The evaluation of rate of force development during rapid contractions has recently become quite popular for characterising explosive strength of athletes, elderly individuals and patients. The main ...aims of this narrative review are to describe the neuromuscular determinants of rate of force development and to discuss various methodological considerations inherent to its evaluation for research and clinical purposes. Rate of force development (1) seems to be mainly determined by the capacity to produce maximal voluntary activation in the early phase of an explosive contraction (first 50–75 ms), particularly as a result of increased motor unit discharge rate; (2) can be improved by both explosive-type and heavy-resistance strength training in different subject populations, mainly through an improvement in rapid muscle activation; (3) is quite difficult to evaluate in a valid and reliable way. Therefore, we provide evidence-based practical recommendations for rational quantification of rate of force development in both laboratory and clinical settings.
Quadriceps strength testing is recommended to guide rehabilitation and mitigate the risk of second injury following anterior cruciate ligament (ACL) reconstruction. Hand-held dynamometry is a ...practical alternative to electromechanical dynamometry but demonstrates insufficient reliability and criterion validity in healthy and ACL-reconstructed participants respectively. The purpose of this study is to investigate the reliability and concurrent validity of inline dynamometry for measuring quadriceps strength. The hypotheses are that intra-class correlation coefficient (ICC) values will be >0.90 for reliability and concurrent validity.
This was a cross sectional study using a within-participant, repeated measures design. Isometric quadriceps testing was performed at 60° knee flexion in 50 healthy and 52 ACL-reconstructed participants. Interrater reliability, intrarater reliability, and concurrent validity of inline dynamometry was investigated through calculation of ICCs, Bland-Altman analysis, linear regression, standard error of measurement (SEM) and minimal detectable change (MDC).
The lower bounds of the 95% confidence intervals were >0.90 for all reliability and validity ICCs in healthy and ACL-reconstructed participants, except for intrarater reliability in healthy participants using absolute scores (ICC = 0.936 95% CI 0.890–0.963). In ACL-reconstructed participants, Bland-Altman bias was 0.01 Nm/kg for absolute and average scores, limits of agreement were −11.74% to 12.59% for absolute scores, the SEM was 0.13Nm/kg (95% CI 0.10–0.17) and the MDC was 0.36Nm/kg (95% CI 0.28 – 0.47).
Inline dynamometry is a reliable and economical alternative to electromechanical dynamometry for the assessment of quadriceps strength following ACL-reconstruction.
Clinical trial registration number:ClinicalTrials.gov (NCT05109871)
Abstract
Objective
This study aimed to evaluate the intrarater and interrater reliability of isometric quadriceps strength (IQS) using a portable dynamometer in individuals with chronic obstructive ...pulmonary disease (COPD) and to verify their tolerance to the protocol.
Methods
A cross-sectional reliability study was conducted with 50 individuals with stable COPD (34 men and 16 women; mean age = 70 years SD = 8). The main outcome measure was obtained using a portable dynamometer (Microfet 2) to assess IQS. Two masked raters performed 2 assessments in the dominant lower limb on 2 nonconsecutive days. The intraclass correlation coefficient (ICC) was used to verify the intrarater and interrater reliability and was considered excellent when >0.90, with a 5% significance level.
Results
Rater 1 and 2 intrarater reliability was as follows: ICC = 0.96 (95% CI = 0.94 to 0.98) and ICC = 0.97 (95% CI = 0.95 to 0.98), respectively. The interrater reliability was as follows: ICC = 0.96 (95% CI = 0.93 to 0.98). The minimum detectable difference was 4 to 5 peak isometric strength, in mean, for intrarater and interrater reliability. Not all patients presented relevant changes in physiological responses, dyspnea, and lower limb fatigue.
Conclusion
There was an excellent intrarater and interrater reliability for IQS, and the participants tolerated the protocol.
Impact
This tool can be used to assess quadriceps strength in clinical practice in patients with COPD.
Upper-limb exoskeletons are gaining traction in industrial work environments. However, other than advertised general specifications (e.g., peak support angle), the support torque provided throughout ...the reach envelope is largely unknown to end users. As such, this paper describes a methodology for measuring the specific supportive torque provided by upper-limb exoskeletons. The support of four commercially available passive upper-limb exoskeletons was quantified using an isokinetic dynamometer for all support ranges and levels (n = 68). Tests were repeated four times to determine between-session reliability. Intraclass correlation coefficients demonstrated ‘Good’ to ‘Excellent’ reliability, except for one condition. Polynomial regression equations were developed for each condition to predict exoskeleton support for any upper-limb elevation angle between 10° and 180°. These equations can be used to approximate upper-limb exoskeleton support in digital human modeling assessments, or to aid selection of exoskeleton settings specific to a worker's anthropometry and work task location.
Display omitted
•Isokinetic dynamometers can reliably measure upper-limb exoskeleton support.•Provided equations estimate exoskeleton support based on upper-limb elevation angle.•Exoskeleton support can be implemented into digital human modeling software.•These equations enable selection of exoskeleton settings for worker anthropometry.
After anterior cruciate ligament reconstruction (ACLR), there are differences in the neuromuscular deficits observed in patients with bone‐patellar tendon‐bone (BPTB) and with hamstring tendon (HT) ...autografts. The differences in knee extensor and flexor strength are commonly reported, but analyses have largely focused on peak torque metrics despite the requirement to generate torque through range when returning to sport. The aim of this study was to investigate the angle‐specific strength and strength asymmetry differences between BPTB and HT around the time of return to play after ACLR. A total of 357 male field sport athletes with either a BPTB (n = 297) or an HT (n = 60) autograft underwent concentric knee flexor and extensor isokinetic strength testing 9 months post‐ACLR. Angle‐specific torques were compared between grafts and limbs using 1D Statistical Parametric Mapping and discrete‐point variables. Inter‐limb extensor torque asymmetry was greater in BTPB than HT at knee angles of >30° (p = 0.001, peak d = 5.53), with flexor torque asymmetry lower in BPTB than HT at flexion angles of >25° (p = 0.001, peak d = 2.68). Angle of maximum asymmetry and angle of operated limb peak torque differed in knee extension for BPTB (p < 0.001, d = 0.32) but not HT, whereas knee flexion angle of maximum asymmetry and operated limb peak torque differed in both BTPB (p < 0.001, d = 0.75) and HT (p < 0.001, d = 0.43). Graft type affected extensor torque at knee angles of 67°–85° and flexor torque at knee angles of 27°–85°. Angle‐specific strength analysis may inform the rehabilitation process and improve rehabilitation and return‐to‐play decision making strategies in comparison with the use of peak torque values alone.
Resistance training is a widely used method to enhance muscle strength, with acute program variables influencing muscle adaptations. This study focused on the often-neglected variable of inter-set ...rest interval duration and its impact on muscle strength gains. Existing literature presents conflicting findings, with some studies advocating for longer rest intervals, while the others show comparable strength increases with shorter rests. Methodological differences in prescription and sample groups contributed to these inconsistencies. This study investigated the effect of short and long inter-set rests on maximal isokinetic strength gains of the upper and lower extremities during slow and fast angular velocities after eight weeks of resistance training. The research involved 26 healthy strength-trained males (age=20±1 year, body mass=81.5±8.8 kg, body height=184.4±6.1 cm) randomly assigned to G1m (1-minute rest) or G3m (3-minute rest). The resistance training programs were matched for all acute program variables, emphasizing the rest interval as the primary difference. Isokinetic dynamometry pre- and post-training assessed knee and elbow extensor and flexor maximal strength at 60º/s and 120º/s. The training program consisted of seven exercises performed at 70% 1RM until muscle failure three times per week over eight weeks. The most important result was that G3m, in contrast to G1m, led to a higher increase in peak torque of the knee (p=.037) and elbow extensors (p=.007) as well as the elbow flexors (p=.045) at 60º/s. Furthermore, G3m and G1m similarly increased the peak torque of the knee and elbow extensors and flexors at 120º/s and of the knee flexors at 60º/s (p>.138). In conclusion, the study suggests that strength training with longer inter-set rest intervals may lead to similar strength gains as strength training with shorter inter-set rest intervals. Nonetheless, individuals who prioritize maximizing their strength gains are advised to utilize longer rest intervals. However, shorter rest intervals may still yield significant strength enhancements, particularly for those who are limited by time.
to investigate the associations between initial level and rate of change in grip strength (GS) and all-cause mortality in very old adults (≥85 years) over a 9.6-year follow-up.
prospective mortality ...data from 845 participants in the Newcastle 85+ Study were analysed for survival in relation to GS (kg, baseline and 5-year mean change) using Cox proportional hazards models.
during the follow-up, 636 (75.3%) participants died. Higher baseline GS was associated with a decreased risk of mortality in all participants hazard ratio (HR) = 0.95, 95% confidence interval (CI): 0.93-0.98, P < 0.001, men (HR = 0.97, 95% CI: 0.95-0.99, P = 0.009) and women (HR = 0.96, 95% CI: 0.94-0.99, P = 0.007) after adjustment for health, lifestyle and anthropometric factors. Overall GS slope had a downward trajectory and was determined in 602 participants: 451 experienced constant decline (negative slope) and 151 had increasing GS (positive slope) over time. Men and women with a negative slope had a 16 and 33% increased risk of mortality, respectively, with every kg/year decline in GS (P ≤ 0.005), and participants with a positive slope had a 31% decreased risk of mortality (P = 0.03) irrespective of baseline GS and key covariates.
higher baseline GS and 5-year increase in GS were protective of mortality, whilst GS decline was associated with an increased risk of mortality in the very old over 9.6 years, especially in women. These results add to the biological and clinical importance of GS as a powerful predictor of long-term survival in late life.
Muscle imbalance and deficit are key parameters for guiding rehabilitation and sports sessions and avoiding injuries. However, the high cost and non-portable nature of most instruments employed for ...muscle strength assessment frequently hamper an affordable evaluation in field conditions. This study evaluated the validity and reliability of a low-cost digital dynamometer to assess the maximal isometric strength of upper limb muscles. Fourteen physically active volunteers performed the main movements of the upper limb at maximal isometric strength: flexion-extension, internal-external rotation and abduction-adduction of the shoulder; and flexion-extension of both elbow and wrist. Validity was examined by comparing the strength values from the low-cost digital dynamometer and those measured by an isokinetic dynamometer, assumed as the gold standard. The correlation between both devices was perfect (r > 0.913), while Bland-Altman plots showed absolute agreement between both devices, the maximum range of the values of bias was −0.99-1.00 N in wrist extension. Inter-tester and intra-tester reliability were excellent for all movements (ICC ≥ 0.855). The low-cost digital dynamometer showed strong validity and excellent reliability in assessing maximal isometric strength during the main movements of the upper limb. Professionals may use it for an affordable isometric muscle strength assessment in field situations.
Resumen: La evaluación de la fuerza en la mano es utilizada en ámbitos de salud y laborales, está compuesta por la fuerza de agarre y la fuerza de pellizco o fuerza pinch (Palmar Pinch - PP y Key ...Pinch - KP). La fuerza pinch ha sido poco estudiada y relacionada con variables antropométricas. El objetivo del presente trabajo fue determinar la relación entre la fuerza PP y KP con el género, la dominancia, la edad y variables antropométricas. Haciendo uso de un dinamómetro Jamar y con la participación de 681 sujetos (48,9 % F y 51.1 % M) aparentemente sanos de la Ciudad de Bogotá (Colombia), quienes desempeñaban diferentes actividades ocupacionales, se encontró que las fuerzas PP y KP fueron significativamente más altas en los hombres que en las mujeres tanto en la mano no dominante (8.27 Kgf Vs 6.0 Kgf) como en la mano dominante (8.57 Kgf Vs 6.27 Kgf). Se propusieron modelos predictivos que definieron como variables principales la edad, espesor, circunferencia y circunferencia máxima de la mano. En el género femenino se estableció como variable primordial la edad, mientras que en el masculino en dos modelos se define la circunferencia de la mano y en otros dos la circunferencia máxima de la mano.
Kicking and cutting skills in soccer are clearly unilateral, require asymmetrical motor patterns and lead to the development of asymmetrical adaptations in the musculoskeletal function of the lower ...limbs. Assuming that these adaptations constitute a chronicity-dependent process, this study examined the effects of professional training age (PTA) on the composite strength profile of the knee and ankle joint in soccer players. One hundred soccer players (n=100) with short (5-7 years), intermediate (8-10 years) and long (>11 years) PTA were tested bilaterally for isokinetic concentric and eccentric strength of the knee and ankle muscles. Knee flexion-extension was tested concentrically at 60°, 180° and 300 °/sec and eccentrically at 60° and 180 °/sec. Ankle dorsal and plantar flexions were tested at 60 °/sec for both the concentric and eccentric mode of action. Bilaterally averaged muscle strength (R+L)/2 increased significantly from short training age to intermediate and stabilized afterwards. These strength adaptations were mainly observed at the concentric function of knee extensors at 60°/sec (p = 0. 023), knee flexors at 60°/sec (p = 0.042) and 180°/sec (p = 0.036), and ankle plantar flexors at 60o/sec (p = 0.044). A linear trend of increase in isokinetic strength with PTA level was observed for the eccentric strength of knee flexors at 60°/sec (p = 0.02) and 180°/sec (p = 0.03). Directional (R/L) asymmetries decreased with PTA, with this being mainly expressed in the concentric function of knee flexors at 180°/sec (p = 0.04) and at 300 °/sec (p = 0.03). These findings confirm the hypothesis of asymmetry in the strength adaptations that take place at the knee and ankle joint of soccer players mainly along with short and intermediate PTA. Players with a longer PTA seem to adopt a more balanced use of their lower extremities to cope with previously developed musculoskeletal asymmetries and possibly reduce injury risk. This has certain implications regarding proper training and injury prevention in relation to professional experience in soccer. Key pointsMuscle strength increased from the low (5-7 years) to the intermediate professional training age (8-10 years) and stabilized thereafter.Soccer practicing and competition at the professional level induces critical strength adaptations (asymmetries) regarding the function of the knee and ankle musculature.Soccer players with long professional training age showed a tendency for lower isokinetic strength asymmetries than players with intermediate and short professional training age.
PDF
