Effect of delayed-onset muscle soreness on muscle recovery after a fatiguing isometric contraction

A Novel Mechanomyography (MMG) Sensor Based on Piezo-Resistance Principle and with a Pyramidic Microarray

Flexible piezoresistive sensors built by printing nanoparticles onto soft substrates are crucial for continuous health monitoring and wearable devices. In this study, a mechanomyography (MMG) sensor was developed using a flexible piezoresistive MMG signal sensor based on a pyramidal polydimethylsiloxane (PDMS) microarray sprayed with carbon nanotubes (CNTs). The experiment was conducted, and the results show that the sensitivity of the sensor can reach 0.4 kPa-1 in the measurement range of 0~1.5 kPa, and the correlation reached 96%. This has further implications for the possibility that muscle activation can be converted into mechanical movement. The integrity of the sensor in terms of its MMG signal acquisition was tested based on five subjects who were performing arm bending and arm extending movements. The results of this test were promising.

A New Approach to Noninvasive-Prolonged Fatigue Identification Based on Surface EMG Time-Frequency and Wavelet Features

In sports, fatigue management is vital as adequate rest builds strength and enhances performance, whereas inadequate rest exposes the body to prolonged fatigue (PF) or also known as overtraining. This paper presents PF identification and classification based on surface electromyography (EMG) signals. An experiment was performed on twenty participants to investigate the behaviour of surface EMG during the inception of PF. PF symptoms were induced in accord with a five-day Bruce Protocol treadmill test on four lower extremity muscles: the biceps femoris (BF), rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL). The results demonstrate that the experiment successfully induces soreness, unexplained lethargy, and performance decrement and also indicate that the progression of PF can be observed based on changes in frequency features (ΔF _med and ΔF _mean) and time features (ΔRMS and ΔMAV) of surface EMG. This study also demonstrates the ability of wavelet index features in PF identification. Using a naïve Bayes (NB) classifier exhibits the highest accuracy based on time and frequency features with 98% in distinguishing PF on RF, 94% on BF, 9% on VL, and 97% on VM. Thus, this study has positively indicated that surface EMG can be used in identifying the inception of PF. The implication of the findings is significant in sports to prevent a greater risk of PF.

Effect of Resonant Frequency Vibration on Delayed Onset Muscle Soreness and Resulting Stiffness as Measured by Shear-Wave Elastography

This study utilized resonant frequency vibration to the upper body to determine changes in pain, stiffness and isometric strength of the biceps brachii after eccentric damage. Thirty-one participants without recent resistance training were randomized into three groups: a Control (C) group and two eccentric exercise groups (No vibration (NV) and Vibration (V)). After muscle damage, participants in the V group received upper body vibration (UBV) therapy for 5 min on days 1-4. All participants completed a visual analog scale (VAS), maximum voluntary isometric contraction (MVIC), and shear wave elastography (SWE) of the bicep at baseline (pre-exercise), 24 h, 48 h, and 1-week post exercise. There was a significant difference between V and NV at 24 h for VAS (p = 0.0051), at 24 h and 1-week for MVIC (p = 0.0017 and p = 0.0016, respectively). There was a significant decrease in SWE for the V group from 24-48 h (p = 0.0003), while there was no significant change in the NV group (p = 0.9341). The use of UBV resonant vibration decreased MVIC decrement and reduced VAS pain ratings at 24 h post eccentric damage. SWE was strongly negatively correlated with MVIC and may function as a predictor of intrinsic muscle state in the time course of recovery of the biceps brachii.

Men and women show different adaptations of quadriceps activity following fatiguing contractions: An explanation for the increased incidence of sports-related knee injuries in women?

We investigated whether adaptations of quadriceps muscle activity to fatiguing exercise differs between sexes. Fifteen healthy men (age, mean ± SD; 22. ± 2.4 yr, body mass 70.5 ± 11.4 kg, height 1.72 ± 0.06 m) and 15 healthy women (age, mean ± SD; 21 ± 1.8 yr, body mass 60 ± 7.5 kg, height 1.62 ± 0.07 m), all right leg dominant, participated in the study. Participants performed a submaximal isometric knee extension contraction at 50% of the maximum voluntary contraction (MVC) sustained until task failure before and after a fatiguing exercise. Surface electromyography (EMG) was simultaneously recorded from nine regions distributed over the medial, middle and lateral locations of the quadriceps muscles in a longitudinal direction corresponding to the vastus medialis, rectus femoris (RF) and vastus lateralis muscle, respectively. A significant reduction in maximal force and time to task failure were observed after fatiguing exercise for both sexes (P < 0.001). However, women displayed greater myoelectric manifestations of fatigue specifically for the RF during the post-fatigue sustained contraction (P < 0.05). The RF is more susceptible to fatiguing exercise in women compared to men which may partly explain the higher risk of knee injuries among female athletes during competitive sports.

Whole-Body Vibration as a Warm-up Before Exercise-Induced Muscle Damage on Symptoms of Delayed-Onset Muscle Soreness in Trained Subjects

Magoffin, RD, Parcell, AC, Hyldahl, RD, Fellingham, GW, Hopkins, JT, and Feland, JB. Whole-body vibration as a warm-up before exercise-induced muscle damage on symptoms of delayed-onset muscle soreness in trained subjects. J Strength Cond Res 34(4): 1123-1132, 2020-There is no clear scientific evidence that whole-body vibration (WBV) used as a warm-up before performing eccentric exercise mitigates delayed-onset muscle soreness (DOMS) and speeds strength loss recovery. These benefits were observed primarily in nonresistance-trained individuals. The aim of this study was to determine whether WBV could mitigate soreness and expedite strength recovery for resistance-trained individuals when used as a warm-up before eccentric exercise. Thirty resistance-trained males completed 300 maximal eccentric contractions of the quadriceps after warming up with (WBV) or without (CON) WBV. Both CON and WBV experienced significant isometric (26.3 and 30.2%, respectively) and dynamic (50.9 and 46.4%, respectively) strength loss immediately after exercise. Isometric strength was significantly depressed after 24 hours in the CON group (8.2% p < 0.02), but not in the WBV group (5.9% p = 0.7). Isometric strength was no longer significantly depressed after 48 hours in the CON group (6.1% p < 0.07) or the WBV group (4.1% p = 0.20). Dynamic strength was significantly decreased in both the CON and WBV groups at 24 hours (17.7% p < 0.001 and 15.5% p < 0.001, respectively) and 48 hours (17.1% p < 0.01 and 13.6% p < 0.002), but only significant for the CON at 1 week after exercise (8.6% p = 0.05). Pain as measured by a visual analog scale was significant in both groups at 24 and 48 hours after exercise, but WBV experienced significantly less soreness than the CON group after 24 hours (28 vs. 46 mm p < 0.01, respectively) and 48 hours (38 vs. 50 mm p < 0.01). Pain pressure threshold increased significantly in both groups, but there was no difference between groups. These results suggest the use of WBV before eccentric exercise mildly mitigates DOMS in trained individuals. Application of WBV can function as a quick mode of warm-up before resistance training and can decrease pain perception from DOMS. This may be beneficial to athletes undergoing a heavy strength training phase where DOMS is likely.

Muscle fiber conduction velocity of the vastus medilais and lateralis muscle after eccentric exercise induced-muscle damage

Change in muscle fiber conduction velocity (MFCV) has been reported after eccentric exercise induces muscle fiber damage, most likely due to a change in membrane permeability of the injured fiber. The extent of damage to the muscle fiber depends on the morphological and architectural characteristics of the muscle fibers. Morphological and architectural characteristics of the VMO muscle fibers are different from VL muscle. Thus, it is expected that eccentric exercise of quadriceps muscle results in a non-uniform fiber damage within the VMO and VL muscle and, as a consequence, non-uniform changes in membrane excitability and conduction velocity. The aim of the study was to investigate MFCV of the VMO and VL muscles before and 24 h after eccentric exercise. Multichannel surface EMG signals were concurrently recorded from the right VMO and VL muscles of 15 healthy men during sustained isometric contractions at 50% of the maximal force. Maximal voluntary force significantly reduced after eccentric exercise with respect to the pre-exercise condition (P < 0.0001). MFCV decreased over time during the sustained contractions at faster rates when assessed 24 h after exercise (VMO = -26.1; VL = -20.1) with respect to the pre-exercise condition (VMO = -9.1; VL = -13.7, P < 0.0001). Moreover, VMO showed a greater rate of reduction in MFCV over sustained contraction (26.1 ± 10.7%) in comparison with VL muscle (20.1 ± 8.5%, P < 0.025) 24 h after eccentric exercise. The result indicates that eccentric exercise contributes to a larger reduction in MFCV within the VMO muscle as compared to the VL muscle. This may abolish the ability of VMO to counteract the lateral pull of the VL muscle during knee extension, thereby leaving the knee complex more vulnerable to injury.

Minimal Evidence for a Secondary Loss of Strength After an Acute Muscle Injury: A Systematic Review and Meta-Analysis

BACKGROUND

An immediate loss of strength follows virtually all types of muscle injury but there is debate whether the initial strength loss is maximal or if a secondary loss of strength occurs during the first 3 days post-injury.

OBJECTIVE

The objective of this analysis was to conduct a systematic review and meta-analysis of the research literature to determine if a secondary loss of strength occurs after an injurious initiating event.

METHODS

Literature searches were performed using eight electronic databases (e.g., PubMed, Cochrane Library). Search terms included skeletal muscle AND (injur* OR damage*) AND (strength OR force OR torque). The extracted strength data were converted to a standard format by calculating the standardized mean difference, which is reported as the effect size (ES) along with its 95 % confidence interval (CI). The calculation of ES was designed so that a negative ES that was statistically less than zero would be interpreted as indicating a secondary loss of strength.

RESULTS

A total of 223 studies with over 4000 human and animal subjects yielded data on 262 independent groups and a total of 936 separate ESs. Our overall meta-analysis yielded a small-to-medium, positive overall ES that was statistically greater than zero (overall ES = +0.34, 95 % CI 0.27-0.40; P < 0.00000001). Considerable variation in ES was observed among studies (I ² = 86 %), which could be partially explained by the research group conducting the study, sex of the subject, day of post-injury strength assessment, whether fatigue was present immediately post-injury, and the muscle group injured. From the subgroup meta-analyses probing these variables, 36 subgroup ESs were calculated and none were statistically less than zero.

CONCLUSION

Overall, our findings do not support the presence of a secondary loss of strength following an acute muscle injury, and strongly suggest that strength, on average, recovers steadily over the first 3 days post-injury.

Physiological and Neural Adaptations to Eccentric Exercise: Mechanisms and Considerations for Training

Eccentric exercise is characterized by initial unfavorable effects such as subcellular muscle damage, pain, reduced fiber excitability, and initial muscle weakness. However, stretch combined with overload, as in eccentric contractions, is an effective stimulus for inducing physiological and neural adaptations to training. Eccentric exercise-induced adaptations include muscle hypertrophy, increased cortical activity, and changes in motor unit behavior, all of which contribute to improved muscle function. In this brief review, neuromuscular adaptations to different forms of exercise are reviewed, the positive training effects of eccentric exercise are presented, and the implications for training are considered.

Delayed onset of vastii muscle activity in response to rapid postural perturbations following eccentric exercise: a mechanism that underpins knee pain after eccentric exercise?

BACKGROUND

Appropriate timing of activity of the vastus medialis obliqus (VMO) and vastus lateralis (VL) muscles is a key factor for proper tracking of the patella in the trochlear groove during knee extension. This study investigates the relative timing of activation of the VMO and VL muscles during unexpected perturbations performed before and after eccentric exercise.

METHODS

Surface electromyography signals were recorded from the VMO and VL muscles of the right leg in 11 healthy men during rapid postural perturbations performed at baseline, immediately after eccentric exercise of the quadriceps, and at 24 and 48 h after exercise. Participants stood on a moveable platform during which eight randomised postural perturbations were performed (4 repetitions of 2 perturbation types: 8 cm forward slides, 8 cm backward slides).

RESULTS

Before the eccentric exercise, the onset of VMO activity was significantly earlier than the VL muscle (average for both forward and backward perturbations: VMO 39.0±7.1 ms; VL 43.7±7.9 ms). However, the onset of VMO activity was significantly later compared with VL muscle immediately after eccentric exercise and this remained 24 and 48 h after eccentric exercise (average across all postexercise sessions and perturbation directions: VMO 72.3±11.1 ms; VL 56.0±8.2 ms; p<0.05).

CONCLUSIONS

The onset of VMO-VL activity in response to rapid destabilising perturbations is altered immediately after eccentric exercise and during eccentric exercise-induced muscle soreness up to 48 h later. These observations may help explain the high prevalence of knee disorders after high intensity eccentric exercise.

Unilateral eccentric exercise of the knee flexors affects muscle activation during gait

Uni-lateral muscle soreness is common yet the effects on gait or electromyographic (EMG) activity are unknown. The purpose of our study was to induce delayed onset muscle soreness (DOMS) in the knee flexor group and measure the resultant change in EMG activity and knee motion during gait. Nine healthy subjects participated in the study. Measures of function, evoked tenderness of the biceps femoris, as well as knee angle, and EMG activity during gait were assessed prior and 48 h after an eccentric exercise protocol. DOMS was induced unilaterally in the knee flexors using an isokinetic dynamometer and subjects exercised until they could not generate 50% of their maximal voluntary isometric contraction (MVIC). There was a significant decrease in biceps femoris activity after DOMS during the last phase of gait. Moreover, there was a day × phase interaction for gastrocnemius activity with the last two phases displaying an increase in activity. There was no significant change in knee angle during gait. The decrease in biceps femoris activity as well as the increase in gastrocnemius activity could be evidence of a protective mechanism designed to decrease activity of the sore muscle while increasing the activity of a synergistic muscle.

Non-uniform muscle adaptations to eccentric exercise and the implications for training and sport

Due to the variations in morphological and architectural characteristics of fibers within a skeletal muscle, regions of a muscle may be differently affected by eccentric exercise. Although eccentric exercise may be beneficial for increasing muscle mass and can be beneficial for the treatment of tendinopathies, the non-uniform effect of eccentric exercise results in regional muscle damage and as a consequence, non-uniform changes in muscle activation. This regional muscle weakness can contribute to muscle strength imbalances and may potentially alter the load distribution on joint structures, increasing the risk of injury. In this brief review, the non-uniform effects of eccentric exercise are reviewed and their implications for training and sport are considered.

Eccentric exercise and delayed onset muscle soreness of the quadriceps induce adjustments in agonist-antagonist activity, which are dependent on the motor task

This study investigates the effects of eccentric exercise and delayed onset muscle soreness (DOMS) of the quadriceps on agonist–antagonist activity during a range of motor tasks. Ten healthy volunteers (age, mean ± SD, 24.9 ± 3.2 years) performed maximum voluntary contractions (MVC) and explosive isometric contractions of the knee extensors followed by isometric contractions at 2.5, 5, 10, 15, 20, and 30% MVC at baseline, immediately after and 24 h after eccentric exercise of the quadriceps. During each task, force of the knee extensors and surface EMG of the vasti and hamstrings muscles were recorded concurrently. Rate of force development (RFD) was computed from the explosive isometric contraction, and the coefficient of variation of the force (CoV) signal was estimated from the submaximal contractions. Twenty-four hours after exercise, the subjects rated their perceived pain intensity as 4.1 ± 1.2 (score out of 10). The maximum RFD and MVC of the knee extensors was reduced immediately post- and 24 h after eccentric exercise compared to baseline (average across both time points: 19.1 ± 17.1% and 11.9 ± 9.8% lower, respectively, P < 0.05). The CoV for force during the submaximal contractions was greater immediately after eccentric exercise (up to 66% higher than baseline, P < 0.001) and remained higher 24 h post-exercise during the presence of DOMS (P < 0.01). For the explosive and MVC tasks, the EMG amplitude of the vasti muscles decreased immediately after exercise and was accompanied by increased antagonist EMG for the explosive contraction only. On the contrary, reduced force steadiness was accompanied by a general increase in EMG amplitude of the vasti muscles and was accompanied by increased antagonist activity, but only at higher force levels (>15% MVC). This study shows that eccentric exercise and subsequent DOMS of the quadriceps reduce the maximal force, rate of force development and force steadiness of the knee extensors, and is accompanied by different adjustments of agonist and antagonist muscle activities.

Delayed-onset muscle soreness alters the response to postural perturbations

INTRODUCTION

Eccentric contractions induce muscle fiber damage that is associated with delayed-onset muscle soreness and an impaired ability of the muscle to generate voluntary force. Pain and pathophysiological changes within the damaged muscle can delay or inhibit neuromuscular responses at the injured site, which is expected to have an effect on reflex activity of the muscle.

PURPOSE

The aim of the study was to investigate the reflex activity of knee muscles to rapid destabilizing perturbations, before, immediately after, and 24 and 48 h after eccentric exercise.

METHODS

Bipolar surface EMG signals were recorded from 10 healthy men with seven pairs of electrodes located on the knee extensor muscles (vastus medialis, rectus femoris, and vastus lateralis) and knee flexor muscles (the medial and lateral heads of the hamstring and the medial and lateral heads of gastrocnemius) of the right leg during rapid perturbations.

RESULTS

The maximal voluntary contraction force decreased by 24% ± 4.9% immediately after exercise and remained reduced by 21.4% ± 4.1% at 24 h and by 21.6% ± 9.9% at 48 h after exercise with respect to baseline. During the postexercise postural perturbations, the EMG average rectified value of the knee extensor muscles was significantly lower than baseline (P < 0.001). Moreover, the decrease in average rectified value over time during postexercise sustained contractions was greatest compared with the session before exercise (P < 0.0001).

CONCLUSIONS

Reflex activity in leg muscles elicited by rapid destabilizing perturbations is reduced after exercise-induced muscle soreness.