Muscle passive stiffness increases less after the second bout of eccentric exercise compared to the first bout

Assessment of the stiffness of the upper trapezius muscle in a group of asymptomatic people with cervical spine rotation asymmetry

This study investigated the relationship between the stiffness of the upper trapezius muscle and the range of rotational movement of the cervical spine. A total of 60 right-handed asymptomatic students participated in the study. Participants (N = 22) characterised by asymmetry in rotational movements were selected for the experimental group. A difference of ≥10° between right and left rotation of the cervical spine was considered asymmetrical. The control group (N = 38) included participants whose rotation difference was < 10°. Belonging to the experimental or control group did not significantly differentiate trapezius muscle stiffness. The rotation side differentiated the stiffness of the right and left trapezius muscles only in the group of people with rotational movement asymmetry. There were high correlation coefficients between right cervical rotation and the stiffness of the muscle on the right side, and between rotation to the left and the stiffness of the muscle on the left side. There is a relationship between the stiffness of the right and left upper trapezius muscles and the range of right and left rotational motion of the cervical spine. Stiffness of the upper trapezius correlates more strongly with rotation to the side on which the muscle lies than to the opposite side. Increased stiffness of the upper trapezius muscle on the side of limited cervical spine rotation is likely to be determined by the muscle fibre stretching mechanism.

Effects of two-week machine massage on muscle properties in adolescent wrestlers

Objective: This study aimed to investigate the effect of a two-week machine massage on the physical properties of the erector spinae and serum biochemical indexes of adolescent athletes after training. Methods: Sixteen male adolescent wrestlers were recruited (age: 15 ± 1 year; height: 166 ± 7 cm; weight: 56 ± 7 kg) and randomly assigned to machine massage (MA, 8) and control (CO, 8) groups. Participants in the MA group received machine massage for 20 min after each wrestling training from Monday to Saturday (except on Thursday) for two weeks, while the participants in the CO group recovered naturally. Over the course of two weeks, all the participants underwent similar wrestling training program under the guidance of a professional coach. Before and after the intervention, serum urea and creatine kinase (CK) levels were measured in a fasting state. A Myoton Pro digital muscle evaluation system was used to measure the physical properties of the erector spinae, including the oscillation frequency, logarithmic decrement of a muscle's natural oscillation, and dynamic stiffness. Results: After two weeks of machine massage treatment, the dynamic stiffness of the erector spinae in the MA group decreased by 12.90% and that in the CO group increased by 2.34%, indicating a significant difference between the two groups (p = 0.04, ƞ ² = 0.286). The decrease in the logarithmic decrement of a muscle's natural oscillation value in the MA was significantly greater than that in the CO (p = 0.003, ƞ ² = 0.286). Moreover, the serum CK values decreased by 33.84% in the MA group and by 1.49% in the CO group, despite a trend of change between the groups (p = 0.062, ƞ2 = 0.084). No significant difference was found in the improvement in serum urea levels between the two groups after two weeks of treatment. Conclusion: Results of the present study indicated that a two-week machine massage had a positive effect on the improvement of the physical properties of the erector spinae of wrestlers during training.

Muscle Architecture, Morphology, and Mechanical and Functional Properties of Biceps Femoris Long Head in Professional Soccer Players with a Prior Healed Injured Hamstring

OBJECTIVE

The aim of the present study was to compare the fascicle length, pennation angle, muscle thickness and stiffness of the biceps femoris long head, and eccentric hamstring strength between injured dominant limbs, injured non-dominant limbs, uninjured dominant limbs and uninjured non-dominant legs in previously injured players, and between dominant and non-dominant legs in uninjured elite soccer players.

MATERIALS AND METHODS

Twenty elite soccer players participated in this study. Ultrasound imaging and MyotonPRO were used to determine the morphological and mechanical properties of the biceps femoris long head. Isokinetic and Nordic hamstring exercises were used to assess eccentric hamstring strength.

RESULTS

Previously injured players showed substantially lower fascicle length and muscle thickness, and significantly higher biceps femoris long head stiffness than uninjured players, without differences between limbs.

CONCLUSION

The morphological and mechanical properties of elite soccer players with hamstring injury history were different from those in uninjured players. The lack of differences between limbs showed that these values are characteristics of individual players that must be considered in the design of programs to prevent BFlh injury.

Using Shear-Wave Elastography to Assess Exercise-Induced Muscle Damage: A Review

Shear-wave elastography is a method that is increasingly used to assess muscle stiffness in clinical practice and human health research. Recently, shear-wave elastography has been suggested and used to assess exercise-induced muscle damage. This review aimed to summarize the current knowledge of the utility of shear-wave elastography for assessment of muscle damage. In general, the literature supports the shear-wave elastography as a promising method for assessment of muscle damage. Increases in shear modulus are reported immediately and up to several days after eccentric exercise, while studies using shear-wave elastography during and after endurance events are showing mixed results. Moreover, it seems that shear modulus increases are related to the decline in voluntary strength loss. We recommend that shear modulus is measured at multiple muscles within a muscle group and preferably at longer muscle lengths. While further studies are needed to confirm this, the disruption of calcium homeostasis seems to be the primary candidate for the underlying mechanism explaining the increases in shear modulus observed after eccentric exercise. It remains to be investigated how well the changes in shear modulus correlate with directly assessed amount of muscle damage (biopsy).

Effects on Neuromuscular Function After Ischemic Compression in Latent Trigger Points in the Gastrocnemius Muscles: A Randomized Within-Participant Clinical Trial

OBJECTIVE

The purpose of this study was to evaluate changes in neuromuscular function, pain perception, and basic physical properties in latent myofascial trigger points (TrPs) after a single treatment session of ischemic compression in the gastrocnemius muscle.

METHODS

A randomized within-participant clinical trial with a blinded assessor was conducted. Twenty-nine asymptomatic volunteers with latent gastrocnemius-muscle TrPs were bilaterally explored. Each extremity was randomly assigned to the control group (no treatment) or the experimental group (90 seconds of ischemic compression over each TrP). Neuromuscular function of the gastrocnemius muscle was assessed using a MyotonPro. Muscle flexibility was analyzed using the lunge test and the passive ankle range of motion. The strength was determined with a handheld dynamometer (MicroFET2). Pain perception was analyzed with a 0-to-10 numerical pain rating scale and determination of pressure pain thresholds over each latent TrP.

RESULTS

The results revealed a reduction of 15.8% in pain perception and an increment of pressure tolerance of 9.9% without pain in the treatment group. Changes in muscle flexibility (active and passive) and most parameters for neuromuscular response (rigidity, elasticity, and relaxation) were also observed, but they were not significantly different between groups. The clinical effect sizes were moderate for pain perception (d = 0.69), pressure pain threshold (d = 0.78), muscle tone (d = 0.51), and elasticity (d = 0.54) in favor of the treated extremity. Small clinical effect sizes were observed for muscle physical outcomes.

CONCLUSION

The present study shows that the use of a single session of ischemic compression for latent gastrocnemius-muscle TrPs improved some sensory outcomes. The effects on ankle range of motion and neuromuscular responses were inconclusive.

Protocol and reference values for minimal detectable change of MyotonPRO and ultrasound imaging measurements of muscle and subcutaneous tissue

The assessment of muscle health is of paramount importance, as the loss of muscle mass and strength can affect performance. Two non-invasive tools that have been found to be useful in this are the MyotonPRO and rehabilitative ultrasound imaging, both have shown to be reliable in previous studies many of which conducted by the research team. This study aims to determine the reliability of previously unassessed local body structures and to determine their minimal detectable changes (MDC) to support both researchers and clinicians. Twenty healthy participants were recruited to determine the reliability of seven skin positions out of a previously established protocol. Reliability was determined between three independent raters, and day to day reliability was assessed with one rater a week apart. Intraclass Correlation Coefficients (ICC) between raters and between days for tissue stiffness, tone and elasticity range from moderate to excellent (ICC 0.52–0.97), with most good or excellent. ICCs for subcutaneous thickness between days was good or excellent (ICC 0.86–0.91) and moderate to excellent between raters (ICC 0.72–0.96), in muscles it was moderate to excellent between raters and days (ICC 0.71–0.95). The protocol in this study is repeatable with overall good reliability, it also provides established MDC values for several measurement points.

The effects of eccentric exercise on passive hamstring muscle stiffness: Comparison of shear-wave elastography and passive knee torque outcomes

The aim of our study was to assess eccentric-exercise-induced changes in passive knee joint torque, passive knee joint stiffness and shear modulus at of the hamstring muscles. We hypothesized that eccentric exercise would elicit an increase in all outcomes. Fourteen healthy volunteers (age = 25.5±4.7 years) performed eccentric exercise protocol. Before and after 0h, 1h, 24h and 48h, we measured the shear modulus of hamstring muscles using shear-wave elastography and passive knee joint stiffness on isokinetic dynamometer. After eccentric exercise, the shear modulus of biceps femoris increased after 0h (22.4 ± 34.1 %; p = 0.021) and for semitendinosus after 0h (14.5 ± 4.9 %), 1h (16.2 ± 6.5 %) and 24h (16.6 ± 8.3 %) (p = 0.005-0.015). There were no changes for semimembranosus and no changes in passive knee joint moment measures. There were also no correlations between the two methods. Eccentric exercise increased shear modulus of hamstring muscles, while passive joint torque was not affected. This suggests that shear-wave elastography could be more sensitive than torque measures to intra-muscular changes induced by eccentric exercise.

Effects of Core Stabilization Exercise Programs on Changes in Erector Spinae Contractile Properties and Isokinetic Muscle Function of Adult Females with a Sedentary Lifestyle

This study aimed to investigate the effect of core stabilization exercises on the contractile properties and isokinetic muscle function of adult females with a sedentary lifestyle. We enrolled 105 adult females. Tensiomyography was performed on the erector spinae, and the isokinetic muscular functional test was performed on the trunk at an angular velocity of 60°/s and 90°/s. All participants performed the exercise for 60 min per day, 3 times a week, for 7 weeks. A Wilcoxon signed-rank test was performed at a significance level of 0.05. Tensiomyography (TMG) of the erector spinae revealed no significant post-exercise change in the contraction time; however, there was a significant post-exercise increase in the maximum radial displacement and mean velocity until 90% of the TMG was displaced. Additionally, the isokinetic muscular functional test of the trunk revealed a significant post-exercise increase in almost all variables. Our findings demonstrated that the core stabilization exercise reduced stiffness in the erector spinae, increased the velocity of erector spinae contraction, and effectively improved the isokinetic muscular function of the trunk.

Influence of Spinal Movements Associated with Physical Evaluation on Muscle Mechanical Properties of the Lumbar Paraspinal in Subjects with Acute Low Back Pain

This research aimed to identify changes in muscle mechanical properties (MMPs) when a standardized sequence of movements is performed and to determine the influence of acute low back pain (LBP) and age on the MMPs. Socio-demographic, clinical variables and MMPs were collected in 33 patients with LBP and 33 healthy controls. A 2 × 2 × 2 (group × age × time) analysis of variance (ANOVA) mixed model was used to determine the effect of the study factors on the different MMPs. There were no significant triple interactions. After the movements, tone and stiffness increased 0.37 Hz and 22.75 N/m, respectively, in subjects <35 years, independent of their clinical status. Relaxation showed differences by age in healthy subjects and creep in LBP subjects. Furthermore, elasticity was higher in <35 years (p < 0.001) without the influence of any other factor. In conclusion, sequenced movements can modify tone and stiffness as a function of age, while age-associated changes in viscoelastic characteristics depends on pain but not on movements. The MMPs should be assessed, not only at the beginning of the physical examination at rest, but also along the patient’s follow-up, depending on their pain and age, in a clinical setting.

Effects of Dry Needling of Latent Trigger Points on Viscoelastic and Muscular Contractile Properties: Preliminary Results of a Randomized Within-Participant Clinical Trial

This study aimed to evaluate changes in neuromuscular function and pain perception in latent trigger points (TrPs) in the gastrocnemius muscle after a single session of dry needling. A randomized within-participant clinical trial was conducted. Fifty volunteers with latent TrPs in the gastrocnemius muscles were explored. Each extremity was randomly assigned to a control or experimental (dry needling) group. Viscoelastic parameters and contractile properties were analyzed by tensiomyography. Ankle dorsiflexion range of motion was assessed with the lunge test. Pressure pain thresholds (PPT) and pain perceived were also analyzed. The results observed that three viscoelastic proprieties (myotonometry) showed significant differences in favor of the experimental extremity in the lateral gastrocnemius: stiffness (p = 0.02), relaxation (p = 0.045), and creep (p = 0.03), but not in the medial gastrocnemius. No changes in tensiomyography outcomes were found. The control extremity showed a higher increase in PPTs (i.e., decrease in pressure pain sensitivity) than the experimental extremity (p = 0.03). No significant effects for range of motion or strength were observed. In general, gender did not influence the effects of dry needling over latent TrPs in the gastrocnemius muscle. In conclusion, a single session of dry needling was able to change some parameters of neuromuscular function, such as muscle tone, relaxation, pressure pain sensitivity, and creep in the lateral (but not medial) gastrocnemius but did not improve strength or range of motion.

Response of Knee Extensor Muscle-Tendon Unit Stiffness to Unaccustomed and Repeated High-Volume Eccentric Exercise

The purposes of this study were to investigate the muscle-tendon unit stiffness response and to compare the stiffness with those of other indirect markers induced by two bouts of unaccustomed eccentric exercise. Eleven untrained men performed two bouts of 200 maximal eccentric contractions of the right quadriceps 4 weeks apart. Changes in stiffness, pain evoked by stretching and pressure, plasma creatine kinase (CK) activity, and muscle thickness were followed for 7 days after each bout. Stiffness and pain peaked immediately and 1 day after the first exercise bout, whereas CK and thickness were highest 4 and 7 days after the first exercise bout, respectively (p < 0.05 for all). Muscular pain, thickness, and stiffness responses were lower by 53.3%, 99%, and 11.6%, respectively, after the repeated bout compared to after the first bout (p < 0.05 for all), while CK activity response did not differ significantly between bouts. High responders for an increase in muscle-tendon unit stiffness showed a repeated-bout effect for stiffness, pain, and CK activity (by 29%, 65%, and 98%, p < 0.05 for all), but the repeated-bout effect was not that clear in low responders. These findings suggest that a repeated eccentric exercise bout effect on stiffness in quadriceps is mostly not associated with muscle pain and CK activity, but there are large individual differences.

Comparison of the Immediate Effect of Petrissage Massage and Manual Lymph Drainage Following Exercise on Biomechanical and Viscoelastic Properties of the Rectus Femoris Muscle in Women

CONTEXT

Fast and adequate recovery after exercise and activity is important for increasing performance and preventing injuries. Inadequate recovery usually causes changes in the biomechanical and viscoelastic properties of the muscle.

OBJECTIVE

To compare the immediate effect of petrissage massage (PM) and manual lymph drainage (MLD) following submaximal exercise on the biomechanical and viscoelastic properties of the rectus femoris muscle in healthy women.

DESIGN

Cross-sectional, repeated-measures.

SETTING

Marmara University.

PARTICIPANTS

18 healthy female students.

INTERVENTION(S)

Following the submaximal quadriceps strengthening exercise performed in 3 sets of 8 repetitions with intensity of 75% of 1 maximum repetition, participants' right leg received a 5-minute PM (PM group) and the contralateral leg received a 5-minute MLD application (MLD group).

MAIN OUTCOME MEASURES

Skin temperature was measured using P45 thermographic thermal camera (Flir System; ThermaCAM, Danderyd, Sweden), and muscle tone, biomechanical, and viscoelastic features were measured with a myometer (Myoton AS, Tallinn, Estonia) at baseline, immediately postexercise, post-PM/MLD application, and 10 minutes postexercise.

RESULTS

In the PM group, the tonus (P = .002) and stiffness (P < .001) values measured after the massage and at the end of the 10-minute resting period were found to be statistically different than those measured right after the exercise (P < .05). Relaxation time and creep values at all measurement times were significantly different (P < .05). In the MLD group, it was observed the tonus (P < .001), stiffness (P = .025), and relaxation time (P < .01) values decreased significantly after the MLD compared with the values measured after the exercise; however, the creep value was found to be significantly different in all measurements (P < .05).

CONCLUSION

PM and MLD reduce passive tissue stiffness and improve the extent of muscle extensibility over time against the muscle tensile strength. PM and MLD are therapeutic methods that can be used to support tissue recovery after exercise and prevent injuries.

Normative data and correlation between dynamic knee valgus and neuromuscular response among healthy active males: a cross-sectional study

The dynamic knee valgus (DKV) during different sport maneuvers has been widely described as risk factor to develop an anterior cruciate ligament injury. Hip and knee muscles seem to have a crucial role to prevent the dynamic knee valgus. This study aimed to give normative and correlational data about DKV and hip and knee neuromuscular response (NMR) among healthy active males. The hypothesis is that DKV could be correlated with hip NMR. A cross-sectional correlational study. Research Anatomy Laboratory. The study was carried out among 50 active, non-injured males. Dynamic Knee-Valgus angle and lower limb posterior chain muscles Neuromuscular Response. DKV was measured using Kinovea software during a Single-Legged Drop Jump test and NMR was measured using tensiomyography and myotonometry for gluteus maximum, biceps femoris, semitendinosus, lateral and medial gastrocnemius. Right and left limbs were both performed and analyzed independently. No significant correlation was observed between DKV and hip and knee muscles NMR. This study shows normative and correlational data about dynamic knee valgus, tensiomyography and myotonometry for healthy and active males. The DKV control seems to be non-correlated with isolated hip and knee muscles NMR so this suggests it is more about Central Nervous System activity than about isolated muscles NMR.

Cold-Water Immersion Has No Effect on Muscle Stiffness After Exercise-Induced Muscle Damage

OBJECTIVE

To analyze the effect of cryotherapy on muscle stiffness after exercise-induced muscle damage.

DESIGN

A leg-to-leg comparison model.

SETTING

University research laboratory.

PARTICIPANTS

Thirty (30) untrained men (21.1 ± 1.6 years, 177.6 ± 6.4 cm, 75.9 ± 10.0 kg, and 15.9 ± 2.9% fat mass) with no history of lower-limb injury and no experience in resistance training.

INTERVENTION

All participants underwent a plyometric exercise program to induce muscle damage; however, randomly, one leg was assigned to a treatment condition and subjected twice to cold-water immersion of the lower limb at 10°C (±1°C) for 10 minutes, while the other leg was assigned to control.

MAIN OUTCOMES MEASURES

Longitudinal stiffness and passive transverse stiffness were evaluated on the soleus and gastrocnemius muscles at 4 moments: pre-exercise, immediately after exercise, 24 hours, and 72 hours after the damage protocol. Furthermore, pressure pain threshold (PPT) and maximal voluntary isometric contraction (MVIC) were also assessed in the same periods.

RESULTS

No significant differences between control and cryotherapy were observed in regard to MVIC (P = 0.529), passive longitudinal stiffness (P = 0.315), and passive transverse stiffness (P = 0.218). Only a significant decrease was observed in PPT on the soleus muscle in the cryotherapy compared with the control leg immediately after exercise (P = 0.040).

CONCLUSIONS

The results show that cryotherapy had no influence on muscle stiffness. However, cryotherapy had a positive effect on PPT immediately after exercise.

Eccentric Training Changes the Pressure Pain and Stiffness Maps of the Upper Trapezius in Females with Chronic Neck-Shoulder Pain: A Preliminary Study

OBJECTIVE

Between 50% and 67% of adults suffer from neck-shoulder pain, which may be associated with increased stiffness of neck muscles. We assessed pressure pain sensitivity and muscle stiffness maps of the upper trapezius in female computer users with and without chronic neck-shoulder pain and investigated the effects of eccentric training on females with neck-shoulder pain.

DESIGN

Cross-sectional (part 1) and open-label (part 2) study.

SETTING

University.

SUBJECTS

Twenty females with neck-shoulder pain were compared with 20 controls (part 1). In part 2, neck-shoulder pain participants followed a five-week unilateral upper trapezius eccentric training program.

METHODS

Topographical maps of pressure pain thresholds (pressure algometer) and muscle stiffness (myotonometer), using a 15-point grid covering myotendinous and muscle belly sites, and shoulder elevation force and range of elevation (dynamometer) were assessed at baseline and after training.

RESULTS

There were no differences in pressure pain thresholds between sites (P = 0.243) or groups (P = 0.068), and there were significant differences in stiffness between myotendinous and muscle belly sites (P < 0.001) but not groups (P = 0.273). After training, pressure pain thresholds increased, stiffness decreased (P < 0.005), and shoulder elevation force and range of elevation improved (P < 0.001).

CONCLUSIONS

The lack of differences in upper trapezius pressure pain sensitivity and stiffness between females with or without neck-shoulder pain confirms no clear etiology among computer users reporting neck-shoulder pain. A five-week eccentric training protocol showed positive effects on pressure pain sensitivity, stiffness, shoulder force, and range of motion.

Effect of Fatigue Protocols on Upper Extremity Neuromuscular Function and Implications for Ulnar Collateral Ligament Injury Prevention

Background

As the incidence of overuse injuries to the medial elbow in overhead athletes continues to rise, recent evidence suggests a link between these injuries and alterations in biomechanics produced by athlete fatigue. Previous studies have evaluated the effect of fatigue on elbow injuries using a wide array of fatigue protocols/athletic tasks, and, as a consequence, the results have been heterogeneous.

Purpose

To determine whether there is a uniform alteration in neuromuscular function or biomechanics as the overhead athlete fatigues. Furthermore, this study sought to determine whether player fatigue should be accounted for in ulnar collateral ligament (UCL) injury prevention programs.

Study Design

Systematic review.

Methods

A systematic review of the literature using PubMed and MEDLINE databases was performed. Keywords included fatigue, upper extremity, baseball, pitcher, throwing, and muscle activity. Inclusion criteria consisted of original research articles in the English language involving healthy athletes, use of fatigue protocols, and the evaluation of at least 1 upper limb biomechanical variable.

Results

A total of 35 studies involving 644 athletes (90 females, 554 males; mean age, 20.2 years) met the inclusion criteria. General fatigue protocols were used in 2 investigations, peripheral protocols were used in all 35 studies, and 5 different athletic tasks were studied (simulated baseball game, overhead throwing, high-effort swimming, simulated tennis game, and overhead serving). There was a uniform decrease in muscle force production and proprioception in athletes after completing a fatigue protocol. However, there was no consistency among studies when evaluating other important upper limb biomechanical factors. The fatigue protocols did not consistently produce statistically significant changes in elbow torque, pitching biomechanics, or ball velocity.

Conclusion

A uniform decrease in muscle force production and proprioception was found after fatigue protocols; however, a majority of fatigue protocols published in the current literature are inconsistently measured and produce heterogeneous results. Therefore, currently, no recommendations can be made for changes in UCL injury prevention training programs to account for potential effects of fatigue. The effect of muscle force production and proprioception on upper extremity injuries should be evaluated in future studies.

Lactotripeptides Supplementations Alleviate the Decrease in Maximal Isometric Force After High-Intensity Eccentric Exercise: A Randomized, Placebo-Controlled, Double-Blind Clinical Trial

OBJECTIVE

The aim of the study was to investigate whether lactotripeptides supplementations alleviate the decrease in the maximal isometric force, an indirect marker of muscle damage, after eccentric exercise (ECC).

DESIGN

Twenty-two young men performed 50 ECC of the elbow flexors using an isokinetic dynamometer. The subjects were randomly assigned to either the placebo or lactotripeptides group and were each given a 4.5 mg/d placebo or lactotripeptides thrice on the exercise day and the day after. Maximal isometric force and brachial arterial diameter were assessed before and 2 days after the ECC.

RESULTS

The interaction of time and group on maximal isometric force was significant (P < 0.05); maximal isometric force was significantly decreased in both groups after ECC (P < 0.005). The interaction of brachial arterial diameter was significant (P < 0.05); brachial arterial diameter was significantly increased in only the lactotripeptides group (P < 0.005). In addition, the change in maximal isometric force was significantly related to the change in brachial arterial diameter after adjusting for body weight and change in range of motion (P < 0.05).

CONCLUSIONS

The present results suggest that lactotripeptides supplementation alleviates the decrease in the maximal isometric force via an increase in brachial arterial diameter after ECC.

Neuromuscular changes and the rapid adaptation following a bout of damaging eccentric exercise

INTRODUCTION

An initial bout of eccentric exercise is known to protect against muscle damage following a repeated bout of the same exercise; however, the neuromuscular adaptations owing to this phenomenon are unknown.

AIM

To determine whether neuromuscular disturbances are modulated following a repeated bout of eccentric exercise.

METHODS

Following eccentric exercise performed with the elbow flexors, we measured maximal voluntary force, resting twitch force, muscle soreness, creatine kinase (CK) and voluntary activation (VA) using motor point and motor cortex stimulation at baseline, immediately post-exercise and at 1, 2, 3, 4 and 7 days post-exercise on two occasions, separated by 3 weeks.

RESULTS

Significant muscle damage and fatigue were evident following the first exercise bout; maximal voluntary contraction (MVC) was reduced immediately by 35% and remained depressed at 7 days post-exercise. Soreness and CK release peaked at 3 and 4 days post-exercise respectively. Resting twitch force remained significantly reduced at 7 days (-48%), whilst VA measured with motor point and motor cortex stimulation was reduced until 2 and 3 days respectively. A repeated bout effect (RBE) was observed with attenuated soreness and CK release and a quicker recovery of MVC and resting twitch force. A similar decrement in VA was observed following both bouts; however, following the repeated bout there was a significantly smaller reduction in, and a faster recovery of, VA measured using motor cortical stimulation.

CONCLUSION

Our data suggest that the RBE may be explained, partly, by a modification in motor corticospinal drive.

Acute changes in glenohumeral range-of-motion following in-season minor league pitching starts

BACKGROUND

Asymmetric glenohumeral range-of-motion (ROM) between the throwing and non-throwing arms of overhead athletes has been well described in the literature. Thresholds of internal rotation (IR) loss have been associated with throwing arm injury in baseball players. Acute changes in shoulder ROM following an individual pitching appearance remain poorly understood.

OBJECTIVES

To determine the acute change of external rotation (ER), IR, and total arc-of-motion (TAM) in minor league starting pitchers immediately following an in-season starting pitching appearance.

METHODS

Nine minor league starting pitchers participated in the study with data collected for 22 individual starts. IR, ER and TAM were measured in the throwing shoulder and non-throwing shoulder at three time points for each appearance: before, immediately following, and at 24 hours following the pitching appearance.

RESULTS

In the throwing arm, IR significantly decreased (49.4 vs 46.0, p = 0.037) immediately after pitching, and ER significantly increased immediately following an appearance (150.7 vs 153.6, p = 0.030) and at 24 hours (150.7 vs 154.0, p = 0.028). No difference was detected in throwing arm TAM and IR at 24 hours, or TAM immediately following an appearance.

CONCLUSIONS

Minor league pitchers demonstrate the dynamic glenohumeral ROM changes after starting appearances of increased ER and diminished IR with maintenance of TAM. At 24 hours, the observed loss of IR had resolved, whereas the gains in ER remained present. Our study supports the need to further assess the acute changes of glenohumeral ROM in pitchers, and the association of acute glenohumeral ROM change with the development of pathologic ROM profiles and injury.

Effects of phonophoresis and gold nanoparticles in experimental model of muscle overuse: role of oxidative stress

The aim of the study described here was to investigate the effects of pulsed ultrasound and gold nanoparticles (AuNPs) on behavioral, inflammatory and oxidative stress parameters in an experimental model of overuse. Wistar rats performed 21 d of exercise on a treadmill at different intensities and were exposed to ultrasound in the presence or absence of AuNPs. The overuse model promoted behavioral changes and increased creatine kinase, superoxide dismutase and glutathione peroxidase activity, as well as the levels of superoxide, nitrotyrosine, nitric oxide, thiobarbituric acid reactive substance, carbonyl, tumor necrosis factor α and interleukin-6. These values were significantly decreased by AuNPs and by AuNPs plus ultrasound. Catalase activity remained unchanged and the glutathione level increased significantly after exposure to AuNPs plus ultrasound. These results suggest a susceptibility to anxiety as well as elevated levels of oxidative stress. However, therapeutic interventions with AuNPs plus ultrasound reduced the production of oxidants and oxidative damage and improved the anti-oxidant defense system.

Changes in force and stiffness after static stretching of eccentrically-damaged hamstrings

PURPOSE

This study compared responses to static stretching between eccentrically damaged and non-damaged muscles.

METHODS

Twelve young men performed 60 maximum knee flexor eccentric contractions of one leg, and received a 300-s continuous passive static stretching at tolerable intensity without pain to both knee flexors at 2 and 4 days after the eccentric exercise. Range of motion (ROM) and passive stiffness during knee extension, passive torque at onset of pain (PT), maximum voluntary isometric (MVC-ISO) and isokinetic concentric contraction torque (MVC-CON), and visual analogue scale (VAS) for muscle soreness were measured before, immediately after, 60 min, 2 and 4 days after exercise as well as before, immediately after, 20 and 60 min after the stretching. Changes in these variables after eccentric exercise and stretching were compared between limbs.

RESULTS

The eccentric exercise decreased MVC-ISO, MVC-CON, ROM and PT, and increased passive stiffness and VAS (p < 0.05), suggesting that muscle damage was induced to the knee flexors. ROM and PT increased after stretching for both limbs; however, the magnitude of the increase was greater (p < 0.05) for the damaged than non-damaged limb. Passive stiffness decreased for both limbs similarly (4-7 %) at immediately after stretching (p < 0.05). Significant decreases in MVC-ISO torque (7-11 %) after stretching were observed only for the non-damaged limb (p < 0.05), but MVC-CON torque did not change after stretching for both limbs. VAS decreased for the exercised limb after stretching (p < 0.05).

CONCLUSIONS

These results suggest that the static stretching at tolerable intensity without pain produced greater positive effects on damaged than non-damaged muscles.

Use it or lose it: multiscale skeletal muscle adaptation to mechanical stimuli

Skeletal muscle undergoes continuous turnover to adapt to changes in its mechanical environment. Overload increases muscle mass, whereas underload decreases muscle mass. These changes are correlated with, and enabled by, structural alterations across the molecular, subcellular, cellular, tissue, and organ scales. Despite extensive research on muscle adaptation at the individual scales, the interaction of the underlying mechanisms across the scales remains poorly understood. Here, we present a thorough review and a broad classification of multiscale muscle adaptation in response to a variety of mechanical stimuli. From this classification, we suggest that a mathematical model for skeletal muscle adaptation should include the four major stimuli, overstretch, understretch, overload, and underload, and the five key players in skeletal muscle adaptation, myosin heavy chain isoform, serial sarcomere number, parallel sarcomere number, pennation angle, and extracellular matrix composition. Including this information in multiscale computational models of muscle will shape our understanding of the interacting mechanisms of skeletal muscle adaptation across the scales. Ultimately, this will allow us to rationalize the design of exercise and rehabilitation programs, and improve the long-term success of interventional treatment in musculoskeletal disease.

Effects of eccentric training on mechanical properties of the plantar flexor muscle-tendon complex

Eccentric training is a mechanical loading classically used in clinical environment to rehabilitate patients with tendinopathies. In this context, eccentric training is supposed to alter tendon mechanical properties but interaction with the other components of the muscle-tendon complex remains unclear. The aim of this study was to determine the specific effects of 14 wk of eccentric training on muscle and tendon mechanical properties assessed in active and passive conditions in vivo. Twenty-four subjects were randomly divided into a trained group (n = 11) and a control group (n = 13). Stiffness of the active and passive parts of the series elastic component of plantar flexors were determined using a fast stretch during submaximal isometric contraction, Achilles tendon stiffness and dissipative properties were assessed during isometric plantar flexion, and passive stiffness of gastrocnemii muscles and Achilles tendon were determined using ultrasonography while ankle joint was passively moved. A significant decrease in the active part of the series elastic component stiffness was found (P < 0.05). In contrast, a significant increase in Achilles tendon stiffness determined under passive conditions was observed (P < 0.05). No significant change in triceps surae muscles and Achilles tendon geometrical parameters was shown (P > 0.05). Specific changes in muscle and tendon involved in plantar flexion are mainly due to changes in intrinsic mechanical properties of muscle and tendon tissues. Specific assessment of both Achilles tendon and plantar flexor muscles allowed a better understanding of the functional behavior of the muscle-tendon complex and its adaptation to eccentric training.

Myometry revealed medication-induced decrease in resting skeletal muscle stiffness in Parkinson's disease patients

BACKGROUND

Based on combined analysis of clinical assessment of parkinsonian rigidity (constant resistance force generated during passive movement in a joint), electromyography and/or dynamometry many studies showed objectively that anti-parkinsonian medication decreases the rigidity in Parkinson's disease (PD). Rigidity-related changes in resting muscle stiffness (changed muscle's mechanical property related to its structural changes and changed neural drive) in PD patients have been revealed by myometry, a simple, sensitive, and reliable method for measuring mechanical properties in human soft tissues. However, an application of myometry in estimation of medication effects on the PD rigidity-related muscle stiffness has not been reported yet. Therefore, our study aimed to assess medication-induced changes in resting muscle stiffness in PD patients using myometry.

METHODS

We measured resting muscle stiffness by myometry and recorded a surface electromyogram of relaxed biceps brachii, brachioradialis and triceps brachii muscles in ten patients with PD (age: 51-80 years; Hoehn and Yahr stage: 2.5-4) during medication on-phase (when subjects felt best comfort and fitness after medication: Levodopa, Piribedil, Ropinirol) and medication off-phase (12h after withdrawal of the medication).

FINDINGS

Our patients had significantly lower myometric stiffness and electromyogram amplitude in all tested muscles, and also lower clinical rigidity scores during the medication on-phase compared with the medication off-phase.

INTERPRETATION

Myometry revealed that anti-parkinsonian medication decreases not only rigidity in PD, but also rigidity-related stiffness in resting skeletal muscles in PD patients. These findings show that myometry can enrich neurological practice, by allowing objective and reliable assessment of parkinsonian rigidity treatment effectiveness.

Quadriceps muscle tone, elasticity and stiffness in older males: reliability and symmetry using the MyotonPRO

BACKGROUND

The MyotonPRO (Myoton Ltd; London) is a new portable device for measuring muscle mechanical properties (e.g. tone) and its reliability has yet to be established. Little is known about between-limb symmetry of mechanical properties in healthy older people, despite symmetry often being used as a measure of unilateral abnormalities in clinical assessment. Since quadriceps is important for mobility, it was selected for the present study.

AIMS

To investigate: (i) between-day intra-rater reliability of a novice user of MyotonPRO; (ii) between-side symmetry of mechanical properties of quadriceps in older males.

METHODS

Twenty healthy, community dwelling, right-lower-limb-dominant males (mean age 71.7, range 65-82 years) were studied. With the participant in relaxed supine lying, the MyotonPRO applied two consecutive sets of 10 taps to induce muscle oscillations of rectus femoris, from which measurements of decrement (elasticity), frequency (tone), and stiffness were obtained. Tests were performed on two occasions at the same time and day of the week, one week apart.

RESULTS

Repeated measurements had very high within-day (intraclass correlation coefficient, ICC 3,1>0.90) and high between-day (ICC 3,2>0.70; mean of two measurement sets) reliability. There was no statistically significant difference between muscle mechanical properties of the dominant and non-dominant muscles (<2.5% difference; p>0.05), thereby indicating symmetry.

CONCLUSIONS

High intra-rater reliability was established for MyotonPRO measurements of quadriceps in healthy older males, which were symmetrical between sides. These findings indicate that larger studies are warranted to establish normal reference ranges of data with which to compare patients with muscle abnormalities.