Rapid Torque Research Articles

Direct Torque Control Space Vector Modulation for Induction Motor Driven by Matrix Converter

This study proposes enhancing induction motor (IM) drive systems by developing a DTC-MC with SVPWM integration to reduce ripple. DTC-MC is effective for precise torque control in AC drives, offering high control accuracy by isolating stator flux and torque. The method excels in sensor-less speed control, maintaining unity input power factor at low speeds, and constant switching frequency for rapid torque adjustments. Combining DTC-MC with SVPWM improves simplicity, dynamic behavior, and torque response. The DTC-SVM approach further refines the torque response by correcting flux and torque discrepancies. MATLAB/SIMULINK simulations validated the approach, showing a robust dynamic response and significantly reduced motor torque ripple and control of speed.

Changes In Rapid Torque Development Following Different Resistance Training Modalities To Fatigue

Changes In Rapid Torque Development Following Different Resistance Training Modalities To Fatigue

Central and peripheral neuromuscular fatigue following ramp and rapid maximal voluntary isometric contractions.

Maximal voluntary isometric contractions (MVICs) as a fatiguing modality have been widely studied, but little attention has been given to the influence of the rate of torque development. Given the established differences in motor command and neuromuscular activation between ramp and rapid MIVCs, it is likely performance fatigue differs as well as the underlying physiological mechanisms. To compare responses for rapid and maximal torque following ramp and rapid MVICs, and the corresponding neuromuscular and corticospinal alterations. On separate visits, twelve healthy males (22.8 ± 2.5years) performed fatiguing intermittent MVICs of the knee extensors with either 2s (RAMP) or explosive (RAPID) ramp-ups until a 50% reduction in peak torque was achieved. Before and after each condition, maximal and rapid torque measures were determined from an MVIC. Additionally, peripheral (twitch parameters) and central (voluntary activation) fatigue, as well as rapid muscle activation, and cortical-evoked twitch and electromyographic responses were recorded. Maximal and late-phase rapid torque measures (p ≤ 0.001; = 0.635-0.904) were reduced similarly, but early rapid torque capacity (0-50ms) (p = 0.003; d = 1.11 vs. p = 0.054; d = 0.62) and rapid muscle activation (p = 0.008; d = 1.07 vs. p = 0.875; d = 0.06) decreased more after RAMP. Changes in peripheral fatigue, as indicated by singlet and doublet contractile parameters (p < 0.001 for all; = 0.752-0.859), and nerve-evoked voluntary activation (p < 0.001; 0.660) were similar between conditions. Corticospinal inhibition (via silent period) was only increased after RAPID (p = 0.007; d = 0.94 vs. p = 0.753; d = 0.09), whereas corticospinal voluntary activation and excitability were unchanged. Ramp, fatiguing MVICs impaired early rapid torque capacity more than rapid MVICs, and this was accompanied by decrements in rapid muscle activation. Responses for peripheral and central fatigue (nerve and cortical stimulation) were largely similar between conditions, except that rapid MVICs increased corticospinal inhibition.

Age-related effects of neuromuscular fatigue and acute recovery responses on maximal and rapid torque measures of the leg extensors and flexors.

To examine the effects of neuromuscular fatigue and recovery on maximal and rapid torque characteristics in young and old men for the leg extensors and flexors. Twenty-one young (age = 24.8years) and 19 old (72.1years) men performed maximal voluntary contractions (MVCs) before and at 0, 7, 15, and 30min following an intermittent submaximal fatigue task. Outcome measures included endurance time, maximal (peak torque; PT) and rapid (absolute and normalized rate of torque development; RTD and nRTD) torque characteristics. The old men had greater endurance times than the young men. Differential recovery patterns were observed for PT, and early and late RTD phases between the leg extensor and flexor musclegroups such that the early rapid torque variables and the flexors demonstrated slower recovery compared to later rapid torque variables and the extensors. The normalized RTD variables were reduced less after the fatigue task and differential muscle and age effects were observed where the flexors were reduced more at the early phase (nRTD1/6) compared to the extensors, however, for the later phase (nRTD2/3) the young men exhibited a greater reduction compared to the old men. Dissimilar fatigue recovery patterns across different phases of RTD, lower limb muscles, and age groups may have important fatigue-related performance and injury risk implications across the adult lifespan.

A Comparative Study on the Performance of the Induction Motor with Fuzzy-Based Power Converters

This study investigates the influence of load conditions on grid voltage stability and the performance of a proposed compensator, encompassing a 1.5 hp 4-pole induction motor (IM) exposed to grid voltage disturbances. Through rigorous grid current analysis, our research demonstrates the effective mitigation of total harmonic distortion (THD) without necessitating passive filters. The comprehensive study covers multiple facets, including control strategy optimization, fine-tuning of control parameters, component ratings, output voltage analysis, operating principles, pulse width modulation, and the integral role of the fuzzy logic controller. Specifically, it underscores the significant impact of a Predictive Torque Control-based Diode Clamped Inverter in enhancing the dynamic and steady-state performance of the IM. The research delves into traditional PTC control methods and advanced techniques, such as fuzzy and evolutionary control, addressing the persistent challenge of reducing torque ripple under varying load conditions. By implementing model prediction control-based DCI, our method achieves rapid torque response without compromising the motor’s stator characteristics. Utilizing MATLAB’s environmental package, we thoroughly evaluate motor performance across diverse scenarios, encompassing stable, and rapid load changes. Despite inherent winding impedance challenges, our proposed approach consistently delivers satisfactory output responses, contributing to a more efficient, and resilient IM performance under diverse operating conditions.

Effects of Acute Sleep Deprivation on the Sequential Rate of Torque Development throughout the Force-Time Curve.

Objective The impact of sleep deprivation on the physiological determinants of explosive torque production remains poorly understood. We aimed at determining the acute effects of 24 hours of sleep deprivation on the sequential rate of torque development (RTD) obtained during plantar flexion through maximum voluntary isometric contraction (MVIC). Materials and Methods The study included 14 healthy-young adults (8 men and 6 women). The participants visited the laboratory on 2 different occasions: without and with 24 hours of sleep deprivation. In each session, the subjects were tested for RTD of the plantar flexors with concomitant recordings of the electromyographic (EMG) amplitude of the soleus over the following time intervals: 0 to 30, 30 to 50, 50 to 100, and 100 to 150 ms. Results Sleep deprivation did not affect peak RTD (without sleep deprivation: 283.3 ± 111.6 N.m.s -1 versus with sleep deprivation: 294.9 ± 99.2 N.m.s -1 ; p > 0.05) of plantar flexion. The sequential values of RTD, as well as the normalized amplitude of the soleus EMG, remained similar between both conditions (p > 0.05). Discussion In conclusion, we found that 24 hours of sleep deprivation do not affect muscle activation, nor explosive torque production throughout the torque-time curve. Thus, exercise performance and daily functionality in tasks involving rapid torque development might remain well preserved after 24 hours of acute sleep deprivation.

Performance Prediction of D.C. Motor Fed From Half-Controlled Bridge Rectifier

Controlled rectification is the process of obtaining a controlled output DC voltage from a constant AC voltage. This can be used in the speed control of the DC motor to provide rapid torque control and a quick starting response. In this work, a three-phase half-controlled bridge rectifier has been used. The average output DC voltage varies smoothly by varying the firing angle (α). Different methods of analysis such as state-space and Fourier-series, are used to obtain the performance of the DC motor fed from the bridge-rectifier supply. However, these methods do not deal with the prediction of the discontinuous conduction phenomenon which occurs during the operation of the DC motor with a variation of delay angle. This paper deals with the prediction of performance characteristics during the operation of the DC motor fed by a 3-phase half-controlled bridge rectifier, including the transient as well as steady-state operation with a variation of delay angle as well as application of load torque at starting.

The effects of regional quadriceps architecture on angle-specific rapid force expression.

Evaluating anatomical contributions to performance can increase understanding of muscle mechanics and guide physical preparation. While the impact of anatomy on muscular performance is well studied, the effects of regional quadriceps architecture on rapid torque or force expression are less clear. Regional (proximal, middle, and distal) quadriceps (vastus lateralis, rectus femoris, and vastus intermedius) thickness (MT), pennation angle (PA), and fascicle length (FL) of 24 males (48 limbs) were assessed via ultrasonography. Participants performed maximal isometric knee extensions at 40°, 70°, and 100° of knee flexion to evaluate rate of force development from 0 to 200ms (RFD0-200). Measurements were repeated on three occasions with the greatest RFD0-200 and mean muscle architecture measures used for analysis. Linear regression models predicting angle-specific RFD0-200 from regional anatomy provided adjusted correlations (√adjR2) with bootstrapped compatibility limits. Mid-rectus femoris MT (√adjR2=0.41-0.51) and proximal vastus lateralis FL (√adjR2=0.42-0.48) were the best single predictors of RFD0-200, and the only measures to reach precision with 99% compatibility limits. Small simple correlations were found across all regions and joint angles between RFD0-200 and vastus lateralis MT (√adjR2=0.28±0.13; mean±SD), vastus lateralis FL (√adjR2=0.33±0.10), rectus femoris MT (√adjR2=0.38±0.10), and lateral vastus intermedius MT (√adjR2=0.24±0.10). Between-correlation comparisons are reported within the article. Researchers should measure mid-region rectus femoris MT and vastus lateralis FL to efficiently and robustly evaluate potential anatomical contributions to rapid knee extension force changes, with distal and proximal measurements providing little additional value. However, correlations were generally small to moderate, suggesting that neurological factors may be critical in rapid force expression.

Voluntary torque production is unaffected by changes in local thermal sensation during normothermia and hyperthermia.

What is the central question of this study? Hyperthermia reduces the human capacity to produce muscular force, which is associated with decreased neural drive: does mitigating a reduction in neural drive by altering localised thermal sensation help to preserve voluntary force output? What is the main finding and its importance? Altering thermal sensation by cooling and heating the head independent of core temperature did not change neural drive or benefit voluntary force production. Head cooling did slow the rate of rise in core temperature during heating, which may have practical applications in passive settings. This study investigated altered local head and neck thermal sensation on maximal and rapid torque production during voluntary contractions. Nine participants completed four visits in two environmental conditions: at rectal temperatures ∼39.5°C in hot (HOT; ∼50°C, ∼39% relative humidity) and ∼37°C in thermoneutral (NEU; ∼22°C, ∼46% relative humidity) conditions. Local thermal sensation was manipulated by heating in thermoneutral conditions and cooling in hot conditions. Evoked twitches and octets were delivered at rest. Maximum voluntary torque (MVT), normalised surface electromyography (EMG) and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions of the knee extensors. Rate of torque development (RTD) and EMG were measured during rapid voluntary contractions. MVT (P=0.463) and RTD (P=0.061) were similar between environmental conditions despite reduced VA (-6%; P=0.047) and EMG at MVT (-31%; P=0.019). EMG in the rapid voluntary contractions was also lower in HOT versus NEU during the initial 100ms (-24%; P=0.035) and 150ms (-26%; P=0.035). Evoked twitch (+70%; P<0.001) and octet (+27%; P<0.001) RTD during the initial 50ms were greater in the HOT compared to NEU conditions, in addition to a faster relaxation rate of the muscle (-33%; P<0.001). In conclusion, hyperthermia reduced neural drive without affecting voluntary torque, likely due to the compensatory effects of improved intrinsic contractile function and faster contraction and relaxation rates of the knee extensors. Changes in local thermal perception of the head and neck whilst hyperthermic or normothermic did not affect voluntary torque.

Fuzzy-Logic Controller for Smart Drives

The fuzzy logic controller, or FLC, is a sort of artificial intelligence (AI) control that provides improved signal waveforms at the output and decreases oscillations when compared to traditional control (such as output speed variation, torque variation, and current variation for the three phases). This paper shows two FLC scenarios, one with 25 rules and the other with 49 rules, for PMSMs with an external permanent magnet (Ld=Lq). The FLC can be implemented in real time since it is designed to be computationally light. Permanent magnet synchronous machines (PMSMs) with high torque density, low losses-to-torque ratio, high power factor, and rapid torque and speed responsiveness offer a broad range of novel application possibilities.

Effects of 6-weeks of detraining on functional capacity and rapid torque production in older women

Mat Pilates has become an attractive alternative exercise among older women, however, despite knowing the importance of regular exercise, interrupting training is a common issue in this population. The aim of the current study was to evaluate the effects of 6-weeks of detraining after a period of 12-weeks of training with Mat Pilates on the functional capacity and neuromuscular performance of the knee extensor muscles in older women. Ten older women (62.6 ± 2.6 years; 1.57 ± 0.05 m height; 69.3 ± 9.2 kg; 27.8 kg/m2 body mass index) volunteered to participate in this study. The study was divided into three periods: a 4-week control period, followed by 12 weeks of Mat Pilates intervention, and a 6-week detraining period. During the intervention, the results showed significant improvements in functional capacity tests (time up and go, time up stairs, time down stairs, and chair sit-and-reach), rate of torque development, and impulse (p < 0.05). After the detraining period, a decrease was observed in the chair sit-and-reach test (p < 0.05) and contractile impulse at intervals 0–30 and 0–50 ms (p < 0.05). We conclude that a 6-week detraining period after a Mat Pilates training protocol was sufficient to cause declines in the chair sit-and-reach test and in the contractile impulse of the knee extensors in the early phase of the torque-time curve (0–30 and 0–50 ms), but not in the other functional capacity tests and neuromuscular parameters evaluated.

Test-Retest Reliability of Plantar Flexion Torque Generation During a Functional Knee Extended Position in Older and Younger Men.

Measuring ankle torque is of paramount importance. This study compared the test-retest reliability of the plantar flexion torque-generating capacity between older and younger men. Twenty-one older (68 ± 6years) and 22 younger (25 ± 5years) men were tested twice for maximal isometric plantar flexion. Peak torque (PT), rate of torque development, and contractile impulses (CI) were obtained from 0 to 50ms (rate of torque development0-50; CI0-50) and from 100 to 200ms (rate of torque development100-200; CI100-200). Typical error as the coefficient of variation (CVTE) and intraclass correlation coefficient were used to assess test-retest reliability. Student's t test was applied to investigate systematic errors. The CVTE ratio was used for between-group comparisons. Only PT demonstrated acceptable reliability (intraclass correlation coefficient ≥ .75 and CV ≤ 10%). Older men demonstrated greater CVTE than younger men for PT (ratio = 2.24), but lesser for rapid torque (ratio ≤ 0.84). Younger men demonstrated systematic error for PT (6.5%) and CI100-200 (-8.9%). In conclusion, older men demonstrated greater variability for maximal torque output, but lesser for rapid torque.

Contralateral training effects of low-intensity blood-flow restricted and high-intensity unilateral resistance training.

Determine whether unilateral low-intensity blood-flow restricted (LIBFR) exercise is as effective as high-intensity (HI) resistance training for improving contralateral muscle strength. Thirty healthy adults (20-30 years) were randomly allocated to the following dynamic plantar-flexion training interventions: HI [75% of one-repetition maximum (1RM), 4 sets, 10 reps] and LIBFR [20% of 1RM, 4 sets, 30 + 15 + 15 + 15 reps]. Evoked V-wave and H-reflex recruitment curves, as well as maximal voluntary contraction (MVC) and panoramic ultrasound assessments of the trained and untrained soleus muscles were obtained pre-training, post-4 weeks of training and post-4 weeks of detraining. Both interventions failed to increase contralateral MVC and muscle cross-sectional area (CSA). Yet, contralateral rate of torque development (RTD) was enhanced by both regimens (12-26%) and this was accompanied by heightened soleus EMG within the first milliseconds of the rising torque-time curve (14-22%; p < 0.05). These improvements were dissipated after detraining. Contralateral adaptations were not accompanied by changes in V-wave or H-reflex excitability. Conversely, LIBFR and HI elicited a similar magnitude of ipsilateral increase in MVC, RTD and CSA post-training (10-18%). Improvements in V-wave amplitude and soleus EMG were limited to the trained leg assigned to LIBFR training (p < 0.05). While gains in strength and CSA remained preserved post-4 weeks of detraining, this did not occur with RTD. Since gains in RTD were similar between interventions, our findings indicate that both training regimens can be used interchangeably for improving contralateral rapid torque production. Ultimately, this may be beneficial in circumstances of limb immobilization after injury or surgery.

Age-Related Differences in Hip Flexion Maximal and Rapid Strength and Rectus Femoris Muscle Size and Composition.

This study aimed to examine the effects of age on hip flexion maximal and rapid strength and rectus femoris (RF) muscle size and composition in men. Fifteen young (25 [3]y) and 15 older (73 [4]y) men performed isometric hip flexion contractions to examine peak torque and absolute and normalized rate of torque development (RTD) at time intervals of 0 to 100 and 100 to 200milliseconds. Ultrasonography was used to examine RF muscle cross-sectional area and echo intensity. Peak torque, absolute RTD at 0 to 100milliseconds, and absolute and normalized RTD at 100 to 200milliseconds were significantly lower (P = .004-.045) in the old compared with the young men. The older men exhibited lower cross-sectional area (P = .015) and higher echo intensity (P = .007) than the young men. Moreover, there were positive relationships between cross-sectional area and absolute RTD at 0 to 100milliseconds (r = .400) and absolute RTD at 100 to 200milliseconds (r = .450) and negative relationships between echo intensity and absolute RTD at 100 to 200milliseconds (r = -.457) and normalized RTD at 100 to 200milliseconds (r = -.373). These findings indicate that hip flexion maximal and rapid strength and RF muscle size and composition decrease in old age. The relationships observed between ultrasound-derived RF parameters and measurements of RTD suggest that these age-related declines in muscle size and composition may be relevant to hip flexion rapid torque production.

Progressive hyperthermia elicits distinct responses in maximum and rapid torque production

ObjectivesTo investigate the effect of progressive whole-body hyperthermia on maximal, and rapid voluntary torque production, and their neuromuscular determinants. DesignRepeated measures, randomised. MethodsNine participants performed sets of neuromuscular assessments in HOT conditions (∼50°C, ∼35% relative humidity) at rectal temperatures (Tre) of 37, 38.5 and 39.5°C and in CON conditions (∼22°C, ∼35% relative humidity) at a Tre of ∼37°C and pre-determined comparative time-points. Electrically evoked twitch (single impulse) and octet (8 impulses at 300Hz) responses were measured at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were measured during 3−5s isometric maximal voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary isometric contractions from rest. ResultsAll neuromuscular variables were unaffected by time in CON. In HOT, MVT, normalised EMG at MVT and VA were lower at 39.5°C compared to 37°C (p<0.05). Early- (0−50ms) and middle- (50−100ms) phase voluntary RTD were unaffected by increased Tre (p>0.05), despite lower normalised EMG at Tre 39.5°C (p<0.05) in rapid contractions. In contrast, late-phase (100−150ms) voluntary RTD was lower at 38.5°C and 39.5°C compared to 37°C (p<0.05) in HOT. Evoked twitch and octet RTD increased with increased Tre (p<0.05). ConclusionsHyperthermia reduced late-phase voluntary RTD, likely due to reduced neural drive and the reduction in MVT. In contrast, early- and middle-phase voluntary RTD were unaffected by hyperthermia, likely due to the conflicting effects of reduced neural drive but faster intrinsic contractile properties.

Rapid Torque Rising of PMSM by Directly Chasing Rotating Flux Linkage Vector

The principle of permanent magnet synchronous motor (PMSM) torque control could be seen as driving the stator flux linkage vector to chase a rotating reference by the voltage vectors. An increase in the magnitude of the stator flux linkage vector limits the ability of the voltage vector to vary the torque angle and the torque. In most control strategies, simultaneously increasing that magnitude and the torque angle slows down the PMSM torque response. In this article, a new method to quicken the PMSM torque rising is proposed. The key idea is to predict an almost static flux linkage vector as the target and find a shortcut consisting of the voltage vector sequence during torque tracking to catch up with the rotating reference rapidly. Then, the torque rising can be accelerated by first shortening the stator flux linkage vector to quickly rotate it and then lengthening it. A set of comparative experimental results are presented to confirm the validity of this method.

In vivo manipulation of muscle shape and tendinous stiffness affects the human ability to generate torque rapidly.

What is the central question of this study? What are the determinants of muscle belly gearing, and how does it affect the torque rise? What is the main finding and its importance? Change in muscle thickness of the gastrocnemius medialis is related to variations in belly gearing. Belly gearing has a key role in the rise of muscle torque and rate of torque development (RTD). Besides, the increase of tendinous tissue stiffness could increase the torque rise as well, and in turn, the RTD. However, changes in the tendinous tissue stiffness showed no effects on muscle fascicle behaviour, suggesting a possible uncoupling between muscle and tendon mechanical properties. During fixed-end contractions, muscles bulge in thickness and/or width to maintain a constant volume, whereas tendons lengthen over the entire contraction period. These dynamic changes play a key functional role in modulating the generated torque. However, the literature has revealed a limited understanding of in vivo dynamic muscle-tendon changes during rapid contractions. Therefore, this study aimed to investigate the determinants of belly gearing (belly velocity/fascicle velocity) and its effects on rapid torque production during in vivo fixed-end contractions. Twenty healthy males were recruited for the study. Muscle shape and tendon stiffness were manipulated by applying a transverse load (2-10kg) and an ankle rotation manoeuvre, respectively. Ultrafast-ultrasound was employed to quantify medial gastrocnemius architecture during evoked contraction and a dynamometer was used to measure the muscle torque and quantify the rate of torque development (RTD). Torque and RTD diminished by transverse load application, whereas they increased during the ankle rotation manoeuvre. Belly gearing declined with increasing transverse load but was unaffected by tendinous stiffness variations. Alterations in belly gearing were strongly related to variations in muscle thickness throughout any load applied and affected the torque rise rapidly. In contrast, changes in tendinous tissue stiffness affected the torque rise only but did not modify the muscle shape. These data may suggest that concurrent manipulation of the tendinous tissue stiffness and muscle shape does not affect the explosive rise in torque capacity, suggesting a possible uncoupling between mechanical properties of muscle and tendon.

Reconstructed rheometer for direct monitoring of dewatering performance and torque in tailings thickening process

To further clarify the dewatering performance and torque evolution during the tailings thickening process, a self-made rake was connected to a rheometer to monitor the shear stress and torque. The dewatering performance of the total tailings was greatly improved to a solid mass fraction of 75.33% in 240 min. The dewatering process could be divided into three stages: the rapid torque growth period, damping torque growth period, and constant torque thickening zone. The machine restart was found to have a significant effect on the rake torque; it could result in rake blockage. Furthermore, the simultaneous evolution of the torque and solid mass fraction of thickened tailings was analyzed. A relationship between the torque and the solid mass fraction was established, which followed a power function. Both the experimental and theoretical results provide a reference for the deep cone thickener design and operation to enhance the dewatering performance.

Inter-Individual Rapid Force Improvements after Mixed Session and Traditional Periodization in Aging Adults: A Randomized Trial

Different periodization models have been widely used to improve maximum and rapid force in aging adults. However, it is unclear if some specific model can influence the remarkable heterogeneity of responsiveness to rapid torque improvements following resistance training. Compare the effects of mixed session periodization (MSP) and traditional (TP) models on neuromuscular performance and individual responsiveness in aging adults. Twenty-two aging men and women (64.6 ± 5.2 years old; 1.68 ± 0.1 m; 77.8 ± 16.0 kg) completed the intervention period. They were assigned into MSP (n = 11) or TP (n = 11) resistance training for lower limbs. The outcome measures normalized dynamic leg press (5-RM:BM), absolute and normalized knee isometric peak torque (PT and PT:BM) and rate of torque development, and impulse were assessed at baseline and after three blocks of a 9-wk resistance training (3 sessions per week). Thigh leg lean mass was assessed by dual-energy x-ray absorptiometry at baseline and after the intervention. Similar increases were observed for 5-RM:BM (MSP: 28.8% ± 13.5% and TP: 26.4% ± 7.6%, P 0.05). Absolute and normalized RTD remained unchanged throughout intervention (P > 0.05), but both groups improved impulse (MSP: 22.1% ± 25.7% and TP: 12.6% ± 45.2%, P < 0.001). Only MSP responders (n = 5) presented significant time effect for absolute RTD (P < 0.05) and impulse (P < 0.05). Although both periodization protocols increased 5-RM:BM and PT, it was not interchangeable through improvements in RTD even adopting power training session. Furthermore, these results suggest a great inter-individual variability following different periodization models for aging people.

EARLY AND LATE RAPID NEUROMUSCULAR PARAMATERS OF THE PLANTAR FLEXORS IN MIDDLE-AGED AND OLDER MALES

Rapid torque production is important for physical function in older adults. Early and late rapid torque parameters are influenced by different physiological factors; therefore, they may be differentially affected by aging. Few comparisons exist between middle-aged and older adults for early and late rapid torque measures. PURPOSE: To compare early and late rapid torque measures of the plantar flexors (PFs) in middle-aged (MM) and older males (OM). METHODS: Twenty-nine MM (n=14; 45.3±2.6 yrs) and OM (n=15; 65.3±3.2 yrs) performed maximal voluntary isometric contractions of the PFs using a dynamometer. Peak torque (PT), as well as rate of torque development (RTD; Δtorque/Δtime) and impulse (area under the curve) during the early (0-50 ms; RTD0-50, IMP0-50) and late (100-200 ms; RTD100-200, IMP100-200) contraction phases were calculated. Torque at 50 (TQ50), 100 (TQ100), and 200 ms (TQ200) was also obtained. Additionally, RTD and TQ variables were normalized to PT. The onset was 2.5 Nm for all torque variables. Electromyography of the medial gastrocnemius was recorded in order to obtain rate of electromyography rise (RER). RER was calculated as the linear slope of the normalized electromyography signal at 30, 50, and 75 ms from the onset. Independent samples t-tests were used for group comparisons. RESULTS: PT (p=0.105), TQ50 (p=0.156), early (p=0.162), and late (p=0.074) RTD were similar between groups. TQ100 (MM=69.71±16.85 vs. OM=55.99±18.54 Nm·s-1; p=0.046), TQ200 (MM=114.76±26.79 vs. OM=91.56±28.10 Nm·s-1; p=0.031), and IMP100-200 (MM=4.79±1.11 vs. OM=3.83±1.17 Nm·s; p=0.032) were lower in OM. Normalized torque variables showed no differences (p>0.05). RER (p=0.057-0.072) was similar between groups. CONCLUSIONS: Our data indicates that late rapid torque parameters of the PFs were preferentially influenced by age, yet PT appeared to mediate this result. Although not significant, the effect sizes for RER (d=0.69-0.74) may suggest that rapid muscle activation was influential as well.