Pain quality patterns in delayed onset muscle soreness of the lower back suggest sensitization of fascia rather than muscle afferents: a secondary analysis study.

Delayed onset muscle soreness (DOMS) of the lower back is considered a surrogate for acute low back pain (aLBP) in experimental studies. Of note, it is often unquestioningly assumed to be muscle pain. To date, there has not been a study analyzing lumbar DOMS in terms of its pain origin, which was the aim of this study. Sixteen healthy individuals (L-DOMS) were enrolled for the present study and matched to participants from a previous study (n = 16, L-PAIN) who had undergone selective electrical stimulation of the thoracolumbar fascia and the multifidus muscle. DOMS was induced in the lower back of the L-DOMS group using eccentric trunk extensions performed until exhaustion. On subsequent days, pain on palpation (100-mm analogue scale), pressure pain threshold (PPT), and the Pain Sensation Scale (SES) were used to examine the sensory characteristics of DOMS. Pain on palpation showed a significant increase 24 and 48 h after eccentric training, whereas PPT was not affected (p > 0.05). Factor analysis of L-DOMS and L-PAIN sensory descriptors (SES) yielded a stable three-factor solution distinguishing superficial thermal ("heat pain ") from superficial mechanical pain ("sharp pain") and "deep pain." "Heat pain " and "deep pain" in L-DOMS were almost identical to sensory descriptors from electrical stimulation of fascial tissue (L-PAIN, all p > 0.679) but significantly different from muscle pain (all p < 0.029). The differences in sensory description patterns as well as in PPT and self-reported DOMS for palpation pain scores suggest that DOMS has a fascial rather than a muscular origin.

Changes in nerve growth factor in vastus lateralis muscle after the first versus second bout of one-leg eccentric cycling.

Delayed onset muscle soreness (DOMS) develops after performing unaccustomed eccentric exercises. Animal studies have shown that DOMS is mechanical hyperalgesia through nociceptor sensitization induced by nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF) upregulated by cyclooxygenase-2 (COX-2). However, no previous study has investigated these in relation to DOMS in humans. This study compared the first and second bouts of one-leg eccentric cycling (ECC) for changes in NGF, GDNF, and COX-2 mRNA in the vastus lateralis (VL). Seven healthy adults (18-40 years) performed two bouts of ECC (10 sets of 50 contractions) with 80% maximal voluntary concentric peak torque separated by 2 weeks (ECC1, ECC2). Muscle soreness that was assessed by a visual analog scale and maximal voluntary isometric contraction (MVC) torque of the knee extensors were measured before, immediately after (MVC only), 24 and 48 h post-exercise. Muscle biopsy was taken from the VL before the first bout from nonexercised leg (control) and 24 h after each bout from the exercised leg, and analyzed for NGF, GDNF, and COX-2 mRNA. Peak DOMS was more than two times greater and MVC torque at 48 h post-exercise was approximately 20% smaller after ECC1 than ECC2 (p < 0.05), suggesting the repeated bout effect. NGF mRNA level was higher (p < 0.05) post-ECC1 (0.79 ± 0.68 arbitrary unit) than control (0.06 ± 0.07) and post-ECC2 (0.08 ± 0.10). GDNF and COX-2 mRNA did not show significant differences between control, post-ECC1, and post-ECC2. These results suggest that an increase in NGF is associated with the development of DOMS in humans.

Impact of curcumin supplementation on exercise performance and muscle damage after a soccer match: a double-blind placebo-controlled cross-over study.

PURPOSE: Curcumin ingestion can mitigate muscle damage, soreness, and inflammation following a laboratory-based eccentric exercise. Similar effects were observed in recent field-based studies wherein responses were evaluated after a soccer match. However, various potential confounding factors, such as matching opponent skill levels and daily training conditions, may have influenced the outcomes. In the present study, we investigated whether curcumin intake ameliorates changes in muscle damage markers following a soccer match while controlling for the potential confounding factors. METHODS: Fifteen collegiate athletes were tested in a randomized, double-blind, cross-over manner. They were recruited from the same college soccer team and thus followed the same daily training regimen and competition levels. Furthermore, athletes positioning during matches were counterbalanced. They consumed either 180 mg/day of curcumin or a placebo starting 1 h before the match and continuing for 2 days after a match (two 45-min plays and a 15-min half-time). Muscle soreness, jump performance (including countermovement jump and rebound jump index), and inflammatory and muscle damage markers (high-sensitive C-reactive protein, serum creatine kinase activity, and urinary N-terminal fragment of titin concentration) were evaluated before and after the match. The washout period between matches was set at 1 week. RESULTS: After the match, all markers showed similarity between the placebo and curcumin conditions (all P > 0.208). CONCLUSION: These findings indicate that ingesting 180 mg/day of curcumin may not expedite recovery from muscle damage elicited by soccer matches in collegiate soccer players.

Downhill running increases markers of muscle damage and impairs the maximal voluntary force production as well as the late phase of the rate of voluntary force development.

PURPOSE: To examined the time-course of the early and late phase of the rate of voluntary force development (RVFD) and muscle damage markers after downhill running. METHODS: Ten recreational runners performed a 30-min downhill run at 10 km h-1 and -20% (-11.3°) on a motorized treadmill. At baseline and each day up to 4 days RVFD, knee extensors maximum voluntary isometric force (MVIC), serum creatine kinase (CK) concentration, quadriceps swelling, and soreness were assessed. The early (0-50 ms) and late (100-200 ms) phase of the RVFD, as well as the force developed at 50 and 200 ms, were also determined. RESULTS: MVIC showed moderate decrements (p < 0.05) and recovered after 4 days (p > 0.05). Force at 50 ms and the early phase were not impaired (p > 0.05). Conversely, force at 200 ms and the late phase showed moderate decrements (p < 0.05) and recovered after 3 and 4 days, respectively (p > 0.05). CK concentration, quadriceps swelling, and soreness increased (p < 0.05) were overall fully resolved after 4 days (p > 0.05). CONCLUSION: Downhill running affected the knee extensors RVFD late but not early phase. The RVFD late phase may be used as an additional marker of muscle damage in trail running.

Effect of different Volumes of exercise on skin temperature responses over the following 24 hours.

Skin temperature responses have been advocated to indicate exercise-induced muscle soreness and recovery status. While the evidence is contradictory, we hypothesize that the presence of muscle damage and the time window of measurement are confounding factors in the skin temperature response. The objective was to determine whether skin temperature is influenced by different workloads and the time course of temperature measurements over the following 24 h. 24 trained male military were assigned to one of three groups: GC group (n = 8) serving as control not performing exercises, GE group (n = 8) performing a simulated military combat protocol in an exercise track with different obstacles but designed not to elicit muscle damage, and the GEMD group (n = 8) performing the simulated military combat protocol plus 5 sets of 20 drop jumps, with 10-sec between repetitions and with 2-min of rest between sets aiming to induce muscle damage. Skin temperature was measured using infrared thermography before exercise (Pre) and 4 (Post4h), 8 (Post8h) and 24h (Post24h) post-exercise. Perception of pain (DOMS) was evaluated Pre, Post24h, and Post48h, and countermovement jump height was evaluated at Pre and Post24h. DOMS did not differ between groups in the Pre and Post24h measures but GEMD presented higher DOMS than the other groups at Post48h (p < 0.001 and large effect size). Jump height did not differ for GEMD and GC, and GE presented higher jump height at Post24h than GC (p = 0.02 and large effect size). Skin temperature responses of GEMD and GG were similar in all measurement moments (p > 0.22), and GE presented higher skin temperature than the GC and the GEMD groups at Post24h (p < 0.01 and large effect sizes). In conclusion, although physical exercise elicits higher skin temperature that lasts up to 24 h following the efforts, muscle soreness depresses this response.

Effects of ischaemic post-conditioning on eccentric exercise-induced muscle damage.

Exercise-induced muscle damage (EIMD) is a common phenomenon resulting from high-intensity exercise that impairs subsequent performance. Ischaemic post-conditioning (IPOC) is a simple intervention that has been shown to reduce muscle damage after prolonged ischaemia, a condition mechanistically similar to EIMD. The purpose of this study was to determine whether IPOC could alleviate muscle damage after eccentric exercise. Thirty-two young male participants were randomized into either a sham (n = 16) or an IPOC (n = 16) intervention group. Biceps brachii muscle damage was induced by eccentric exercise, with IPOC or sham intervention applied on the dominant arm following exercise (3 cycles of 30 s ischaemia). Visual analogue scale (VAS) pain, arm circumference, muscle thickness, echo-intensity, and microvascular function (using near-infrared spectroscopy) were measured bilaterally at baseline, 24, 48, and 72 hours after eccentric exercise. Biceps curl one repetition maximum (1RM) was also measured. 1RM was higher for the IPOC group at 48 and 72 hours (both p < 0.05). On the dominant arm, VAS pain was lower at 72 hours for the IPOC group (p = 0.039). Muscle thickness was lower at all post-exercise time points for the IPOC group (all p < 0.05). VAS pain, echo-intensity, and arm circumference were elevated on the non-dominant arm in the sham group at 72 hours (all p < 0.05). These parameters all returned to the baseline level for the IPOC group at 72 hours (all p > 0.05IPOC could attenuate the decrease in strength, and alleviate EIMD with both local and remote effects after high-intensity exercise.

Impaired pre-competition wellbeing measures can negatively impact running performance in developmental youth female soccer players.

This study aimed to determine the association between pre-competition perceived player wellbeing measures and subsequent relative and peak running performance of developmental youth female soccer players (n = 15, age: 16 ± 1 years). Total distance (TD), high-speed (> 3.5 m/s) (HSRD) and very high-speed (> 5.3 m/s) running (VHSRD) were expressed using 1-, 2- and 5-minute epochs and relative (per minute) calculations. Fatigue, sleep quality, upper and lower-body muscle soreness, stress, and mood wellbeing measures were collected via a self-reported questionnaire (1-5 Likert scale). Menstrual cycle phase was collected via a calendar-based countback method. Results demonstrated that reductions in stress was associated with decreased relative and peak TD in all epochs (p = 0.008-0.040), relative and peak HSRD (p = 0.006-0.039) in 2- and 5-minute epochs as well as VHSRD in 2-minute epochs (p = 0.026). For example, a one-point reduction of 'normal' to 'relaxed' is associated with a decrease of 7 m/min in peak TD for 1-minute epochs. One-point increase in fatigue (e.g., 'normal' to 'more tired than normal') displayed a decrease of 7 m/min peak TD for 2-minute (p = 0.048) and 9 m/min for 5-minute (p = 0.007) rolling epochs. Likewise, one-point increase in lower-body muscle-soreness (e.g., 'normal' to 'increase in soreness/tightness') was associated with a reduction of 6 m/min peak VHSRD for 1-minute epochs (p = 0.034). Results suggest that perceived player wellbeing can influence running performance. However, the magnitude of the change in player wellbeing should be considered in a practical sense.

Effects of Percussive Massage Treatments on Symptoms Associated with Eccentric Exercise-Induced Muscle Damage.

Percussive massage (PM) is an emerging recovery treatment despite the lack of research on its effects post-eccentric exercise (post-EE). This study investigated the effects of PM treatments (immediately, 24, 48, and 72 h post-EE) on the maximal isometric torque (MIT), range of motion (ROM), and an 11-point numerical rating scale (NRS) of soreness of the nondominant arm's biceps brachii from 24-72 h post-EE. Seventeen untrained, college-aged subjects performed 60 eccentric elbow flexion actions with their nondominant arms. Nine received 1 minute of PM, versus eight who rested quietly (control [CON]). In order, NRS, ROM, and MIT (relative to body mass) were collected pre-eccentric exercise (pre-EE) and after treatment (AT) at 24, 48, and 72 h post-EE. NRS was also collected before treatment (BT). Electromyographic (EMG) and mechanomyographic (MMG) amplitudes were collected during the MIT and normalized to pre-EE. There were no interactions for MIT, EMG, or MMG, but there were interactions for ROM and NRS. For ROM, the PM group had higher values than the CON 24-72 h by ~6-8°, a faster return to pre-EE (PM: 48 h, CON: 72 h), and exceeded their pre-EE at 72 h by ~4°. The groups' NRS values did not differ BT 24-72 h; however, the PM group lowered their NRS from BT to AT within every visit by ~1 point per visit, which resulted in them having lower values than the CON from 24-72 h by ~2-3 points. Additionally, the PM group returned their NRS to pre-EE faster than the CON (PM: BT 72 h, CON: never). In conclusion, PM treatments may improve ROM without affecting isometric strength or muscle activation 24-72 h post-EE. Although the PM treatments did not enhance the recovery from delayed onset muscle soreness until 72 h, they consistently provided immediate, temporary relief when used 24-72 h post-EE.

Effects of Omega-3 Supplementation on the Delayed Onset Muscle Soreness after Cycling High Intensity Interval Training in Overweight or Obese Males.

People with overweight or obesity preferred high-intensity interval training (HIIT) due to the time-efficiency and pleasure. However, HIIT leads to delayed onset muscle soreness (DOMS). The present study aimed to investigate the effects of omega-3 supplementation on DOMS, muscle damage, and acute inflammatory markers induced by cycling HIIT in untrained males with overweight or obesity. A randomized, double-blinded study was used in the present study. Twenty-four males with a sedentary lifestyle were randomly assigned to either receive omega-3 (O3) (4 g fish oil) or placebo (Con). Subjects consumed the capsules for 4 weeks and performed cycling HIIT at the 4th week. After 4 weeks-intervention, the omega-3 index of O3 group increased by 52.51% compared to the baseline. All subjects performed HIIT at 4th week. The plasma creatine kinase (CK) level of Con group increased throughout 48h after HIIT. While the CK level of O3 group increased only immediately and 24h after HIIT and decreased at 48h after HIIT. The white blood cell count (WBC) of Con group increased immediately after the HIIT, while O3 group did not show such increase. There was no change of CRP in both groups. O3 group had a higher reduction of calf pain score compared to Con group. O3 group also showed a recovery of leg strength faster than Con group. Omega-3 supplementation for 4 weeks lower increased CK level, reduced calf pain score, and recovery leg strength, DOMS markers after cycling HIIT.

Sodium and quantitative hydrogen parameter changes in muscle tissue after eccentric exercise and in delayed-onset muscle soreness assessed with magnetic resonance imaging.

The objective of the current study was to assess sodium (23 Na) and quantitative proton (1 H) parameter changes in muscle tissue with magnetic resonance imaging (MRI) after eccentric exercise and in delayed-onset muscle soreness (DOMS). Fourteen participants (mean age: 25 ± 4 years) underwent 23 Na/1 H MRI of the calf muscle on a 3-T MRI system before exercise (t0), directly after eccentric exercise (t1), and 48 h postintervention (t2). In addition to tissue sodium concentration (TSC), intracellular-weighted sodium (ICwS) signal was acquired using a three-dimensional density-adapted radial projection readout with an additional inversion recovery preparation module. Phantoms containing saline solution served as references to quantify sodium concentrations. The 1 H MRI protocol consisted of a T1 -weighted turbo spin echo sequence, a T2 -weighted turbo inversion recovery, as well as water T2 mapping and water T1 mapping. Additionally, blood serum creatine kinase (CK) levels were assessed at baseline and 48 h after exercise. The TSC and ICwS of exercised muscles increased significantly from t0 to t1 and decreased significantly from t1 to t2. In the soleus muscle (SM), ICwS decreased below baseline values at t2. In the tibialis anterior muscle (TA), TSC and ICwS remained at baseline levels at each measurement point. However, high-CK participants (i.e., participants with a more than 10-fold CK increase, n = 3) displayed different behavior, with 2- to 4-fold increases in TSC values in the medial gastrocnemius muscle (MGM) at t2. 1 H water T1 relaxation times increased significantly after 48 h in the MGM and SM. 1 H water T2 relaxation times and muscle volume increased in the MGM at t2. Sodium MRI parameters and water relaxation times peaked at different points. Whereas water relaxation times were highest at t2, sodium MRI parameters had already returned to baseline values (or even below baseline values, for low-CK participants) by this point. The observed changes in ion concentrations and water relaxation time parameters could enable a better understanding of the physiological processes during DOMS and muscle regeneration. In the future, this might help to optimize training and to reduce associated sports injuries.

The effect of dietary anthocyanins on biochemical, physiological, and subjective exercise recovery: a systematic review and meta-analysis.

Anthocyanins (ACN), the sub-class of (poly)phenols responsible for the red-blue-purple pigmentation of fruit and vegetables, have gained considerable interest in sport and exercise research due to their potential to facilitate exercise recovery. A systematic literature search was performed using PubMed, The Cochrane Library, MEDLINE, SPORTDiscus and CINAHL. Thirty nine studies were included and the standardized mean difference (Hedges g) for creatine kinase (CK), anti-oxidative and inflammatory markers, strength, power and delayed onset muscle soreness (DOMS) indices were pooled in separate meta-analyses; meta-regression was also performed on reported ACN dose. Immediately post-exercise there was an increase in antioxidant capacity (g: 0.56) and reduced C reactive protein (g: -0.24) and tumor necrosis factor α (g: -40); p ≤ 0.02. Strength was improved with ACN at all time points (g: 0.45-0.67). DOMS (g: -0.23) was lower 24 hours post-exercise and power was improved 24 hours (g: 0.62) and 48 hours (g: 0.57) post exercise. The CK was lower 48 hours post-exercise (g: -0.31) and there was a trend for a positive association with ACN dose (p = 0.057). This systematic review provides new data showing ACN-rich foods promote functional and subjective recovery likely due to the antioxidant and anti-inflammatory properties of ACN.

Effects of Multi-joint Eccentric Training on Muscle Function When Combined With Aquatic Plyometric Training: A Minimal Dose, Mixed Training Study.

OBJECTIVES: To examine the effects of a combined eccentric overload and aquatic-based plyometric training program on muscle function/performance measures and soreness versus an eccentric-only training protocol using a minimal dose training paradigm. METHODS: Twenty-five participants were randomized into either an eccentric-only training group (ECC) or a combined eccentric and aquatic plyometric group (ECC + AQP). The ECC group performed eccentric training once per week for 6-weeks while the ECC + AQP group performed the same eccentric training but with an additional aquatic plyometric training session. RESULTS: There was no group × trial interactions for any of the variables. However, the training elicited large improvements in eccentric strength in both ECC (27%; ES = 1.33) and ECC+AQP (17%; ES = .86) groups. Isometric strength improved moderately for ECC and ECC+AQP groups (17.2%, ES = .53;9%, ES = .45). A moderate increase was observed for depth jump height for both ECC and ECC+AQP groups (13.1%, ES = .48;8.8%, ES = .36). No changes were observed for countermovement jump or sprint time and muscle soreness did not differ between groups. CONCLUSIONS: Minimal dose multi-joint eccentric overload training improved strength and depth jump outcomes after 6-weeks regardless of the training condition but adding a minimal dose aquatic plyometric protocol does not improve muscle function-based outcomes.

The dose-response of pain throughout a Nordic hamstring exercise intervention.

The Nordic hamstring exercise (NHE) reduces hamstring injury incidence. Compliance to large exercise volumes of the NHE is poor, with exercise related soreness often seen as a contributing factor. We investigated the dose-response of NHE exposure with delayed onset muscle soreness (DOMS) and non-DOMS pain. Forty males were randomized to a 6-week intervention of four different NHE dosages: Group 1: very low volume; Group 2: low volume; Group 3: initial high to low volume; Group 4: low to high volume. Group 4 experienced more DOMS (p < 0.05) and non-DOMS pain (p = 0.030) than other groups. High volumes of NHE increase DOMS and non-DOMS pain while lower volume protocols have lesser DOMS and non-DOMS pain responses.

Muscle damage induced by maximal eccentric exercise of the elbow flexors after 3-week immobilization.

The present study investigated the effects of a 3-week immobilization (IM) on muscle damage induced by maximal eccentric exercise (MaxEC) to test the hypothesis that the IM would make muscles prone to muscle damage. Young healthy sedentary men were pseudo-randomly assigned to IM or control group (n = 12/group). Non-dominant arms of the IM group participants were immobilized at 90° elbow flexion by a cast for 21 days. All participants performed MaxEC consisting of five sets of six elbow flexor contractions by lowering a dumbbell set at 100% of pre-exercise maximal voluntary isometric contraction (MVC) strength of the non-dominant arm. This was performed at 2 days after the cast removal for the IM group. MVC torque, range of motion (ROM), muscle thickness (MT), muscle hardness, position sense (PS), and joint reaction angle (JRA) of the elbow flexors were measured at baseline, post-immobilization, and before, immediately after, and one to 5 days after MaxEC. The IM decreased MVC torque (-17 ± 2%), ROM (-2 ± 1%), MT (-7 ± 3%), and JRA (-12 ± 6%), and increased in muscle hardness (20 ± 6%) and PS (11 ± 2%) (p < 0.05). Changes in MVC (e.g., 2 days: -40 ± 5 vs. -30 ± 9%), ROM (2 days: -11 ± 2 vs. -9 ± 3%), muscle soreness (peak: 63 ± 22 vs. 48 ± 14 mm), plasma CK activity (peak: 7820 ± 4011 vs. 4980 ± 1363 IU/L), PS (maximal change: -23 ± 2 vs. -18 ± 3%), and JRA (maximal change: -37 ± 4 vs. -26 ± 3%) after MaxEC were greater (p < 0.05) for the IM than control group. These results supported the hypothesis and showed that the IM made the muscles more vulnerable to muscle damage induced by eccentric exercise.

Contralateral versus ipsilateral protective effect against muscle damage of the elbow flexors and knee extensors induced by maximal eccentric exercise.

The present study compared the ipsilateral repeated bout effect (IL-RBE) and contralateral repeated bout effect (CL-RBE) of the elbow flexors (EF) and knee flexors (KF) for the same interval between bouts to shed light on their mechanisms. Fifty-two healthy sedentary young (20-28 years) men were randomly assigned to the IL-EF, IL-KF, CL-EF, and CL-KF groups (n = 13/group). Thirty maximal eccentric contractions of the EF were performed in IL-EF and CL-EF, and 60 maximal eccentric contractions of the KF were performed in IL-KF and CL-KF, with a 2-week interval between bouts. Changes in muscle damage markers such as maximal voluntary contraction (MVC) torque, muscle soreness, and plasma creatine kinase activity, and proprioception measures before to 5 days post-exercise were compared between groups. Changes in all variables were greater (p < 0.05) after the first than second bout for all groups, and the changes were greater (p < 0.05) for the EF than KF. The changes in all variables after the second bout were greater (p < 0.05) for the CL than IL condition for both EF and KF. The magnitude of the average protective effect was similar between CL-EF (33%) and CL-KF (32%), but slightly greater (p < 0.05) for IL-EF (67%) than IL-KF (61%). These demonstrate that the magnitude of CL-RBE relative to IL-RBE was similar between the EF and KF (approximately 50%), regardless of the greater muscle damage for the EF than KF. It appears that the CL-RBE is more associated with neural adaptations at cerebrum, cerebellum, interhemispheric inhibition, and coricospinal tract, but the IL-RBE is induced by additional adaptations at muscles.

The acute and repeated bout effects of multi-joint eccentric exercise on physical function and balance in older adults.

PURPOSE: Eccentric muscle actions generate high levels of force at a low metabolic cost, making them a suitable training modality to combat age-related neuromuscular decline. The temporary muscle soreness associated with high intensity eccentric contractions may explain their limited use in clinical exercise prescription, however any discomfort is often alleviated after the initial bout (repeated bout effect). Therefore, the aims of the present study were to examine the acute and repeated bout effects of eccentric contractions on neuromuscular factors associated with the risk of falling in older adults. METHODS: Balance, functional ability [timed up-and-go and sit-to-stand], and lower-limb maximal and explosive strength were measured in 13 participants (67.6 ± 4.9 year) pre- and post-eccentric exercise (0, 24, 48, and 72 hr) in Bout 1 and 14 days later in Bout 2. The eccentric exercise intervention was performed on an isokinetic unilateral stepper ergometer at 50% of maximal eccentric strength at 18 step‧min-1 per limb for 7 min (126 steps per limb). Two-way repeated measures ANOVAs were conducted to identify any significant effects (P ≤ 0.05). RESULTS: Eccentric strength significantly decreased (- 13%) in Bout 1 at 24 hr post-exercise; no significant reduction was observed at any other time-point after Bout 1. No significant reductions occurred in static balance or functional ability at any time-point in either bout. CONCLUSION: Submaximal multi-joint eccentric exercise results in minimal disruption to neuromuscular function associated with falls in older adults after the initial bout.

Evaluation of a preemptive intervention regimen with hesperidin methyl chalcone in delayed-onset muscle soreness in young adults: a randomized, double-blinded, and placebo-controlled trial study.

PURPOSE: Delayed-onset muscle soreness (DOMS) describes an entity characterized by ultrastructural muscle damage. Hesperidin methyl chalcone (HMC) is a synthetic flavonoid presenting analgesic, anti-inflammatory, and antioxidant properties. We evaluated the effects of HMC upon DOMS. METHOD: In a preventive paradigm, 31 sedentary young men were submitted to a randomized, double-blinded parallel trial and received HMC 500 mg or one placebo capsule × 3 days before an intense dynamic exercise protocol (concentric/eccentric actions) applied for lower limbs for inducing muscle damage. Assessments were conducted at baseline, and 24 and 48 h after, comprising physical performance, and post-muscle soreness and damage, inflammation, recovery of muscle strength, and postural balance associated with DOMS. HMC safety was also evaluated. Thirty participants completed the study. RESULTS: HMC improved the performance of participants during exercise (40.3 vs 51.3 repetitions to failure, p = 0.0187) and inhibited CPK levels (90.5 vs 57.9 U/L, p = 0.0391) and muscle soreness during passive quadriceps palpation (2.6 vs 1.4 VAS cm, p = 0.0439), but not during active actions, nor did it inhibit IL-1ß or IL-10 levels. HMC improved muscle strength recovery, and satisfactorily refined postural balance, without inducing injury to kidneys or liver. CONCLUSIONS: Preemptive HMC supplementation may be beneficial for boosting physical performance and for the amelioration of clinical parameters related to DOMS, including pain on muscle palpation, increased blood CPK levels, and muscle strength and proprioceptive deficits, without causing adverse effects. These data advance the understanding of the benefits provided by HMC for DOMS treatment, which supports its usefulness for such purpose.

Neuromuscular fatigue and muscle damage following a simulated singles badminton match.

PURPOSE: To understand muscle damage in badminton, changes in neuromuscular function were investigated after simulated badminton singles matches performed by ten state-level male players. METHODS: Each participant played eight matches and measurements were taken before, immediately after, and 1 and 24 h after each match. Maximal voluntary isometric contraction (MVC) torque of the knee extensors and flexors, voluntary activation (VA) during MVC and torques generated by doublet (TDoublet), 20 (T20) and 80 Hz (T80) electrical stimulations of the knee extensors were measured from the dominant leg (the racket-hold arm side). Muscle soreness was assessed by a 100-mm visual analogue scale from both legs. The number of lunges performed by each participant in each match was analysed by videos, and its relations to other measures were examined. RESULTS: Pre-match knee extensor and flexor MVC torques were 278.4 ± 50.8 Nm and 143.0 ± 36.2 Nm, respectively. Knee extensor MVC torque of the dominant leg decreased immediately (12.0 ± 2.9%) and 1 h post-match (16.0 ± 3.2%), but returned to baseline at 24 h post-match. VA (11.4 ± 2.9%), TDoublet (13.1 ± 6.0%), T20 (31.1 ± 12.3%) and T80 (25.5 ± 7.9%) decreased (p < 0.01) immediately post-match but recovered by 24 h post-match. A significant correlation (r = - 0.64, p < 0.01) was observed between the total number of lunges performed in a match (160-240 times) and the magnitude of decrease in MVC torque (6.4-14.7%). Muscle soreness developed more (p < 0.05) for the dominant (51.5 ± 11.6 mm) than the non-dominant leg (18.8 ± 8.6 mm). CONCLUSION: Muscle damage induced by singles badminton matches was minimal, but the more the lunges are performed, the greater the neuromuscular fatigue.

Eccentric exercise 24 h prior to hypobaric decompression increases decompression strain.

PURPOSE: Animal studies have shown that recent musculoskeletal injuries increase the risk of decompression sickness (DCS). However, to date no similar experimental study has been performed in humans. The aim was to investigate if exercise-induced muscle damage (EIMD)-as provoked by eccentric work and characterized by reduced strength and delayed-onset muscle soreness (DOMS)-leads to increased formation of venous gas emboli (VGE) during subsequent hypobaric exposure. METHODS: Each subject (n = 13) was on two occasions exposed to a simulated altitude of 24,000 ft for 90 min, whilst breathing oxygen. Twenty-four hours prior to one of the altitude exposures, each subject performed 15 min of eccentric arm-crank exercise. Markers of EIMD were reduction in isometric m. biceps brachii strength and DOMS as assessed on the Borg CR10 pain scale. The presence of VGE was measured in the right cardiac ventricle using ultrasound, with measurements performed at rest and after three leg kicks and three arm flexions. The degree of VGE was evaluated using the six-graded Eftedal-Brubakk scale and the Kisman integrated severity score (KISS). RESULTS: Eccentric exercise induced DOMS (median 6.5), reduced the biceps brachii strength (from 230 ± 62 N to 151 ± 8.8 N) and increased the mean KISS at 24,000 ft, both at rest (from 1.2 ± 2.3 to 6.9 ± 9.2, p = 0.01) and after arm flexions (from 3.8 ± 6.2 to 15.5 ± 17.3, p = 0.029). CONCLUSION: EIMD, induced by eccentric work, provokes release of VGE in response to acute decompression.

Physiological effects of microcurrent and its application for maximising acute responses and chronic adaptations to exercise.

Microcurrent is a non-invasive and safe electrotherapy applied through a series of sub-sensory electrical currents (less than 1 mA), which are of a similar magnitude to the currents generated endogenously by the human body. This review focuses on examining the physiological mechanisms mediating the effects of microcurrent when combined with different exercise modalities (e.g. endurance and strength) in healthy physically active individuals. The reviewed literature suggests the following candidate mechanisms could be involved in enhancing the effects of exercise when combined with microcurrent: (i) increased adenosine triphosphate resynthesis, (ii) maintenance of intercellular calcium homeostasis that in turn optimises exercise-induced structural and morphological adaptations, (iii) eliciting a hormone-like effect, which increases catecholamine secretion that in turn enhances exercise-induced lipolysis and (iv) enhanced muscle protein synthesis. In healthy individuals, despite a lack of standardisation on how microcurrent is combined with exercise (e.g. whether the microcurrent is pulsed or continuous), there is evidence concerning its effects in promoting body fat reduction, skeletal muscle remodelling and growth as well as attenuating delayed-onset muscle soreness. The greatest hindrance to understanding the combined effects of microcurrent and exercise is the variability of the implemented protocols, which adds further challenges to identifying the mechanisms, optimal patterns of current(s) and methodology of application. Future studies should standardise microcurrent protocols by accurately describing the used current [e.g. intensity (µA), frequency (Hz), application time (minutes) and treatment duration (e.g. weeks)] for specific exercise outcomes, e.g. strength and power, endurance, and gaining muscle mass or reducing body fat.