Rate Of Force Development Measures Research Articles

Optimizing isometric midthigh pull testing protocols: impact on peak force and rate of force development and their association with jump performance.

Isometric strength testing is widely applied in sports science. However, we hypothesized that traditional testing procedures with a dual focus on both peak force (PF) and rate of force development (RFD) may compromise the true assessment of early RFD measures and lower the associative value towards vertical jump performance. Therefore, PF and RFD were assessed for 47 active participants (24 females, 23 males) with a traditional isometric midthigh pull (IMTP) protocol ("push as hard and fast as possible" over 4 s) and an RFD-specific protocol ("push as fast as possible" over 2 s). IMTP measures were compared to squat (SJ), countermovement (CMJ) and drop-jump (DJ) performance. The RFD-specific protocol provided higher RFD (P<0.05) for time domains up to 100 ms but lower PF (P<0.001). Independent of protocol, SJ and CMJ performance displayed significant, but low-to-moderate correlations with all RFD measures (r=0.30-0.52) as well as PF (r=0.44), whereas DJ did not show any correlation. In conclusion, an RFD-specific protocol appears relevant for the assessment of RFD in the time domain up to 100 ms. However, the observed associations between RFD/PF measures and vertical jump performance remained low-to-moderate independent of the IMTP test protocol.

Evaluation of orofacial force-related measures using a novel measuring device: explanation of associations with speech rate in dysarthria

ABSTRACT Background The aim of this study was to examine the potential associations between orofacial force-related measures and speech rate in matched groups of 23 adults with dysarthria, and 69 healthy adults. Research design and methods A novel piezoresistive sensor-based device was utilized to obtain the orofacial maximum forces (OMFs) and rate of force development (RFD) measures. The study computed alternating motion rates (AMRs), sequential motion rates (SMRs), and articulation rate (AR) for all participants. The analysis included between-group comparisons and correlation analyses. The study also examined the reliability of the OMFs and RFD measures. Results Individuals with dysarthria exhibited significantly slower speech rates (approximately 41.89% to 56.53% slower) compared to the control group. Except for a few exceptions in the jaw, the dysarthria group demonstrated significantly lower OMFs and RFD measures. The correlation analysis revealed that OMFs were weakly to moderately correlated (r = .488–.674) and RFD measures were very weak to moderately correlated (r = .047–.578) with speech rate measures. Conclusions The findings suggest that reduced OMFs and RFD measures may contribute to the slowed speech rate observed in adults with dysarthria. The study also highlights that OMFs are significantly more reliable (day-to-day) than RFD measures.

Identifying Reliable and Relatable Force-Time Metrics in Athletes-Considerations for the Isometric Mid-Thigh Pull and Countermovement Jump.

The purpose of this study was to evaluate intrasession reliability of countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) force–time characteristics, as well as relationships between CMJ and IMTP metrics. Division I sport and club athletes (n = 112) completed two maximal effort CMJ and IMTP trials, in that order, on force plates. Relative and absolute reliability were assessed using intraclass correlation coefficients (ICCs) > 0.80 and coefficients of variation (CVs) < 10%. Intrasession reliability was acceptable for the majority of the CMJ force–time metrics except for concentric rate of force development (RFD), eccentric impulse and RFD, and lower limb stiffness. The IMTP’s time to peak force, instantaneous force at 150 ms, instantaneous net force, and RFD measures were not reliable. Statistically significant weak to moderate relationships (r = 0.20–0.46) existed between allometrically scaled CMJ and IMTP metrics, with the exception of CMJ eccentric mean power not being related with IMTP performances. A majority of CMJ and IMTP metrics met acceptable reliability standards, except RFD measures which should be used with caution. Provided CMJs and IMTPs are indicative of distinct physical fitness capabilities, it is suggested to monitor athlete performance in both tests via changes in those variables that demonstrate the greatest degree of reliability.

Isometric mid-thigh pull force-time characteristics: A good indicator of running performance

Objectives: The relationship between force-time characteristics obtained from isometric mid-thigh pull (IMTP) and endurance running performance has not been studied. The purpose of this study was to investigate the relationships between force-time characteristics obtained from IMTP with indicators of endurance running performance. Design and Methods: Participants attended a familiarisation session to be familiarised with all testing protocols. Subsequently, they completed the IMTP and a 2.4-km run time trial (2.4-kmTT) on the first testing session. Post 48-72 h of the first session, they then performed a running economy (RE) test at 12 km.h‒1 and graded exercise test on the second testing session. Results: Significant inverse correlations between all IMTP measures and 2.4kmTT was observed (r = -0.53 to -0.78, p < 0.01). Similarly, all IMTP measures were significantly correlated to maximal aerobic speed (r = 0.38 to 0.66, p < 0.05) except Force at 150 ms. There were significant correlations between IMTP peak force, net peak force and rate of force development (0-150 ms) with lower limb stiffness (r = 0.41 to 0.49, p < 0.05). Force at 100 ms and all rate of force development measures were significantly correlated to RE (r = -0.44 to -0.68, p < 0.05). Conclusion: Findings showed that measures obtained from IMTP are good indicators of endurance running performance and can provide insights into the force generating capability required by endurance runners. In addition, the significant correlations between strength measures and running performance suggest that muscular strength may be an important determinant of running performance.

Utility of a Shortened Isometric Midthigh Pull Protocol for Assessing Rapid Force Production in Athletes.

Suarez, DG, Carroll, KM, Slaton, JA, Rochau, KG, Davis, MW, and Stone, MH. Utility of a shortened isometric midthigh pull protocol for assessing rapid force production in athletes. J Strength Cond Res 36(7): 1819-1825, 2022-The purpose of this investigation was to determine the magnitude of difference, reliability, and relationship to performance of a shortened isometric midthigh pull (IMTP) protocol. Fourteen strength-trained men (age: 26.8 ± 5.0 years, height: 176.3 ± 6.9 cm, body mass: 86.8 ± 13.9 kg, and training age: 8.5 ± 6.9 years) performed 1-second (SHORT) and traditional (TRAD) IMTP protocols during consecutive weeks. Peak force (PF), instantaneous force (90 & 200 ms), rate of force development (RFD) (0-90 ms & 0-200 ms), and impulse (0-90 ms & 0-200 ms) from each protocol were collected. Paired samples t test and Hedge's g were calculated to determine the magnitude of difference in each variable between protocols. Within-session and between-session reliability was assessed with intraclass correlation coefficient, coefficient of variation, and 95% confidence intervals. Static jumps were performed to compare relationships of the IMTP variables from each protocol with jumping performance. There was no statistically significant (p > 0.05) difference in PF between the protocols (p = 0.345; g = -0.07). All early force-time variables were significantly higher in the SHORT protocol (p = <0.001-0.018; g = 0.38-0.79). The SHORT protocol resulted in more reliable RFD measures within-session. Correlations with jumping performance were mostly similar between protocols (r = 0.253-0.660). The SHORT IMTP protocol resulted in comparable PF values and considerably higher early force-time characteristics despite a restrained time to produce force and shorter rest. The SHORT protocol allows for an accurate assessment of rapid force-generating abilities while necessitating shorter collection periods than typical IMTP protocols.

Sit-to-Stand Kinetics and Correlates of Performance in Young and Older Males

PurposeTo compare sit-to-stand (STS) kinetics in young (YM) and older (OM) males and determine correlates of STS performance. MethodsYM (n = 15, age = 20.7 ± 2.2 yrs) and OM (n = 15, age = 71.6 ± 3.9 yrs) performed a single STS task as quickly as possible on a force plate and the vertical ground reaction force (VGRF) signal was analyzed. Peak VGRF, as well as peak (100 ms rolling average), early (minimum VGRF to 50% peak VGRF), late (50% peak VGRF to peak VGRF), and overall (minimum VGRF to peak VGRF) rate of force development (RFD) were calculated. Power (absolute and relative) and velocity parameters as well as rate of electromyography rise (RER) were also obtained. ResultsSTS time, average power, early RFD, and lower limb lean mass were similar between groups (p > 0.05). All other power, velocity, RFD, and RER measures were lower in OM (p < 0.05; d = 0.41-2.19). Peak VGRF and all RFD measures, except late RFD, were strongly correlated with STS performance in OM, while peak VGRF and peak RFD were only moderately correlated with performance in YM. ConclusionsMost kinetic variables, except absolute average power, were diminished in OM, and there was a preferential decrease in late RFD compared to early RFD. Peak VGRF and RFD exhibited stronger correlations with STS time and power in OM compared to YM, and early RFD appears to be more influential for STS performance than late RFD. These findings may be useful for practitioners/clinicians involved in designing interventions aimed at optimizing STS performance in older adults.

Validity and Reliability of the Isometric Prone Bench Pull Test.

Isometric strength tests are gaining popularity in recent years. However, no study has validated any isometric strength tests to assess upper body pulling ability. The aim of this study was to investigate the validity and reliability of isometric prone bench pull. Twenty-three resistance trained athletes (age: 26±4 years, height: 1.75±0.07 m, body mass: 78.6±11.5 kg) were required to perform prone bench pull 1 repetition maximum and isometric prone bench pull tests during the familiarization and actual testing sessions. Isometric prone bench pull was performed at 90° and 120° elbow angles. Peak force and rate of force development measures were highly reliable with intra-correlation coefficient between 0.881-0.987. Peak force obtained from isometric prone bench pull at both elbow angles showed large correlations to prone bench pull 1 repetition maximum (r=0.833-0.858, p<0.01). Linear regression equations to predict 1RM performance from isometric prone bench pull peak force produced an estimated 1RM with a standard error of only 3-6% of the average prone bench pull 1 repetition maximum. The current findings show that isometric prone bench pull is a reliable test and can be used to predict prone bench pull performance.

The Inter-Session Reliability of Isometric Force-Time Variables and the Effects of Filtering and Starting Force.

The purposes of the present study were to assess the inter-session reliability of force-time variables recorded during isometric back squats and also to assess the effects of applying a filter to the data prior to analysis and assess the effects of different starting force thresholds on the force-time variables. Eleven resistance trained men (age: 22.5 ± 1.9 years; body mass: 90.3 ± 13.5 kg) attended two sessions where they performed isometric squats on force plates allowing the determination of force-time variables of maximal isometric force (Fmax) and different measures of the rate of force development (RFD). The force-time variables were calculated from both raw and filtered force signals. The start of the force application was determined using force thresholds of 1% or 5% of body mass (BM). Inter-session reliability for the force-time measures was assessed by calculating the intraclass correlation coefficient (ICC) and the coefficient of variation (CV) of the measures. The ICC and CV ranged from 0.03 to 0.96 and 4.6 to 168%, respectively. The application of the filter significantly reduced Fmax and peak RFD (p < 0.004) and increased the reliability of the peak RFD. The use of the 5% BM threshold increased the magnitude of many of the RFD measures (p < 0.004) and resulted in slight improvements in the reliability of these measures although the resulting temporal shift in the force-time signal would preclude accurate assessment of the early phase of the RFD (< 100 ms). The use of a 1% BM starting force threshold without a filter is recommended when using the isometric back squat protocol presented here. Furthermore, the RFD calculated within specific time intervals is recommended

Multi-joint rate of force development testing protocol affects reliability and the smallest detectible difference

ABSTRACTIsometric tests have been used to assess rate of force development (RFD), however variation in testing methodologies are known to affect performance outcomes. The aim of this study was to assess the RFD in the isometric squat (ISqT) using two test protocols and two testing angles. Eleven participants (age: 26.8 ± 4.5 years, strength training experience: 7.1 ± 3.03 years) completed test and retest sessions one week apart, whereby two test protocols with respect to duration and instructions were compared. Isometric peak force (ISqTpeak) and isometric explosive force (ISqTexp) tests were assessed at two joint angles (knee flexion angle 100° and 125°). Force-time traces were sampled and subsequently analysed for RFD measures. Average and instantaneous RFD variables did not meet reliability minimum criteria in ISqTpeak at 100° or 125°. The ISqTexp test at 100° met reliability criteria in the RFD 0–200 and 0–250ms variables. The ISqTexp test at 125° met reliability criteria in the RFD 0–150, 0–200 and 0–250ms variables. Force-time characteristics were optimized at the higher knee joint angle. Average and instantaneous RFD measures obtained using a traditional peak force test do not meet basic reliability criteria. Researchers assessing multi-joint RFD should employ the explosive RFD test protocol as opposed to the traditional isometric peak force protocol.

The efficacy of periodised resistance training on neuromuscular adaptation in older adults.

This study compared the effect of periodised versus non-periodised (NP) resistance training on neuromuscular adaptions in older adults. Forty-one apparently healthy untrained older adults (female=21, male=20; 70.9±5.1 years; 166.3±8.2cm; 72.9±13.4kg) were recruited and randomly stratified to an NP, block periodised (BP), or daily undulating periodised (DUP) training group. Outcome measures were assessed at baseline and following a 22-week resistance training intervention (3 day week-1), including: muscle cross-sectional area (CSA), vertical jump performance, isometric and isokinetic peak torque, isometric rate of force development (RFD), and muscle activation. Thirty-three participants satisfied all study requirements and were included in analyses (female=17, male=16; 71.3±5.4 years; 166.3±8.5cm; 72.5±13.7kg). Block periodisation, DUP, and NP resistance training induced statistically significant improvements in muscle CSA, vertical jump peak velocity, peak power and jump height, and peak isometric and isokinetic torque of the knee extensors at 60 and 180° s-1, with no between-group differences. Muscle activity and absolute RFD measures were statistically unchanged following resistance training across the entire cohort. Periodised resistance training, specifically BP and DUP, and NP resistance training are equally effective for promoting increases in muscular hypertrophy, strength, and power among untrained older adults. Consequently, periodisation strategies are not essential for optimising neuromuscular adaptations during the initial stages of resistance training in the aging population.

Quadriceps rate of force development affects gait and function in people with knee osteoarthritis

Quadriceps weakness exists in people with knee osteoarthritis (OA), but other muscle factors like rate of force development (RFD) may also be affected by knee OA. The purpose of this study was to determine if people with knee OA have deficits in quadriceps RFD, determine if quadriceps RFD would improve predicting knee joint power absorption and generation during free and fast walking, and determine if RFD would improve predicting functional outcomes. 26 subjects with knee OA and 23 healthy control subjects performed maximal voluntary isometric strength (MVIC) and RFD measures of the quadriceps. Subjects also underwent a 3-D motion analysis of both self-selected free and self-selected fast walking speeds. Joint kinetics were calculated from inverse dynamics. RFD was not different by group (p = 0.763), however, the OA subjects generated the highest peak RFD at a lower % MVIC (p = 0.008). Controls walked significantly faster at both free and fast walking speeds (p = 0.001, p = 0.029). Knee angles at heel strike and peak knee extension were lower (p = 0.004, p = 0.027) in the OA group. During fast walking knee power generation was higher in controls (p = 0.028). MVIC and force of highest peak RFD predicted KOOS-ADL score in the OA subjects, but only MVIC predicted stair climbing time. The submaximal force at which peak RFD occurs plays a significant role in knee joint power as well as functional measures in the OA subjects, providing further evidence that factors other than maximal strength are also important in people with knee OA.

A New Progression Scale for Common Lower-Limb Rehabilitation Tasks

The treatment of most injuries tends to have similar goals: to minimize initial pain and swelling, restore full range of motion, and return to full strength. One of the key problems is the gap between the traditional rehabilitation modalities and progression to normal locomotive and athletic activities. Closed kinetic chain exercises are a common feature of rehabilitation programs, yet progression of these exercises in a rehabilitation setting has traditionally been based on anecdotal advice, and there is a shortage of empirical evidence. The aim of this study is to use ground reaction force measures to guide progression of closed kinetic chain rehabilitation exercises for active individuals recovering from lower extremity injury. Twenty-four injury-free participants carried out 10 different movements including jumps, squats, and locomotive tasks. Force data collected via a Kistler force platform were used to quantify peak vertical force (Fz), peak vertical force relative to body weight (Fz/BW), and rate of force development (RFD). A Vicon motion analysis system provided kinematic data. There were significant interactions of task and peak Fz, task and peak Fz/BW, and task and RFD. For all force measures, the majority of tasks were significantly different from one another. The effect of kinematic variability was evaluated using the Pearson Correlation coefficient. A clear progression of exercises was seen in both peak Fz and peak Fz/BW, whereas RFD measures showed 3 distinct groups. Combining the data from the measures leads to the grouping the exercises into early, mid, late, and final stages of rehabilitation. We suggest that practitioners use this ranking to prescribe appropriate exercises for particular stages of rehabilitation.