Passive Torque Research Articles

Discipline-specific adaptation patterns in respiratory and lower limb musculotendinous structures: cyclists vs. basketball players.

This study aimed at assessing how chronic exposure to specific exercise training (high-intensity intervals vs. endurance), comparing experienced basketball-players (BP, N.=16), cyclists (CY, N.=16), and non-specifically trained individuals (CN, N.=16), influences the structural and functional characteristics of both lower limb and respiratory musculotendinous structures. Vastus lateralis, gastrocnemius lateralis, and medialis, diaphragm muscles, as well as patellar tendon and Achilles tendon, were assessed using B-mode ultrasonography. Maximal voluntary isometric and passive torque measurements were conducted in the knee-extensors and plantar-flexors. Additionally, a subset of participants (N.=10 for each group) underwent a fatigue-inducing exercise-till-exhaustion protocol, and the strength of lower limb and respiratory muscles was evaluated immediately before and after the trial. Athletes had bigger and stronger musculotendinous structures and greater endurance to fatigue than CN (P<0.05). BP had bigger plantar-flexors and diaphragm, greater fascicles length, more explosive plantar-flexors and respiratory muscles and bigger tendons than CY (P<0.05). On the other hand, CY showed greater muscle pennation angle and greater endurance to fatigue for both, lower limb, and respiratory muscles (P<0.05). The present study emphasizes that chronic and specific exercise training leads to distinctive adaptations, not only in lower limb musculotendinous structures but also in other components such as respiratory muscles.

Submaximal eccentric resistance training increases serial sarcomere number and improves dynamic muscle performance in old rats.

The age-related loss of muscle mass is partly accounted for by the loss of sarcomeres in series, contributing to declines in muscle mechanical performance. Resistance training biased to eccentric contractions increases serial sarcomere number (SSN) in young muscle, however, maximal eccentric training in old rats previously did not alter SSN and worsened performance. A submaximal eccentric training stimulus may be more conducive to adaptation for aged muscle. The purpose of this study was to assess whether submaximal eccentric training can increase SSN and improve mechanical function in old rats. Twelve 32-month-old male F344/BN rats completed 4 weeks of submaximal (60% maximum) eccentric plantar-flexion training 3 days/week. Pre- and post-training, we assessed in-vivo maximum isometric torque at a stretched and neutral ankle angle, the passive torque-angle relationship, and the isotonic torque-velocity-power relationship. The soleus and medial gastrocnemius (MG) were harvested for SSN measurements via laser diffraction, with the untrained leg as a control. SSN increased 11% and 8% in the soleus and MG, respectively. Training also shifted optimal torque production towards longer muscle lengths, reduced passive torque 42%, and increased peak isotonic power 23%. Submaximal eccentric training was beneficial for aged muscle adaptations, increasing SSN, reducing muscle passive tension, and improving dynamic contractile performance.

“When hearing hoof beats from behind, expect horses, not zebras” – What flexibility research should adopt from scientific philosophy. A critical perspective on available evidence

The American College of Sports Medicine classifies flexibility as one out of 5 important health-related parameters that should be addressed in preventive and therapeutic training programs (Garber et al., 2011). Due to its importance in health and athletic performance development, there is an increasing number of studies to figure out flexibility training interventions as well as underlying mechanisms. While several exercise modalities are available, stretching and foam rolling (FR) are the most common training routines to improve range of motion (ROM). Interestingly, acute and chronic effects are mainly attributed to very similar mechanisms, more specifically, improved stretch tolerance and/or structural adaptations such as stiffness reductions in the muscle, the tendon, or the muscle-tendon complex (Takeuchi et al., 2023). Since stretching and FR seem to induce similar effect sizes in acute flexibility, authors suggested the replacement of static stretching to FR in movement preparation routines to avoid the stretch-induced force deficit, thus, impairments of subsequent strength related performance. Similarly, when discussing chronic flexibility routine effects, literature suggests task specificity. Therefore, increased ROM was attributed to specific stretch/foam rolling induced stiffness and passive peak torque changes. Unfortunately, statements developed from used research designs are incomprehensive. When referring to acute stretching of foam rolling effects that can be extracted from numerous systematic reviews, conclusions were drawn from comparisons to passive controls. This, however, does exclusively allow statements that stretching/FR was effective compared to doing nothing, however, does not exclude general warm-up effects, induced by muscle activity. Referring to William of Ockham (1287 – 1347), one popular philosopher from the United Kingdom, the most obvious explanatory approach would be the most likely one. In medicine diagnostics, this statement is metaphorically described as “when hearing hoof beats from behind, expect horses, not zebras”. Therefore, since both routines enhance temperature, the most likely explanation suggest acute ROM increases could rely on general warm-up effects instead of task-specific adaptations. Similarly, for chronic effects, literature suggests that ROM can be increased by several alternative interventions, e.g. full ROM resistance training, indicating shared mechanisms. Both interventions share underlying physiological mechanisms, such as inducing mechanical tension in high muscle lengths. Consequently, we extensively discussed available evidence in our published research. Key findings will be presented to challenge current paradigms (Warneke et al., 2024). References Garber, C. E., Blissmer, B., Deschenes, M. R., Franklin, B. A., Lamonte, M. J., Lee, I.-M., Nieman, D. C., &amp; Swain, D. P. (2011). Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults. Medicine &amp; Science in Sports &amp; Exercise, 43(7), 1334–1359. https://doi.org/10.1249/MSS.0b013e318213fefb Takeuchi, K., Nakamura, M., Fukaya, T., Konrad, A., &amp; Mizuno, T. (2023). Acute and long-term effects of static stretching on muscle-tendon unit stiffness: A systematic review and meta-analysis. Journal of Sports Science and Medicine, 22, 465–475. https://doi.org/10.52082/jssm.2023.465 Warneke, K., Behm, D. G., Alizadeh, S., Hillebrecht, M., Konrad, A., &amp; Wirth, K. (2024). Discussing conflicting explanatory approaches in flexibility training under consideration of physiology - A narrative review. Sports Medicine, 54, 1785-1799. https://doi.org/10.1007/s40279-024-02043-y

Age-related differences in the loss and recovery of serial sarcomere number following disuse atrophy in rats

BackgroundOlder adults exhibit a slower recovery of muscle mass following disuse atrophy than young adults. At a smaller scale, muscle fibre cross-sectional area (i.e., sarcomeres in parallel) exhibits this same pattern. Less is known, however, about age-related differences in the recovery of muscle fibre length, driven by increases in serial sarcomere number (SSN), following disuse. The purpose of this study was to investigate age-related differences in SSN adaptations and muscle mechanical function during and following muscle immobilization. We hypothesized that older adult rats would experience a similar magnitude of SSN loss during immobilization, however, take longer to recover SSN than young following cast removal, which would limit the recovery of muscle mechanical function.MethodsWe casted the plantar flexors of young (8 months) and old (32 months) male rats in a shortened position for 2 weeks, and assessed recovery during 4 weeks of voluntary ambulation. Following sacrifice, legs were fixed in formalin for measurement of soleus SSN and physiological cross-sectional area (PCSA) with the un-casted soleus acting as a control. Ultrasonographic measurements of pennation angle (PA) and muscle thickness (MT) were conducted weekly. In-vivo active and passive torque-angle relationships were constructed pre-cast, post-cast, and following 4 weeks of recovery.ResultsFrom pre- to post-cast, young and older adult rats experienced similar decreases in SSN (–20%, P < 0.001), muscle wet weight (–25%, P < 0.001), MT (–30%), PA (–15%, P < 0.001), and maximum isometric torque (–40%, P < 0.001), but there was a greater increase in passive torque in older (+ 180%, P < 0.001) compared to young adult rats (+ 68%, P = 0.006). Following cast removal, young exhibited quicker recovery of SSN and MT than old, but SSN recovered sooner than PA and MT in both young and old. PCSA nearly recovered and active torque fully recovered in young adult rats, whereas in older adult rats these remained unrecovered at ∼ 75%.ConclusionsThis study showed that older adult rats retain a better ability to recover longitudinal compared to parallel muscle morphology following cast removal, making SSN a highly adaptable target for improving muscle function in elderly populations early on during rehabilitation.

Clinical and biomechanical characteristics of responders and non-responders to insoles in individuals with excessive foot pronation during walking

This study aimed to identify the clinical and biomechanical factors of subjects with excessive foot pronation who are not responsive (i.e., “non-responders”) to medially wedged insoles to increase knee adduction external moment. Ankle dorsiflexion range of motion, forefoot-shank alignment, passive hip stiffness, and midfoot passive resistance of 25 adults with excessive bilateral pronation were measured. Also, lower-limb angles and external moments were computed during walking with the participants using control (flat surface) and intervention insoles (arch support and 6° medial heel wedge). A comparison between “responders” (n = 34) and “non-responders” (n = 11) was conducted using discrete and continuous analyses. Compared with the responders, the non-responders had smaller forefoot varus (p = 0.014), larger midfoot passive internal torque peak (p = 0.005), and stiffness measured by the torsimeter (p = 0.022). During walking, non-responders had lower angle peaks for forefoot eversion (p = 0.001), external forefoot rotation (p = 0.037), rearfoot eversion (p = 0.022), knee adduction (p = 0.045), and external hip rotation (p = 0.022) and higher hip internal rotation angle peak (p = 0.026). Participants with small forefoot varus alignment, large midfoot passive internal torque, stiffness, small knee valgus, hip rotated internally, and foot-toed-in during walking did not modify the external knee adduction moment (“non-responders”). Clinicians are advised to interpret these findings with caution when considering the prescription of insoles. Further investigation is warranted to fully comprehend the response to insole interventions among individuals with specific pathologies, such as patellofemoral pain and knee osteoarthritis (OA).

Effect of 6-Week Instrument-Assisted Soft Tissue Mobilization on Joint Flexibility and Musculotendinous Properties.

Instrument-assisted soft tissue mobilization (IASTM) stimulates soft subcutaneous tissues by applying pressure to the skin with a specialized bar or spurtle-like instrument. No studies have verified whether several weeks of continuous IASTM alone can alter joint flexibility and musculotendinous properties in healthy participants. We examined the effect of a 6-week IASTM program on joint flexibility and the musculotendinous properties of the lower limbs. Fourteen healthy men (aged 19-35 years) who participated in a 6-week IASTM program (3 days weekly) for the soft tissue of the posterior aspect of one lower leg were included. The other leg served as the control. Before and after the intervention, we measured the maximal ankle joint dorsiflexion angle (dorsiflexion range of motion: DFROM) and maximal passive torque (MPT), a measure of stretch tolerance. We measured muscle and tendon stiffness using shear wave elastography on the gastrocnemius and Achilles tendon. IASTM significantly increased the DFROM and MPT (p < 0.05 for both). However, no significant changes were observed in muscle and tendon stiffness. None of the parameters changed significantly in the control group. The 6-week IASTM program increased stretch tolerance and joint flexibility but did not change muscle and tendon stiffness.

Age-related blunting of serial sarcomerogenesis and mechanical adaptations following 4 weeks of maximal eccentric resistance training

During natural aging, muscles atrophy, which is partly accounted for by a loss of sarcomeres in series. Serial sarcomere number (SSN) is associated with aspects of muscle mechanical function including the force-length and force-velocity-power relationships; hence, the age-related loss of SSN contributes to declining performance. Training emphasizing muscle lengthening (eccentric) contractions increases SSN in young healthy rodents. However, the ability for eccentric training to increase SSN and improve mechanical function in old age is unknown. Older individuals often exhibit a blunted ability for training-induced hypertrophic adaptations. Therefore, the purpose of this study was to investigate the sarcomerogenic response to eccentric training in old rats. We hypothesized that old rats would experience a smaller magnitude of serial sarcomerogenesis than young rats, which would correspond to smaller beneficial adaptations in mechanical function as compared with young. Ten young (9 months) and 11 old (33 months) Fisher344/BN F1 rats completed 4 weeks of unilateral isokinetic eccentric plantar flexion training 3 days/week. Pre- and post-training, the plantar flexors were assessed for maximum tetanic torque (ankle angles of 70° and 90°), the torque-frequency relationship (stimulation frequencies of 1-100 Hz), the passive torque-angle relationship (ankle angles of 110-70°), and the torque-angular velocity-power relationship (isotonic loads of 10%-80% maximum). Following post-training testing, rats were sacrificed, and the soleus, lateral gastrocnemius (LG), and medial gastrocnemius (MG) were harvested for SSN assessment by measuring sarcomere lengths with laser diffraction, with the untrained leg used as a control. In the untrained leg/pre-training, old rats had lower SSN in the soleus (−9%), LG (−7%), and MG (−14%), lower maximum torque (−27 to −42%), power (−63%), and shortening velocity (−35%), and greater passive torque (+62 to +191%) than young. Young rats showed 6% increased SSN from the untrained to the trained soleus and MG. In contrast, old rats had no change in soleus SSN, only a 2% increase in MG SSN, and 4% SSN loss in the LG. Young rats saw modest improvements in isometric mechanical function, including a 13% increase in maximum torque at 90° and 4-11% increases in 10-60 Hz torque. Old rats, however, had reductions in maximum torque (−35%), shortening velocity (−46%), and power (−63%), and increased passive torque (+24 to +51%). Altogether, eccentric training induced serial sarcomerogenesis and improved mechanical function in young rats, while old rats exhibited dysfunctional remodelling that led to impaired muscle mechanical performance. Supported by NSERC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of foam rolling on hamstrings stiffness in damaged and non-damaged muscle states.

Introduction: The aim of this study was to examine the effects of foam rolling (FR) on hamstring muscles stiffness in both non-damaged and exercise-induced muscle damage (EIMD) states, using shear wave ultrasound elastography to measure changes in shear modulus. Methods: Fourteen healthy adults (25.5 ± 4.7 years) participated in a within-participant repeated measures design, with a 2-minute FR intervention applied on one leg and contralateral leg serving as a control. The damaging protocol encompassed maximal eccentric knee extensions performed on an isokinetic dynamometer and the Nordic hamstring exercise, consisting of 3 sets of 10 and 6 repetitions, respectively. Measurement were taken at baseline and then 1h, 24h and 48h after the damaging protocol. Results: The results indicated no significant time × leg interaction for shear modulus in biceps femoris, semimembranosus, and semitendinosus muscles in both non-damaged and damaged states. Notably, there was a significant increase in biceps femoris (p = 0.001; η2 = 0.36) and semitendinosus (p < 0.001; η2 = 0.44) shear modulus after EIMD, but no significant differences were found between the FR and control leg, which was also the case for muscle soreness, range of motion, and passive resistive torque (p = 0.239-0.999 for interactions). Discussion: The absence of significant changes post-FR intervention suggests a limited role of short-duration FR in altering muscle stiffness during recovery from EIMD. These findings contribute to the understanding of FR's role in muscle recovery. Although this was not directly investigated, our results suggest a predominance of central mechanisms rather than direct mechanical modifications in muscle properties. This research highlights the necessity for additional investigations to explore how FR interventions influence muscles in different states and to elucidate the mechanisms underlying these influences.

Combined Effects of Static and Dynamic Stretching on the Muscle-Tendon Unit Stiffness and Strength of the Hamstrings.

Takeuchi, K, Nakamura, M, Matsuo, S, Samukawa, M, Yamaguchi, T, and Mizuno, T. Combined effects of static and dynamic stretching on the muscle-tendon unit stiffness and strength of the hamstrings. J Strength Cond Res 38(4): 681-686, 2024-Combined static and dynamic stretching for 30 seconds is frequently used as a part of a warm-up program. However, a stretching method that can both decrease muscle-tendon unit (MTU) stiffness and increase muscle strength has not been developed. The purpose of this study was to examine the combined effects of 30 seconds of static stretching at different intensities (normal-intensity static stretching [NS] and high-intensity static [HS]) and dynamic stretching at different speeds (low-speed dynamic [LD] and high-speed dynamic stretching [HD]) on the MTU stiffness and muscle strength of the hamstrings. Thirteen healthy subjects (9 men and 4 women, 20.9 ± 0.8 years, 169.3 ± 7.2 cm, 61.1 ± 8.2 kg) performed 4 types of interventions (HS-HD, HS-LD, NS-HD, and NS-LD). Range of motion (ROM), passive torque, MTU stiffness, and muscle strength were measured before and immediately after interventions by using an isokinetic dynamometer machine. In all interventions, the ROM and passive torque significantly increased (p < 0.01). Muscle-tendon unit stiffness significantly decreased in HS-HD and HS-LD (both p < 0.01), but there was no significant change in NS-HD (p = 0.30) or NS-LD (p = 0.42). Muscle strength significantly increased after HS-HD (p = 0.02) and NS-LD (p = 0.03), but there was no significant change in HS-LD (p = 0.23) or NS-LD (p = 0.26). The results indicated that using a combination of 30 seconds of high-intensity static stretching and high-speed dynamic stretching can be beneficial for the MTU stiffness and muscle strength of the hamstrings.

The Effects of 5 Minutes of Static Stretching on Joint Flexibility and Muscle Strength Are Comparable Between Ballet Dancers and Non-Dancers.

Introduction: Ballet dancers have a special morphology, such as a large muscle thickness that affects passive torque. Ballet dancers also possess specialized mechanical, and neural properties of muscles and tendons. These characteristics may produce different static stretching effects than non-dancers. Therefore, this study aimed to determine the differences in the effects of static stretching on joint range of motion, passive torque, and muscle strength between ballet dancers and non-dancers. Methods: This study included 13 ballet dancers and 13 college students. The muscle and tendon thicknesses were assessed using ultrasonography. In the right lower extremity, torque-angle data and muscle-tendon junction displacement measurements were obtained during isokinetic passive dorsiflexion before and after a 5-minute static stretch against the right plantar flexors. The relative stretching intensity was calculated by dividing the stretching angle by the maximal dorsiflexion angle pre-stretch. Additionally, the isometric maximal voluntary plantar flexion torque on the left ankle was measured before and after 5 minutes of static stretching against the left plantar flexors. Results: Ballet dancers had significantly greater muscle thickness than non-dancers (22.4 ± 2.2 vs 18.1 ± 1.7 mm), whereas no significant difference was observed in the Achilles tendon thickness. No significant difference was observed in the stretching angle; however, the relative stretching intensity was higher in the control group (65.9 ± 19.8 vs 127.5 ± 63.8%). Static stretching increased the maximal dorsiflexion angle (dancer: 30.4° ± 9.6° to 33.9° ± 9.5°, non-dancer: 18.4° ± 8.6° to 20.5° ± 9.5°) and maximal passive torque in both groups, whereas the maximal isometric plantar flexion torque and submaximal passive torque decreased. However, no significant differences were observed in the changes between the groups. Conclusion: These results indicate that despite having a lower relative stretching intensity, ballet dancers experienced similar changes as non-dancers after 5 minutes of static stretching.

Age-related blunting of serial sarcomerogenesis and mechanical adaptations following 4 wk of maximal eccentric resistance training.

During aging, muscles undergo atrophy, which is partly accounted for by a loss of sarcomeres in series. Serial sarcomere number (SSN) is associated with aspects of muscle mechanical function including the force-length and force-velocity-power relationships; hence, the age-related loss of SSN contributes to declining performance. Training emphasizing eccentric contractions increases SSN in young healthy rodents; however, the ability for eccentric training to increase SSN in old age is unknown. Ten young (8 mo) and 11 old (32 mo) male Fisher344/BN rats completed 4 wk of unilateral eccentric plantar flexion training. Pre- and posttraining, the plantar flexors were assessed for the torque-frequency, passive torque-angle, and torque-velocity-power relationships. The soleus, lateral gastrocnemius (LG), and medial gastrocnemius (MG) were harvested for SSN assessment via laser diffraction, with the untrained leg used as a control. In the untrained leg/pretraining, old rats had lower SSN in the soleus, LG, and MG, lower maximum torque, power, and shortening velocity, and greater passive torque than young. Young showed increased soleus and MG SSN following training. In contrast, old had no change in soleus SSN and experienced SSN loss in the LG. Pre- to posttraining, young experienced an increase in maximum isometric torque, whereas old had reductions in maximum torque, shortening velocity, and power, and increased passive torque. Our results show that although young muscle has the ability to add sarcomeres in response to maximal eccentric training, this stimulus could be not only ineffective, but also detrimental to aged muscle leading to dysfunctional remodeling.NEW & NOTEWORTHY The loss of sarcomeres in series with age contributes to declining muscle performance. The present study investigated whether eccentric training could improve performance via serial sarcomere addition in old muscle, like in young muscle. Four weeks of maximal eccentric training induced serial sarcomere addition in the young rat plantar flexors and improved in vivo performance, however, led to dysfunctional remodeling accompanied by further impaired performance in old rats.

The Acute Effect of Percussive Massage Intervention with and without Heat Application on Plantar Flexor Muscles' Passive and Active Properties.

Recently, percussive massage (PM) intervention using a handheld percussive massage device, namely a massage gun, has been used as an easy way to perform vibration functions. Additionally, a product has been developed that allows PM intervention and heat application to be performed simultaneously. Thus, this study aimed to compare the acute effects of PM intervention with and without heat application on dorsiflexion (DF) range of motion (ROM), passive stiffness, and muscle strength in the gastrocnemius muscle. Fifteen healthy young men (20.9 ± 0.2 years) participated in this study. We measured the DF ROM, passive torque at DF ROM (an indicator of stretch tolerance), passive stiffness, and maximum voluntary isometric contraction (MVIC) torque of the plantar flexor muscles before and immediately after 120 seconds PM intervention with and without heat application. The results showed that PM intervention with and without heat application significantly increased DF ROM and passive torque at DF ROM and decreased passive stiffness, not MVIC torque. These results suggest that PM intervention increased ROM and decreased passive stiffness regardless of the presence or absence of the heat application.

Regional and widespread pain sensitivity decreases following stretching in both men and women – Indications of stretch-induced hypoalgesia

IntroductionThis study aimed to investigate the effect of sex on regional and widespread pain sensitivity following acute bouts of stretching and to investigate the acute effect of stretching on regional and widespread pain sensitivity following stretching. Methods73 healthy adults (36 females; mean age 25.6 ± 6.7 years) with an age range from 19 to 62 years were recruited for this experimental study. Regional and distant pain pressure pain thresholds, passive knee extension range of motion and passive resistive torque were measured before and 30 s after four bouts of 30-s static muscle stretching of the knee flexors with 20-s rest between bouts. ResultsNo significant sex differences were found for pressure pain thresholds (p > 0.132), range of motion (p = 0.446) or passive resistive torque (p = 0.559) between pre-stretch and post-stretch measures. There were significant increases in pressure pain thresholds (p = 0.010), range of motion (p = 0.001) and passive resistive torque (p = 0.007) between pre-stretch and post-stretch measures. ConclusionMuscle stretching significantly decreased regional and widespread pain sensitivity, indicating that central pain-modulating mechanisms are engaged during muscle stretching, resulting in stretch-induced hypoalgesia. Moreover, the results showed that the effect of stretching on regional and widespread pain sensitivity is not sex-specific.

Reductions in rearfoot eversion posture due to proximal muscle strengthening are dependent on foot-ankle varus alignment

BackgroundStrengthening the hip and trunk muscles may decrease foot pronation in upright standing due to expected increases in hip passive torque and lower-limb external rotation. However, considering the increased pronation caused by a more varus foot-ankle alignment, subjects with more varus may experience smaller or no postural changes after strengthening. ObjectiveTo investigate the effects of hip and trunk muscle strengthening on lower-limb posture during upright standing and hip passive torque of women with more and less varus alignment. MethodsThis nonrandomized controlled experimental study included 50 young, able-bodied women. The intervention group (n = 25) performed hip and trunk muscle strengthening exercises, and the control group (n = 25) maintained their usual activities. Each group was split into two subgroups: those with more and less varus alignment. Hip, shank, and rearfoot-ankle posture and hip passive external rotation torque were evaluated. Mixed analyses of variance and preplanned contrasts were used to assess prepost changes and between-group differences (α = 0.05). ResultsThe less-varus subgroup of the intervention group had a reduced rearfoot eversion posture (P = 0.02). No significant changes were observed in the less-varus subgroup of the control group (P = 0.31). There were no significant differences in posture between the control and intervention groups when varus was not considered (P ≥ 0.06). The intervention group had increased hip passive torque (P = 0.001) compared to the control group, independent of varus alignment. ConclusionDespite the increases in hip passive torque, the rearfoot eversion posture was reduced only in women with a less-varus alignment. Having more foot-ankle varus may prevent eversion reductions.

A Rod-Type Passive and Wireless Torque and Bending Moment Sensor Working in a Self-Decoupled Mode

A Rod-Type Passive and Wireless Torque and Bending Moment Sensor Working in a Self-Decoupled Mode

Grey wolf optimization algorithm-based robust neural learning control of passive torque simulators with predetermined performance

Grey wolf optimization algorithm-based robust neural learning control of passive torque simulators with predetermined performance

Acute effects of resistance training at different range of motions on plantar flexion mechanical properties and force

ABSTRACT The effects obtained from resistance training depend on the exercise range of motion (ROM) performed. We aimed to examine the acute effects of different exercise ROM resistance training on the plantar flexor muscles. Eighteen healthy untrained male adults participated in three conditions: calf raises in 1) partial condition [final (short muscle length) partial ROM], 2) full condition (full ROM), and 3) control condition. The ankle dorsiflexion (DF) ROM, passive torque at DF ROM, passive stiffness of muscle-tendon unit, and maximal voluntary isometric contraction (MVC-ISO) torque were measured before and immediately after the interventions. There were significant increases in DF ROM, passive torque at DF ROM, and a decrease in MVC-ISO, but no significant interaction in passive stiffness. Post hoc test, DF ROM demonstrated moderate magnitude increases in the full condition compared to the partial (p = 0.023, d = 0.74) and control (p = 0.003, d = 0.71) conditions. Passive torque at DF ROM also showed moderate magnitude increases in the full condition compared to the control condition (p = 0.016, d = 0.69). MVC-ISO had a moderate magnitude decrease in the full condition compared to the control condition (p = 0.018, d=−0.53). Resistance training in the full ROM acutely increases joint ROM to a greater extent than final partial ROM, most likely due to stretch tolerance.

Changes in passive hamstring stiffness after primary anterior cruciate ligament reconstruction: A prospective study with comparison of healthy controls

BackgroundThe mechanical properties of knee flexors muscles contribute to reducing anterior cruciate ligament loading. This case-control study evaluated the passive knee flexors stiffness after primary anterior cruciate ligament reconstruction with comparison of healthy controls. MethodsAfter anterior cruciate ligament reconstruction, 88 participants (24.5 [8.6] years, 56,8% males) had two isokinetic tests at 4 and 8 postoperative months with measurement of the passive resistive torque of knee flexors and extensors/flexors strength. In the control group, 44 participants (24.5 [4.3] years, 56,8% males) had one visit with the same procedures. Passive knee flexors stiffness was calculated as the slope of the passive torque-angle curve on the last 10° of knee extension (Nm/°). We investigated the impact of timing and type of surgery (autograft and combined meniscus repair) and persistent knee extension deficits on knee flexors stiffness. FindingsAt 4 and 8 postoperative months, passive knee flexors stiffness was lower on the operated limb than on the non-operated limb (P < 0.001) but both limbs had significant lower values than controls (P < 0.001). Stiffness was positively correlated with knee flexors strength (P < 0.010), and knee flexors stiffness at 4 months was lower in individuals who underwent surgery <6 months from injury (P = 0.040). Knee extension deficit or the type of surgery did not have a significant influence on knee flexors stiffness. InterpretationSimilarly to neuromuscular factors that are traditionally altered after anterior cruciate ligament reconstruction, evaluating passive knee flexors stiffness changes over time could provide supplementary insights into postoperative muscle recovery.

Acute and Chronic Effects of Static Stretching on Neuromuscular Properties: A Meta-Analytical Review

The aim of this review was to provide an overview of the recent findings on the acute and chronic effects of static stretching on joint behaviors and neuromuscular responses and to discuss the overall effects of acute and chronic static stretching on selected outcomes via meta-analyses, using a total of 50 recent studies. The results of our meta-analyses demonstrated that acute static stretching results in increased range of motion (ROM), decreased passive resistive torque (PRT), increased maximum tolerable PRT (PRTmax), decreased maximum voluntary isometric torque, decreased muscle–tendon unit stiffness, decreased muscle stiffness, decreased tendon stiffness, and decreased shear elastic modulus. Moreover, the chronic effects of static stretching included increased ROM, increased PRTmax, decreased muscle stiffness, and decreased shear elastic modulus (or shear wave speed). These results suggest that static stretching interventions have the potential to increase ROM and reduce the mechanical properties of muscle–tendon tissue, but they may not change corticospinal excitability and spinal reflex excitability or muscle architecture parameters.

Effects of eccentric contraction on force enhancement in rat fast-twitch muscle.

The aim of this study was to elucidate the effects of eccentric contraction (ECC) on force enhancement in rat fast-twitch skeletal muscle. Gastrocnemius (GAS) muscles were subjected to 200 ECCs in situ by electrical stimulation. Immediately before and after the stimulation, isometric torque produced by ankle flexion was measured at an ankle angle of 90°. After the second torque measurement, the superficial regions of the muscles were dissected and subjected to biochemical and skinned fiber analysis. ECC did not induce changes in the amount of degraded titin. After ECC, isometric torques in the GAS muscles were markedly reduced, especially at low stimulation frequency. ECC increased passive torque in whole muscle and passive force in skinned fibers. Passive force enhancement and the ratio of passive force to the maximal Ca2+ -activated force, but not residual force enhancement, were augmented in the skinned fibers subjected to ECC. An ECC-induced increase in titin-based stiffness may contribute to the increased PFE. These results suggest that skeletal muscle is endowed with a force potentiation system that can attenuate ECC-induced force reductions.