Validity and Test-Retest Reliability of a Novel Push Low-Cost Hand-Held Dynamometer for Knee Strength Assessment during Different Force Ranges

The objective was to assess the instrumental validity and the test–retest reliability of a low-cost hand-held push dynamometer adapted from a load-cell based hanging scale (tHHD) to collect compressive forces in different ranges of compressive forces. Three independent raters applied 50 pre-established compressions each on the tHHD centered on a force platform in three distinct ranges: ~70 N, ~160 N, ~250 N. Knee isometric strength was also assessed on 19 subjects in two sessions (48 h apart) using the tHHD anchored by an inelastic adjustable strap. Knee extension and flexion were assessed with the participant seated on a chair with the feet resting on the floor, knees, and hips flexed at 90°. The isometric force peaks were recorded and compared. The ICC and the Cronbach’s α showed excellent consistency and agreement for both instrumental validity and test–retest reliability (range: 0.89–0.99), as the correlation and determination coefficients (range: 0.80–0.99). The SEM and the MDC analysis returned adequate low values with a coefficient of variation less than 5%. The Bland–Altman results showed consistency and high levels of agreement. The tHHD is a valid method to assess the knee isometric strength, showing portability, cost-effectiveness, and user-friendly interface to provide an effective form to assess the knee isometric strength.

Knee Flexor Eccentric Strength, Hamstring Muscle Volume and Sprinting in Elite Professional Soccer Players with a Prior Strained Hamstring

The aim was to determine if players with a prior hamstring strain injury (HSI) exhibit bilateral deficits in knee flexor eccentric strength and hamstring muscle volume and differences in sprinting performance compared with players without a history of HSIs. Forty-six male professional soccer players participated in this study. Eccentric knee flexor strength, hamstring muscle volume (MRI), and a 20-m running sprint test (5- and 10-m split time) were assessed at the start of the preseason. Eccentric knee strength of the previously injured limbs of injured players was greater (ES: 1.18–1.36) than the uninjured limbs in uninjured players. Previously injured limbs showed possibly larger biceps femoris short heads (BFSh) and likely semitendinosus (ST) muscle volumes than the contralateral uninjured limbs among the injured players (ES: 0.36) and the limbs of the uninjured players (ES: 0.56), respectively. Players who had experienced a previous HSI were possibly slower in the 5-m (small ES: 0.46), while unclear differences were found in both the 10-m and 20-m times. Players with a prior HSI displayed greater eccentric knee flexor strength, possibly relatively hypertrophied ST and BFSh muscles, and possibly reduced 5-m sprinting performances than previously uninjured players. This can have implication for the design of secondary hamstring muscle injury prevention strategies.

Relationship Between Isokinetic Knee Strength and Single-Leg Drop Jump Performance 9 Months After ACL Reconstruction

Background: Deficits in knee strength after anterior cruciate ligament reconstruction (ACLR) surgery are common. Deficits in the single-leg drop jump (SLDJ), a test of plyometric ability, are also found. Purpose: To examine the relationship between isokinetic knee strength, SLDJ performance, and self-reported knee function 9 months after ACLR. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Knee isokinetic peak torque, SLDJ jump height, contact time, and reactive strength index (RSI), as well as International Knee Documentation Committee (IKDC) scores were assessed in 116 male, field-sport athletes at 9.2 months after ACLR. SLDJ testing took place in a 3-dimensional biomechanics laboratory. Linear regression models were used to analyze the relationship between the variables. Results: A significant relationship was found between ACLR-limb isokinetic knee extensor strength and SLDJ jump height ( P < .001, r 2 = 0.29) and RSI ( P < .001, r 2 = 0.33), and between ACLR-limb isokinetic knee flexor strength and SLDJ jump height ( P < .001, r 2 = 0.12) and RSI ( P < .001, r 2 = 0.15). A significant positive relationship was also found between knee extensor asymmetry and SLDJ jump height asymmetry ( P < .001, r 2 = 0.27) and SLDJ reactive strength asymmetry ( P < .001, r 2 = 0.18). Combined ACLR-limb jump height and contact time best predicted IKDC scores ( P < .001, r 2 = 0.12). Conclusion: Isokinetic knee extension strength explained approximately 30% of SLDJ performance, with a much weaker relationship between knee flexion strength and SLDJ performance. Isokinetic strength and SLDJ performance were weak predictors of variation in IKDC scores.

Validity and Test-Retest Reliability of a Novel Push Low-Cost Hand-Held Dynamometer for Knee Strength Assessment During Different Force Ranges

The objective was to assess the instrumental validity and the test-retest reliability of a low-cost hand-held push dynamometer adapted from a load-cell based hanging scale (tHHD) to collect compressive forces in different ranges of compressive forces. Three independent raters applied 50 pre-established compressions each on the tHHD centered on a force platform in 3 distinct ranges: ~70 N, ~160 N, ~250 N. Knee isometric strength was also assessed on 19 subjects in two sessions (48h apart) using the tHHD anchored by an inelastic adjustable strap. Knee extension and flexion were assessed with the participant seated on a chair with the feet resting on the floor, knees, and hips flexed at 90&deg;. The isometric force peaks were recorded and compared. The ICC and the Cronbach&rsquo;s &alpha; showed excellent consistency and agreement for both instrumental validity and test-retest reliability, as the correlation and determination coefficients. The SEM and the MDC analysis returned adequate low values with a coefficient of variation less than 5%. The Bland-Altman results showed consistency and high levels of agreement. The tHHD is a valid method to assess the knee isometric strength, showing portability, cost-effectiveness, and user-friendly interface to provide an effective form to assess the knee isometric strength.

Relationships Between Physical Function and Psychological Readiness to Return to Sport After Anterior Cruciate Ligament Reconstruction

Background: Information about specific factors of physical function that contribute to psychological readiness is needed to plan rehabilitation for a return to sports. The purpose of this study was to identify specific physical functions related to the psychological readiness of patients aiming to return to sports 6 months after reconstruction. We hypothesized that the knee strength is a factor related to the Anterior Cruciate Ligament–Return to Sport After Injury Scale (ACL-RSI) cutoff score for a return to sports at 2 years after reconstruction.Methods: Fifty-four patients who had undergone primary reconstruction using hamstring tendon participated in this study. Psychological readiness was measured using the ACL-RSI in patients at 6 months after reconstruction. To identify specific physical functions related to the ACL-RSI score, participants were divided into groups with ACL-RSI scores of ³60 or <60. Non-paired t-tests or the Mann-Whitney test were performed to analyze group differences in objective variables in physical function: 1) knee strength in both legs; 2) leg anterior reach distance on both sides; and 3) single-leg hop (SLH) distances in three directions for both legs.Results: Significant differences between groups were identified in knee flexion strength (60°/s) for the uninvolved limb, hamstring-to-quadriceps ratio (60°/s) for the uninvolved limb, knee flexion strength (180°/s) for the involved limb, limb symmetry index (LSI) of leg anterior reach distance, the ratio of the distance to the height of the patient and LSI of SLH distances in lateral and medial directions. Conclusion: This study revealed that at 6 months after reconstruction, increased knee flexion strength (Ratio of the peak torque measured to the body mass of the patient), hamstring-to-quadriceps ratio, leg anterior reach distance LSI, and lateral and medial SLH appear important to exceed the ACL-RSI cutoff for a return to sports at 2 years after reconstruction. The present results may be useful for planning post-operative rehabilitation for long-term return to sports after reconstruction.

Assessment of Isokinetic Knee and Shoulder Strength in Elite Youth Boxers: Correlation with Punch Impact Force

This study aimed to assess the isokinetic strength performance of the knee and shoulder in amateur boxer, and further to explore the contribution of knee and shoulder peak torque to different punches. Boxers (6 females and 8 males) were measured the dynamic concentric torque of knee flexion(F) and extension(E), shoulder external rotation (ER) and internal rotation (IR) at 60°/S, 180°/S. We tested the punching force of three techniques by Kistler Instruments. At 60°/S, F/E ratios of the dominant (D) knee of female boxers were lower than those of non-dominant (ND) side (p=0.03). At two angular velocities, all boxers demonstrated higher ER/IR ratios in ND (p=0.011 for males, p=0.025 for females). Bilateral difference of knee flexor in females was greater (p=0.038) than that in males. The maximum correlation was found at 180°/S between punching forces and the joints strength. ANOVA analyses revealed that athletes with greater punching force tend to have higher knee strength. Although correlations between shoulders strength and punching forces were strong, they did not discriminate between athletes who punched with higher punching force. In order to effectively transfer muscle strength to punching force, rapid completion of action should be highlighted in strength training, especially lower-limb strength.

Knee Strength and Ankle Range of Motion Impacts on Timed Function Tests in Duchenne Muscular Dystrophy: In the Era of Glucocorticoids

Background: Duchenne Muscular Dystrophy (DMD) is a neuromuscular disorder that presents in childhood and is characterized by slowly progressive proximal weakness and lower extremity contractures that limit ambulatory ability [1, 2]. Contractures develop in the ankles, knees, and hips due to muscle imbalances, fibrotic changes, loss of strength, and static positioning [2, 5]. Currently, standards of care guidelines emphasize the importance of maintaining good musculoskeletal alignment through stretching, bracing, and glucocorticoid (GC) therapy to preserve strength and function. Methods: This is a retrospective analysis of prospectively collected data through the CINRG Duchenne Natural history study (DNHS). The objectives of this analysis are to understand the progression of ankle contractures for individuals with DMD and to investigate the relationship between progressive lower limb contractures, knee strength, and Timed Function Tests. A collection of TFTs including supine to stand (STS), 10 meter walk test (10MWT), and timed stair climbing (4SC) have been used to monitor disease progression and are predictive of loss of ambulation in these patients [4]. Multiple factors contribute to loss of ambulation, including progressive loss of strength and contracture development that leads to changing biomechanical demands for ambulation. A better understanding of the changes in strength and range of motion (ROM) that contribute to loss of function is important in a more individualized rehabilitation management plan. In this longitudinal study, we measured strength using quantitative muscle testing (QMT) with the CINRG Quantitative Measurement System (CQMS)), ROM was measuresed with a goniometer and TFTs were measured using a standard stopwatch and methodology. Results: We enrolled 440 participants; mean baseline age was 8.9 (2.1, 28.0) years with 1321 observations used for analysis. GC use was stratified based on duration on drug with 18.7%at < 6 months or naïve; 4.3%<1 year; 58.0%1 < 10 years; and 19.3%between 10-25 years of GC use. Ankle ROM was better for those on GC compared to GC naive but did not significantly influence long-term progression rates. QMT, ROM, age and GCs contribute to speed of TFTs. Knee extension (KE) strength and Dorsiflexion (DF) ROM are significant predictors of speed for all TFTs (p < 0.001). Of the variables used in this analysis, KE strength is the primary predictor of walking speed, estimating that every pound increase in KE results in a 0.042 m/s improvement in 10MWT, and a smaller similar increase of 0.009 m/s with every degree of ankle DF ROM. Conclusion: GC use provides an improvement in strength and ROM but does not affect rate of change. Knee strength has a greater influence on speed of TFTs than DF ROM, although both are statistically significant predictors of speed. Results show that retaining knee strength [1, 2], along with joint flexibility, may be important factors in the ability to perform walking, climbing and supine to stand activities.

Establishing Reference Values for Isometric Knee Extension and Flexion Strength

Single-joint isometric and isokinetic knee strength assessment plays an important role in strength and conditioning, physical therapy, and rehabilitation. The literature, however, lacks absolute reference values. We systematically reviewed the available studies that assessed isometric knee strength. Two scientific databases (PubMed and PEDro) were searched for the papers that are published from the inception of the field to the end of 2019. We included studies that involved participants of both genders and different age groups, regardless of the study design, that involved isometric knee extension and/or flexion measurement. The extracted data were converted to body-mass-normalized values. Moreover, the data were grouped according to the knee angle condition (extended, mid-range, and flexed). A meta-analysis was performed on 13,893 participants from 411 studies. In adult healthy males, the pooled 95% confidence intervals (CI) for knee extension were 1.34–2.23Nm/kg for extended knee angle, 2.92–3.45Nm/kg for mid-range knee angle, and 2.50–3.06Nm/kg for flexed knee angle, while the CIs for flexion were 0.85–1.20, 1.15–1.62, and 0.96–1.54Nm/kg, respectively. Adult females consistently showed lower strength than adult male subgroups (e.g., the CIs for knee extension were 1.01–1.50, 2.08–2.74, and 2.04–2.71Nm/kg for extended, mid-range, and flexed knee angle condition). Older adults consistently showed lower values than adults (e.g., pooled CIs for mid-range knee angle were 1.74–2.16Nm/kg (male) and 1.40–1.64Nm/kg (female) for extension, and 0.69–0.89Nm/kg (male) and 0.46–0.81Nm/kg (female) for flexion). Reliable normative for athletes could not be calculated due to limited number of studies for individual sports.

Knee strength measurement: Can we switch between isokinetic dynamometers?

BACKGROUND: Isokinetic evaluation is considered the gold standard in muscle strength measurement due to its sensitivity, intra-dynamometer reproducibility and usefulness in the injury prevention screening and follow up of subjects with musculoskeletal pathologies, neurological disease or after surgical operation. However, can one switch among different isokinetic dynamometers for the purpose of knee muscles evaluation? OBJECTIVES: To comprehensively evaluate the compatibility of the isokinetic short concentric and eccentric strength evaluation protocol and of the fatigability resistance evaluation between three different isokinetic devices. METHODS: Eighteen recreationally active men underwent three isokinetic knee testing sessions on three different isokinetic devices with 7–10 days of rest between each session. Relative (Pearson’s r product-moment correlation coefficient – PCC) and absolute (standard error of measurement – SEM, Cohen effect sizes (d) and probabilistic inferences – MBI) parameters of reproducibility were determined to assess the inter-dynamometer agreement. RESULTS: For the short concentric and eccentric strength evaluation protocol, the extensors in concentric mode and the flexors in eccentric mode can be compared (eventually with transposition formulas provided) between Biodex, Con-Trex and Cybex (almost all PCC ⩾ 0.80). The DCR could be compared between Con-Trex and Cybex and between Biodex and Cybex pairs (eventually with transposition formula provided). For the fatigability resistance evaluation protocol, the total sum can be compared for extensors (eventually with transposition formulas provided) for PM for all dynamometer pairs considered and, in the case of MW, only for Biodex and Con-Trex (PCC ⩾ 0.80). CONCLUSIONS: Only some of the parameters derived either from the short concentric and eccentric strength evaluation protocol or the fatigability resistance evaluation protocol may be interchangeable providing transposition formulas are applied. Otherwise, isokinetic findings are largely system-dependent save some specific instances.

HURDLE STEP COMPONENT SCORE FROM THE FUNCTIONAL MOVEMENT SCREEN IS ASSOCIATED WITH STRENGTH, SPEED, AND JUMP PERFORMANCE

Background: The Functional Movement Screen (FMS) is a tool designed to establish a baseline for fundamental movement capacity, highlight limitations and limb asymmetries, and identify potential injury risk. Previous research has shown that individual components of the screen are also indicative of injury risk, as well as potential predictors of athletic performance unlike the FMS composite scores. However, this literature is limited and lacks statistical power. Identifying which component scores are predictive of injury risk and athletic performance would provide a quick, powerful tool for coaches and trainers to evaluate athletes. Purpose: To determine if individual component scores of the FMS are associated with athletic performance in highly-active youth athletes. Methods: Youth athletes participated in the Specialized Athlete Functional Evaluation (SAFE) Program. Data collection was extensive, however, for the purpose of this abstract, only a selection of data was analyzed – age, BMI, years played, total number of past injuries, isokinetic knee strength, 10- and 20-meter sprint, single-leg hop (SLH) distance, and FMS scores. Seated knee flexion/extension strength was collected at 120°/second using a Biodex System 4, and peak torque was normalized by body weight. The maximum distance of three SLHs was recorded for each leg and normalized to leg length. FMS scores used for analysis included the total composite and component scores, including the deep squat, hurdle step, in-line lunge, shoulder mobility, active straight-leg raise, trunk stability push-up, and rotary stability. Wilcoxon Signed Ranks Tests were used to determine side-to-side differences, and Kruskal-Wallis tests were performed to determine differences in athletic performance based on FMS scores ( α<0.05). Results: A total of 38 highly-active, youth athletes (26F; 15.4±2.6 years; BMI 21.0±5.3) were tested. Participants reported playing organized sports for 8.7±3.4 years, having 2.0±1.2 past sports-related injuries, and 74% reported specializing in a single sport. No side-to-side differences were found. While the composite FMS score significantly differed by number of past injuries ( p=0.036), it was not associated with athletic performance. Alternatively, left knee strength, sprint speeds, and right hop distance significantly differed by the hurdle step component score (Table 1). Conclusion: While the composite FMS score was not an indicator of athletic performance, the hurdle step component score was associated with strength, speed, and jump performance. This individual task could be a beneficial tool for coaches and trainers when evaluating athletic ability and injury risk of athletes. Tables/Figures: [Table: see text]