, and isometric hip strength tasks. We recorded total FMS score, peak strength, and hop performance, and we calculated asymmetries between legs on the different tasks. Spearman correlation coefficients quantified the relationships between these measures, and χ analyses compared the number of athletes with asymmetries on the different tasks. We observed significant correlations (r = 0.38-0.56, P ≤ 0.02) between FMS scores and hop distance but not between FMS scores and hip or knee strength (all P ≥ 0.21). The amount of asymmetry on the FMS test was significantly correlated to the amount of asymmetry on the timed 6-m hop (r = 0.44, P < 0.01) but not to hip or knee strength asymmetries between limbs (all P ≥ 0.34). Functional Movement Screen score was positively correlated to hop distance, and limb asymmetry in FMS tasks was correlated to limb asymmetry in 6-m hop time in football players. No significant correlations were observed between FMS score and hip and knee strength or between FMS asymmetry and asymmetries in hip and knee strength between limbs. These results indicate that a simple hop for distance test may be a time-efficient and cost-efficient alternative to FMS testing in athletes and that functional asymmetries between limbs do not coincide with strength asymmetries.

Hannon, JP, Wang-Price, S, Garrison, JC, Goto, S, Bothwell, JM, and Bush, CA. Normalized hip and knee strength in two age groups of adolescent female soccer players. J Strength Cond Res 36(1): 207-211, 2022-Limb symmetry strength measures are used for clinical decision-making considering when an athlete is ready to return to sport after anterior cruciate ligament (ACL) injuries. However, changes in bilateral muscle strength occur after ACL injury resulting in potentially altered limb symmetry calculations. Adolescent female soccer players are at increased risk of sustaining ACL injuries. Published age and sex-matched strength values in this population may be of benefit to clinicians to improve clinical decision-making. The purpose of this study was to establish normative hip and knee strength data of both the dominant and nondominant limbs in adolescent female soccer players. Sixty-four female soccer players (ages 10-18) were enrolled in this study. Subjects were divided by age into 2 groups (group 1: 10-14 years; group 2: 15-18 years). Subjects underwent Biodex isokinetic strength testing at 60°·s-1 and 180°·s-1 to assess quadriceps and hamstring strength. Isometric hip strength (abduction and external rotation) was measured using a hand-held dynamometer. No significant differences were found between groups on either limb in regards to quadriceps or hamstring strength. No significant differences were found between groups on either limb for hip external rotation strength. Significant differences in hip abduction strength were found between groups on the dominant (group 1: 0.21 ± 0.04; group 2: 0.18 ± 0.04; p = 0.014) and nondominant (group 1: 0.21 ± 0.05; group 2: 0.18 ± 0.05; p = 0.019) limbs. The results of this study shed light on normative strength values for a high-risk injury population.

To examine the relative and absolute interrater reliability of handheld dynamometers (HHD) for assessing the lower extremity muscle strength, maximal voluntary contractions (MVCs) of 16 young adults for bilateral hip and knee muscles were tested using the break method. Three MVCs of each muscle group were required for obtaining the muscle strength. Participants' muscle strengths were tested by 2 raters. The intraclass correlation coefficients (ICCs) and the smallest real differences (SRD) were used to examine the relative and absolute reliabilities, and the Bland-Altman analyses were used to check whether systematic bias exists. The results showed that the relative reliabilities of all muscle groups were excellent (ICCs = 0.83-0.92) except for the knee extensors (ICC = 0.60). The SRD represents the smallest difference that indicates a real change for a single subject. The SRD% of all muscle groups was acceptable (ranging from 8.4 to 22.8 %), with the hip extensors being the smallest and knee extensors being the largest. The reliability of the knee extensors was unsatisfactory because of poor relative and absolute reliabilities and systematic bias. In addition to assessing the relative reliability in strength measurement, the absolute reliability provides the data of the measurement error, which is useful information in clinical practice to know whether the change in strength of a subject is real. Hand-held dynamometer is a reliable tool for quantifying most of the hip and knee strength except for the knee extensors. Modifying the measuring technique for knee extension is needed in future studies to improve the reliability.

The aim of this study was to test the correlation between knee-to-hip flexion ratio during a single leg landing task and hip and knee strength, and ankle range of motion. Twenty-four male participants from a professional soccer team performed a continuous single leg jump-landing test during 10s, while lower limb kinematics data were collected using a motion analysis system. After biomechanical testing, maximal isometric hip (abduction, extension, external rotation), knee extension and flexion strength were measured. Maximum ankle dorsiflexion range of motion was assessed statically using the weight bearing lunge test. Pearson correlation coefficients were calculated to determine the associations between the predictor variables (knee and hip strength, and ankle ROM) and the main outcome measure (knee-to-hip flexion ratio). Correlation between knee-to-hip flexion ratio and hip abductors strength was significant (r = −0.47; p = 0.019). No other significant correlations were observed among the variables (p > 0.05). These results demonstrated that a lower hip abductors strength in male soccer players was correlated with a high knee-to-hip flexion ratio during landing from a single leg jump, potentially increasing knee overload by decreasing energy absorption at the hip. The results provide a novel proposal for the functioning of hip muscles to control knee overload.

Do novice runners have weak hips and bad running form?

Insufficient lower extremity strength may be a risk factor for lower extremity injuries such as noncontact anterior cruciate ligament tears. Therefore, clinicians need reliable instruments to assess strength deficiencies. To assess the intrarater, interrater, intrasession, and intersession reliability of a portable fixed dynamometer in measuring the strength of the hip and knee musculature. Crossover study. Sports medicine research laboratory. Three raters (A, B, C) participated in this 2-phase study. Raters A and B tested 11 healthy college graduate students (2 men, 9 women) in phase 1. Raters A and C tested 26 healthy college undergraduate students (7 men, 19 women) in phase 2. The dependent variables for the study were hip adductor, hip abductor, hip flexor, hip extensor, hip internal rotator, hip external rotator, knee flexor, and knee extensor peak force. The phase 1 intrasession intraclass correlation coefficients for sessions 1, 2, and 3 ranged from 0.88 to 0.99 (SEM = 0.08-3.02 N), 0.85 to 0.99 (SEM = 0.26-3.88 N), and 0.92 to 0.96 (SEM = 0.52-2.76 N), respectively. Intraclass correlation coefficients ranged from 0.57 to 0.95 (SEM = 1.72-13.15 N) for phase 1 intersession values, 0.70 to 0.94 (SEM = 1.42-9.20 N) for phase 2 intrarater reliability values, and 0.69 to 0.88 (SEM = 1.20-8.50 N) for phase 2 interrater values. The portable fixed dynamometer showed good to high intrasession and intersession reliability values for hip and knee strength. Intrarater and interrater reliability were fair to high, except for hip internal rotation, which showed poor reliability.