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.

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.

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.

Neurochemical mechanism of muscular pain: Insight from the study on delayed onset muscle soreness

We reviewed fundamental studies on muscular pain, encompassing the characteristics of primary afferent fibers and neurons, spinal and thalamic projections, several muscular pain models, and possible neurochemical mechanisms of muscle pain. Most parts of this review were based on data obtained from animal experiments, and some researches on humans were also introduced. We focused on delayed-onset muscle soreness (DOMS) induced by lengthening contractions (LC), suitable for studying myofascial pain syndromes. The muscular mechanical withdrawal threshold (MMWT) decreased 1-3 days after LC in rats. Changing the speed and range of stretching showed that muscle injury seldom occurred, except in extreme conditions, and that DOMS occurred in parameters without muscle damage. The B2 bradykinin receptor-nerve growth factor (NGF) route and COX-2-glial cell line-derived neurotrophic factor (GDNF) route were involved in the development of DOMS. The interactions between these routes occurred at two levels. A repeated-bout effect was observed in MMWT and NGF upregulation, and this study showed that adaptation possibly occurred before B2 bradykinin receptor activation. We have also briefly discussed the prevention and treatment of DOMS.

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.

Plasma α-Actin as an Early Marker of Muscle Damage After Repeated Bouts of Eccentric Cycling

Purpose: This study aimed to examine the changes in skeletal muscle (SM) α-actin, myoglobin (Mb) and hydroxyproline (HP) in plasma and other indirect markers of muscle damage after repeated bouts of eccentric cycling. Methods: Ten healthy men (23.3 ± 2.8 years) performed two 30-min eccentric cycling bouts at 100% of maximal concentric power output (230.7 ± 36.9 W) separated by 2 weeks (ECC1 and ECC2). Maximal voluntary isometric contraction (MVIC) peak force of the knee extensor muscles, muscle soreness (SOR), pain pressure threshold (PPT) and plasma levels of SM α-actin, Mb, and HP were measured before, 0.5, 3, 24-168 h after each cycling bout. Results: MVIC peak force decreased on average 10.7 ± 13.1% more after ECC1 than ECC2. SOR was 80% greater and PPT was 12-14% lower after ECC1 than ECC2. Plasma SM α-actin levels increased at 0.5, 3, and 24-72 h after ECC1 (26.1-47.9%), and SM α-actin levels at 24 h after ECC1 were associated with muscle strength loss (r = -0.56, P = .04) and SOR (r = 0.88, P = .001). Mb levels increased at 0.5, 3, and 24 h after ECC1 (200-502%). However, Mb levels at 24 h after ECC1were not associated with muscle strength loss and SOR. HP levels remained unchanged after ECC1. ECC2 did not increase SM α-actin, Mb and HP levels. Conclusion: Our results indicate that α-actin could be used as a potential marker for the early identification of SM damage due to its early appearance in plasma and its association with other indirect markers of muscle damage.

The Impact of Vocal Task on Voice Acoustics, Effort and Discomfort Following Submandibular Neuromuscular Electrical Stimulation in Healthy Adults

BACKGROUND

Neuromuscular electrical stimulation (NMES) offers a potential adjuvant to traditional voice therapy for individuals with dysphonia. The type of vocal task to implement in conjunction with electrical stimulation to achieve maximal therapeutic benefit is unknown. The purpose of this study was to elucidate the impact of tasks on voice outcomes.

METHODS

Nineteen vocally-healthy adult females, between 23 and 27 years of age (Ave: 23.8, SD: 1.13), participated in the study. 15 participants completed all three 30-minute sessions, and four completed at least one session. NMES was paired with three different voice conditions: high-pitched hum, low-pitched hum, and comfortable-pitched hum. Acoustic (average fundamental frequency and loudness; perturbation (jitter, shimmer, noise to harmonic ratio); Cepstral Spectral Index of Dysphonia; pitch range), perceived phonatory effort, and discomfort (delayed onset muscle soreness) measures were compared across conditions.

RESULTS

Eight participants experienced discomfort following NMES. Three participants withdrew from the study due to discomfort, and one withdrew due to an unrelated oral surgery. NMES paired with high-pitch humming resulted in increased average fundamental frequency during sustained phonation and reading tasks, and increased Cepstral Spectral Index of Dysphonia during sustained phonation. Low-pitch humming resulted in a decreased noise to harmonic ratio. No statistically significant changes in perceived phonatory effort were noted.

CONCLUSION

Almost half of the participants reported temporary discomfort. Task-specific differences in some outcomes were noted indicating that the nature of voice task performed with NMES must be considered when examining the impact of NMES on voice. Vocal tasks can impact discomfort and acoustic vocal outcomes of NMES.

Recovery from Resistance Exercise in Older Adults: A Systematic Scoping Review

BACKGROUND

Resistance exercise is recommended for maintaining muscle mass and strength in older adults. However, little is known about exercise-induced muscle damage and recovery from resistance exercise in older adults. This may have implications for exercise prescription. This scoping review aimed to identify and provide a broad overview of the available literature, examine how this research has been conducted, and identify current knowledge gaps relating to exercise-induced muscle damage and recovery from resistance exercise in older adults.

METHODS

Studies were included if they included older adults aged 65 years and over, and reported any markers of exercise-induced muscle damage after performing a bout of resistance exercise. The following electronic databases were searched using a combination of MeSH terms and free text: MEDLINE, Scopus, Embase, SPORTDiscus and Web of Science. Additionally, reference lists of identified articles were screened for eligible studies. Data were extracted from eligible studies using a standardised form. Studies were collated and are reported by emergent theme or outcomes.

RESULTS

A total of 10,976 possible articles were identified and 27 original research articles were included. Findings are reported by theme; sex differences in recovery from resistance exercise, symptoms of exercise-induced muscle damage, and biological markers of muscle damage.

CONCLUSIONS

Despite the volume of available data, there is considerable variability in study protocols and inconsistency in findings reported. Across all measures of exercise-induced muscle damage, data in women are lacking when compared to males, and rectifying this discrepancy should be a focus of future studies. Current available data make it challenging to provide clear recommendations to those prescribing resistance exercise for older people.

Whole-body vibration decreases delayed onset muscle soreness following eccentric exercise in elite hockey players: a randomised controlled trial

BACKGROUND

Delayed onset muscle soreness (DOMS) is a common non-structural muscle injury which can disrupt training and impair performance in elite athletes. Vibration therapy reduces inflammation and improves neuromuscular efficiency, leading to reductions in pain and stiffness, and may be effective for the prevention or treatment of DOMS. However, the effect of whole-body vibration (WBV) used after sport in elite athletes has not been reported.

METHODS

A randomised, controlled trial was performed. Participants were elite (national or international level) hockey players and underwent an eccentric exercise protocol previously shown to produce clinical DOMS. After exercise, one group underwent static stretching with WBV therapy, and the other performed stretching only. Baseline and serial post-exercise pain scores and measurements of quadriceps tightness were obtained.

RESULTS

Eleven participants were recruited into each study arm. There were no significant differences in baseline group characteristics. Participants receiving WBV had significant reductions in both pain (p = 0.04) and quadriceps tightness (p = 0.02) compared with stretching only.

CONCLUSIONS

Post-exercise WBV is effective in elite hockey players to reduce DOMS after eccentric exercise. Elite athletes in multi-sprint sports are at risk of DOMS during training and competition, and its reduction could contribute to reduced injury risk and improved performance. This treatment modality is favourable because it can be incorporated with minimal disruption into the recovery section of existing training regimes. These findings may also be extrapolated to other multi-sprint sports.

Neuromuscular responses to isometric, concentric and eccentric contractions of the knee extensors at the same torque-time integral

PURPOSE

The present study compared isometric, concentric and eccentric contractions at the same torque-time integral for changes in neuromuscular fatigue and muscle damage parameters.

METHOD

Healthy men (18-24 years) were placed to either isometric (ISO), concentric (CONC), or eccentric (ECC) group (n = 11/group) that performed corresponding contractions of the knee extensors to exert the same amount of torque-time integral (24,427 ± 291 Nm·s). Changes in maximal voluntary contraction (MVC) torque, voluntary activation, evoked torque at 10 Hz and 100 Hz and its ratio, M-wave amplitude, and muscle soreness were assessed immediately before and after, 1 h, 1 day and 2 days after each exercise, and were compared among the groups.

RESULTS

MVC torque decreased immediately after ISO (- 17.0 ± 8.3%), CONC (- 21.7 ± 11.5%) and ECC (- 26.2 ± 15.6%) similarly (p = 0.35), but the decrease sustained longer (p < 0.05) for ECC (2 days post-exercise: - 12.9 ± 14.8%) and ISO (- 5.5 ± 7.9%) than CONC (+ 5.0 ± 11.0%). Muscle soreness developed after ECC (25.1 ± 19.8 mm) and ISO (17.5 ± 21.0 mm) similarly (p = 0.15). Voluntary activation decreased immediately (- 3.7 ± 6.6%) and 1 h post-exercise (- 4.7 ± 7.6%) for all groups similarly. Electrically evoked forces decreased greater immediately (- 30.1 ± 15.6%) and 1 h post-exercise (- 35.0 ± 12.8%) for ECC than others, and the decrease in 10/100 Hz ratio was also greater immediately (- 30.5 ± 12.6%) and 1 h after ECC (- 23.8 ± 10.3%) than others.

CONCLUSION

ISO, CONC and ECC with the same torque-time integral produced similar neuromuscular fatigue at immediately post-exercise, but the force loss was longer-lasting after ISO and ECC than CONC, and the changes in peripheral fatigue parameters were the greatest after ECC, suggesting greater muscle damage.

Associations of Regional and Network Functional Connectivity With Exercise-Induced Low Back Pain

Musculoskeletal pain is an aversive experience that exists within a variety of conditions and can result in significant impairment for individuals. Gaining greater understanding of the factors related to pain vulnerability and resilience to musculoskeletal pain may help target at-risk individuals for early intervention. This analysis builds on our previous work identifying regions where greater gray matter density was associated with lower pain following standardized, exercise induced musculoskeletal injury. Here we sought to examine the relationship between baseline resting state functional connectivity in a priori regions and networks, and delayed onset muscle soreness (DOMS) pain intensity following a single session of eccentric exercise in healthy adults. Participants completed a baseline functional MRI scan and a high intensity trunk exercise protocol in the erector spinae. Pain intensity ratings were collected 48-hours later. Resting state functional connectivity from four seed regions and 3 networks were separately regressed on pain intensity scores. Results revealed that connectivity between left middle frontal gyrus, the left occipital gyrus and cerebellar network seeds and clusters associated with discriminative, emotional, and cognitive aspects of pain were associated with lower post-DOMS pain. Results suggest resilience to clinically relevant pain is associated with aspects of regional and network neural coherence. Investigations of pain modulatory capacity that integrate multimodal neuroimaging metrics are called for. Perspective: Our results provide key support for the role of structural and functional coherence in regional and network connectivity in adaptive pain response and represent an important step in clarifying neural mechanisms of resilience to clinically relevant pain.

Training endogenous pain modulation: a preliminary investigation of neural adaptation following repeated exposure to clinically-relevant pain

Analgesic treatments that aim to eliminate pain display marginal success in relieving chronic pain and may increase pain vulnerability. Repeated exposure to pain may result in increased pain modulation via engagement of anti-nociceptive brain regions. It was hypothesized that repeated exposure to delayed onset muscle soreness (DOMS) would result in increased pain modulatory capacity (PMC) via functional neural adaptation. 23 healthy participants completed Baseline and Follow Up resting-state fMRI and quantitative sensory testing (QST) visits 40 days apart. Participants were randomized to two groups: A Repeated DOMS Group (RD Group) that received four, weekly DOMS inductions and a Control Group that received one baseline induction. Daily pain ratings were collected for seven days post-induction, as were quantitative sensory testing (QST) metrics at baseline and Follow Up. Regional functional connectivity (FC) was estimated among areas involved in pain modulation. Seed and network FC was estimated among areas involved in pain modulation and sensory processing. Changes in FC were compared between groups. The RD Group displayed significant reductions in post-DOMS pain ratings and significant changes in thermal QST measures. RD Group participants displayed greater adaptation in nucleus accumbens-medial prefrontal cortex (NAc-mPFC) FC and in sensorimotor network (SMN) connectivity with the dorsomedial, ventromedial, and rostromedial prefrontal cortices. Changes in SMN-PFC connectivity correlated with reductions in post-DOMS affective distress. Results suggest that repeated exposure to clinically-relevant pain results in adaptations among brain regions involved in pain modulation. Repeated exposure to clinically-relevant pain may serve as a mechanism to increase PMC via inhibition of emotional valuation of painful stimuli.

The effect of acute and repeated ischemic preconditioning on recovery following exercise-induced muscle damage

OBJECTIVES

The aim of this investigation was to determine if acute or repeated applications of ischemic preconditioning (IPC) could enhance the recovery process, following exercise induced muscle damage (EIMD).

DESIGN

Randomized control trial.

METHODS

Twenty-three healthy males were familiarised with the muscle damaging protocol (five sets of 20 drop jumps from a 0.6 m box) and randomly allocated to one of three groups: SHAM (3 × 5 min at 20 mmHg), Acute IPC (3 × 5 min at 220 mmHg) and Repeated IPC (3 days x 3 × 5 min at 220 mmHg). The indices of muscle damage measured included creatine kinase concentration ([CK]), thigh swelling, delayed onset muscle soreness, counter movement jumps (CMJ) and maximal voluntary isometric contraction (MVIC).

RESULTS

Both acute and repeated IPC improved recovery in MVIC versus SHAM. Repeated IPC led to a faster MVIC recovery at 48 h (101.5%) relative to acute IPC (92.6%) and SHAM (84.4%) (P <  0.05). Less swelling was found for both acute and repeated IPC vs. SHAM (P <  0.05) but no group effects were found for CMJ, soreness or [CK] responses (P >  0.05).

CONCLUSION

Taken together, repeated IPC can enhance recovery time of MVIC more than an acute application, and both reduce swelling following EIMD, relative to a SHAM condition.

Does delayed onset muscle soreness affect the biomechanical variables of the drop vertical jump that have been associated with increased ACL injury risk? A randomised control trial

INTRODUCTION

Delayed onset muscle soreness (DOMS) and Anterior Cruciate Ligament (ACL) injuries are both prevalent in sport. It is currently unknown whether DOMS increases ACL injury risk.

AIM

This study aimed to provide preliminary insight on whether DOMS affects ACL injury risk by investigating whether DOMS affects the biomechanical variables of the DVJ that have been identified as risk factors for future ACL injury.

METHODS

This was a randomised control trial involving 32 active individuals aged 18-35 years, with no history of ACL injury. Participants underwent two sessions of force-plate testing and 3D motion analysis of the drop vertical jump (DVJ). The DVJ was chosen as it has been investigated prospectively for association with future ACL injury. Initial testing was followed by randomisation to DOMS or control group. The DOMS group underwent a DOMS-inducing exercise protocol, the control group did not. Both groups were re-tested 48 h after initial testing. Five variables of the DVJ that have been associated with future ACL injury were chosen for analysis - peak knee flexion angle, peak vertical ground reaction force, ground contact time, peak knee abduction angle & peak knee abduction moment. Between-group differences were compared using a two-way mixed analysis of variance; alpha level set to 0.05.

RESULTS

DOMS was successfully induced in all participants of the DOMS group however no statistically significant group x time interactions were found for any of the five variables analysed.

CONCLUSIONS

DOMS did not affect the biomechanical variables of the DVJ that have been associated with future ACL injury. By extension, this may suggest that DOMS might not affect ACL injury risk. However, it is also possible that certain attributes of the DVJ meant that any effect of DOMS was simply unable to be quantified, even if an effect existed. All considered, our position is that conclusion cannot be drawn from this study alone on whether DOMS affects ACL injury risk. Further research is required.

Sex moderates the effects of experimentally induced musculoskeletal pain on alcohol demand in healthy drinkers

BACKGROUND

Pain may serve as an antecedent for alcohol use, increasing risk for hazardous drinking and associated consequences. Delayed onset muscle soreness (DOMS) induction produces clinically relevant but time-limited musculoskeletal pain. This study was conducted to determine whether DOMS induction on the dominant elbow flexors influenced alcohol demand using the Alcohol Purchase Task (APT). We hypothesized DOMS would increase alcohol demand relative to a sham control. Based on existing studies of pain self-medication, we expected DOMS-related increases in alcohol demand would be greatest in men.

METHODS

Participants (N = 53; 57 % women) were randomly assigned to a DOMS (eccentric exercise) or sham condition (concentric exercise). Participants completed the APT pre-exercise and 48 -hs post-exercise. Repeated measures GLM was used to characterize group by sex by time interactions on APT indices, including intensity, breakpoint, essential value (EV), O_max, and P_max.

RESULTS

The DOMS procedure significantly increased pain ratings at the elbow flexors. Men had significantly higher demand intensity than women across groups and time points. Significant interactive effects were detected for breakpoint and EV. From pre- to post-test, breakpoint significantly increased in men in the DOMS group. However, breakpoint and EV significantly decreased in women in the DOMS group.

CONCLUSIONS

Increased alcohol demand in men in the DOMS group was consistent with epidemiological data suggesting men are at higher risk for self-medicating pain with alcohol than women. However, decreased demand in women was unexpected. Taken together, results indicate DOMS induction may be a useful means to characterize pain as an antecedent for alcohol use.

Heat and cold therapy reduce pain in patients with delayed onset muscle soreness: A systematic review and meta-analysis of 32 randomized controlled trials

OBJECTIVE

The aim of this review and meta-analysis was to evaluate the effect of heat and cold therapy on the treatment of delayed onset muscle soreness (DOMS).

METHODS

We followed our protocol that was registered in PROSPERO with ID CRD42020170632. A systematic review and meta-analysis of randomized controlled trials (RCT) was conducted. Nine databases were searched up to December 2020. Data was extracted from the retained studies and underwent methodological quality assessment and meta-analysis.

RESULTS

A total of 32 RCTs involving 1098 patients were included. Meta-analysis showed that, the application of cold therapy within 1 h after exercise could reduce the pain of DOMS patients within 24 h (≤24 h) after exercise (SMD -0.57,95%CI -0.89 to -0.25, P = 0.0005) and had no obvious effect within more than 24 h (>24 h) (P = 0.05). In cold therapies, cold water immersion (SMD -0.48, 95%CI -0.84 to -0.13, P = 0.008) and other cold therapies (SMD -0.68, 95%CI -1.28 to -0.08, P = 0.03) had the significant effects within 24 h. Heat treatment could reduce the pain of patients. It had obvious effects on the pain within 24 h (SMD -1.17, 95%CI -2.62 to -0.09, P = 0.03) and over 24 h (SMD -0.82, 95%CI -1.38 to -0.26, P = 0.004). Hot pack effect was the most obvious, which reduced the pain within 24 h (SMD -2.31, 95%CI -4.33 to -0.29, P = 0.03) and over 24 h (SMD -1.78, 95%CI -2.97 to -0.59, P = 0.003). Other thermal therapies were not statistically significant (P > 0.05). Both cold and heat showed effect in reducing pain of patients, however there was no significant difference between cold and heat group (P = 0.16).

CONCLUSIONS

The current evidence indicated that the application of cold and heat therapy within 1 h after exercise could effectively reduce the pain degree of DOMS patients for 24 h cold water immersion and hot pack therapy, which had the best effect, could promote the recovery of DOMS patients. But more high-quality studies are needed to confirm whether cold or heat therapy work better.

Changes in plasma hydroxyproline and plasma cell-free DNA concentrations after higher- versus lower-intensity eccentric cycling

PURPOSE

We examined changes in plasma creatine kinase (CK) activity, hydroxyproline and cell-free DNA (cfDNA) concentrations in relation to changes in maximum voluntary isometric contraction (MVIC) torque and delayed-onset muscle soreness (DOMS) following a session of volume-matched higher- (HI) versus lower-intensity (LI) eccentric cycling exercise.

METHODS

Healthy young men performed either 5 × 1-min HI at 20% of peak power output (n = 11) or 5 × 4-min LI eccentric cycling at 5% of peak power output (n = 9). Changes in knee extensor MVIC torque, DOMS, plasma CK activity, and hydroxyproline and cfDNA concentrations before, immediately after, and 24-72 h post-exercise were compared between groups.

RESULTS

Plasma CK activity increased post-exercise (141 ± 73.5%) and MVIC torque decreased from immediately (13.3 ± 7.8%) to 48 h (6.7 ± 13.5%) post-exercise (P < 0.05), without significant differences between groups. DOMS was greater after HI (peak: 4.5 ± 3.0 on a 10-point scale) than LI (1.2 ± 1.0). Hydroxyproline concentration increased 40-53% at 24-72 h after both LI and HI (P < 0.05). cfDNA concentration increased immediately after HI only (2.3 ± 0.9-fold, P < 0.001), with a significant difference between groups (P = 0.002). Lack of detectable methylated HOXD4 indicated that the cfDNA was not derived from skeletal muscle. No significant correlations were evident between the magnitude of change in the measures, but the cfDNA increase immediately post-exercise was correlated with the maximal change in heart rate during exercise (r = 0.513, P = 0.025).

CONCLUSION

Changes in plasma hydroxyproline and cfDNA concentrations were not associated with muscle fiber damage, but the increased hydroxyproline in both groups suggests increased collagen turnover. cfDNA may be a useful metabolic-intensity exercise marker.

The effectiveness of low intensity exercise and blood flow restriction without exercise on exercise induced muscle damage: A systematic review

OBJECTIVE

To investigate the evidence and provide clinical recommendations for low intensity exercises(LIE) and blood flow restriction(BFR) without exercise on reducing the effects of exercise induced muscle damage(EIMD).

METHOD

PubMed, Embase, Web of science, and PEDro(Physiotherapy Evidence Database) were searched up to December 2019 for studies that included LIE or BFR without exercise and their effect on EIMD.

RESULTS

Out of 3192 studies, 23 were included with 17 on LIE and 6 on BFR without exercise. 11 studies demonstrated positive effects for LIE on EIMD, with two level 2 and nine level 3 studies. Two level 2 and two level 3 studies found benefits for BFR without exercise on reducing the negative effects of EIMD, while two level 2 studies found did not find benefits for BFR without exercise.

CONCLUSION

Moderate to low levels of evidence supported LIE, particularly in the form of protective low load eccentric exercise, in reducing the negative effects of EIMD. Conflicting moderate to low levels of evidence was found regarding BFR without exercise. There does seem to be potential benefit for BFR without exercise in untrained individuals. Clinicians can provide clinical recommendations as LIE and BFR without exercise reducing EIMD.

Correlating clinical assessment and MRI findings in diagnosing calf injuries in elite male Australian rules footballers

OBJECTIVE

Calf complex injuries represent a significant injury burden among Australian Rules athletes. To date, there has been limited research correlating clinical and radiological findings of pathology within the calf. The objective of this study is to determine how accurately magnetic resonance imaging (MRI) findings correlate with clinical measures of calf muscle complex pathology in elite male athletes.

MATERIALS AND METHODS

A prospective cohort study was conducted on Australian rules elite athletes. A cohort of 45 athletes underwent a high-load training session of approximately 10 km of running. Athletes were then assessed by a sports physiotherapist who made a diagnosis of no pathology, delayed onset muscle soreness, strain or other. Subsequently, the athletes underwent MRI of their bilateral calf complexes. Radiologists interpreted the MRI findings and radiological diagnosis were correlated with clinical diagnosis.

RESULTS

A total of 90 calf MRIs were performed. Correlation of clinical and radiological diagnosis occurred in 57 cases. Of the 33 cases which did not correlate, there were 4 radiologically significant acute calf strains in clinically asymptomatic athletes, 3 of which involved old scar tissue.

CONCLUSION

MRI may detect clinically insignificant injuries within the calf complex. If an athlete does not have any clinically relevant symptoms, abnormal signal on MRI may represent a different diagnosis to muscle strain. Signal change on MRI proximal to scar tissue may represent reactive oedema. Clinical history and examination should be correlated with radiological findings is recommended when diagnosing calf injury in elite athletes.

Prolonged cooling with phase change material enhances recovery and does not affect the subsequent repeated bout effect following exercise

PURPOSE

The aim of this investigation was twofold: (1) to examine the effect of prolonged phase change material (PCM) cooling following eccentric exercise of the quadriceps on indices of muscle damage, and (2) to elucidate whether application of PCM cooling blunted the acute adaptive response to eccentric exercise, known as the repeated bout effect (RBE).

METHODS

Twenty-six males (25 ± 6 years) performed an initial bout (B1) of 120 eccentric quadriceps contractions on each leg at 90% of their isometric strength and were then randomized to receive PCM packs frozen at 15 °C (treatment) or melted packs (control) worn directly on the skin under shorts for 6 h. The protocol was repeated 14 days later (B2) with all participants receiving the control condition.

RESULTS

PCM cooling provided protection against strength loss in B1 (P = 0.005) with no difference in strength between treatment groups in B2 (P = 0.172; bout by treatment by time P = 0.008). PCM cooling reduced soreness in B1 (P = 0.009) with no difference between treatment groups in B2 (P = 0.061). Soreness was overall lower following B2 than B1 (P < 0.001). CK was elevated in B1 (P < 0.0001) and reduced in B2 (P < 0.001) with no difference between treatments. The damage protocol did not elevate hsCRP in B1, with no difference between treatments or between bouts.

CONCLUSIONS

This work provides further evidence that PCM cooling enhances recovery of strength and reduces soreness following eccentric exercise. Importantly, these data show for the first time that prolonged PCM cooling does not compromise the adaptive response associated with the RBE.

Comparison among three different intensities of eccentric contractions of the elbow flexors resulting in the same strength loss at one day post-exercise for changes in indirect muscle damage markers

PURPOSE

The present study compared three different intensity elbow flexor eccentric exercises resulting in the same magnitude of maximal voluntary isomeric contraction torque (MVC) decrease at 1 day post-exercise for changes in several indirect markers of muscle damage and proprioception.

METHODS

Sedentary young men performed eccentric contractions of the elbow flexors using a dumbbell corresponding to either 10%, 50% or 100% of MVC to induce ~ 20% decrease in MVC at 1 day post-exercise (n = 12/group). MVC, range of motion (ROM), upper arm circumference (CIR), muscle soreness, plasma creatine kinase (CK) activity, and proprioception measures (force match, joint position sense) were taken before to 5 days after exercise, and the changes were compared among the groups.

RESULTS

MVC and ROM recovered faster (P < 0.05) in the order of 10% (e.g., 3 days post-exercise: - 3 ± 4%, 0 ± 1%), 50% (- 12 ± 3%, - 3 ± 2%) and 100% group (- 16 ± 4%, - 5 ± 1%). Peak CIR, muscle soreness and CK activity were smaller for 10% (Δ3 ± 1 mm, 26 ± 10 mm, 1049 ± 316 IU/L) than 50% (Δ6 ± 2 mm, 36 ± 14 mm, 1473 ± 429 IU/L) and 100% groups (Δ8 ± 2 mm, 47 ± 15 mm, 2104 ± 929 IU/L). The proprioception measures recovered faster (P < 0.05) for 10% followed by 50% then 100% group. The recovery rate of MVC from immediately to 1 day post-exercise was correlated (P < 0.05) with the changes in the muscle damage and proprioception markers.

CONCLUSION

These results suggest that the MVC at 1 day post-exercise does not necessarily predict the changes in muscle damage markers in the following days, but the MVC recovery rate in the first 24 h reflects the magnitude of muscle damage better.

Effects of mirthful laughter on pain tolerance: A randomized controlled investigation

INTRODUCTION

Chronic pain is a debilitating condition that affects many people. Currently, there is no single treatment known to cure or assure relief from chronic pain. Accordingly, the management of patients' discomfort is an integral part of treating chronic pain. Such treatment, however, is not effective for many patients. We investigated whether mirthful laughter provided by comic relief can influence pain tolerance and muscle soreness in young healthy participants.

METHODS

Forty participants underwent a randomized controlled cross-over designed experiment. Each participant was exposed to a comedy video eliciting mirthful laughter and an uninteresting documentary. Delayed onset muscle soreness was induced in one leg at a time by eccentric exercise. Pain tolerance was tested using blunt force application and assessed subjectively using a visual analog scale.

RESULTS

Watching the comedy video elicited a significantly greater irregular breathing pattern compared with watching the documentary video (p < 0.001). After watching the comedy, the participants' positive affect was increased (Δ2 ± 1) while it was largely decreased (Δ-11 ± 2) after watching the documentary video (p < 0.001). Pain tolerance was decreased by 17 ± 5 N after viewing the documentary video (p < 0.001), but did not change significantly after watching the comedy.

CONCLUSIONS

Thirty minutes of watching a comedy eliciting laughter favorably influenced pain tolerance in healthy humans. CLINICAL TRIAL NO.: #NCT02896075.

AmLexin, a Standardized blend of Acacia catechu and Morus alba, shows benefits to delayed onset muscle soreness in healthy runners

[Purpose]

Sudden and exhaustive exercise causes muscle damage accompanied by oxidative stress and inflammation, leading to muscle fatigue and soreness. AmLexin contains a standardized blend of extracts from the heartwood of Acacia catechu and the root bark of Morus alba, and is known to possess antioxidant and anti-inflammatory properties. The aim of this study was to investigate the effects of this proprietary blend supplementation on muscular pain and redox balance in healthy runners, in comparison to a placebo.

[Methods]

A double-blind placebo-controlled clinical trial was carried out over 9 weeks in a single center. Thirty physically active male and female subjects within 18−70 years of age were randomized into AmLexin (mean age = 42.92 ± 2.48 and gender 7/5, male/female, respectively) and placebo (mean age = 41.15 ± 3.5 and gender 10/3, male/female, respectively) groups. Subjects were supplemented with 400 mg of AmLexin/day or a look-alike placebo during an 8-week training program, and for one week following a 13.1-mile half-marathon. Twenty-six subjects completed the 9-week supplementation trial.

[Results]

Results showed the AmLexin group experienced significantly lower levels of post-exercise pain on day 1−3 following the half-marathon compared to the placebo group. The AmLexin group also showed lower post-exercise oxidative stress and higher antioxidant capacity on days 1 and 6 following the half-marathon. These results demonstrated the rapid benefits of AmLexin on pain and oxidative stress within 1−6 days post-exercise.

[Conclusion]

Our data suggest that AmLexin could be a safe, effective botanical alternative for delayed onset muscle soreness.

The effect of intermittent lower limb occlusion on recovery following exercise-induced muscle damage: A randomized controlled trial

OBJECTIVES

The purpose of this investigation was to examine the effectiveness of intermittent lower limb occlusion in augmenting recovery from exercise induced muscle damage (EIMD) in physically active males.

DESIGN

Randomized controlled trial, double blind.

METHODS

Sixteen healthy recreationally active male participants were randomly assigned to an intermittent occlusion (OCC; n=8) or control (SHAM; n=8) group. The EIMD protocol comprised of 100 drop-jumps, from a 0.6m box. Indices of muscle damage were creatine kinase (CK), thigh-circumference (TC), muscle soreness (DOMS), counter-movement jump (CMJ) and maximal isometric voluntary contraction (MIVC). Measurements were assessed pre, 24h, 48h and 72h following exercise.

RESULTS

There was a significant time effect for all indices of muscle damage suggesting EIMD was present following the exercise protocol. The decrease in MIVC was significantly attenuated in the OCC group compared to the SHAM group at 24 (90.4±10.7 vs. 81.5±6.7%), 48 (96.2±6.1 vs. 84.5±7.1%) and 72h (101.1±4.2 vs. 89.7±7.5%). The CK response was reduced in the OCC group at 24 (335±87 vs. 636±300 IU) and 48h (244±70 vs. 393±248 IU), compared to the SHAM group. DOMS was significantly lower in the OCC compared to the SHAM group at 24, 48 and 72h post EIMD. There was no effect of OCC on CMJ or TC.

CONCLUSIONS

This investigation shows that intermittent lower limb occlusion administered after a damaging bout of exercise reduces indices of muscle damage and accelerates the recovery in physically active males.

Herbs and natural supplements in the prevention and treatment of delayed-onset muscle soreness

OBJECTIVE

Unaccustomed and intense eccentric exercise is a common cause of delayed-onset muscle soreness (DOMS). There are multiple remedies for the treatment of DOMS, but its clinical and laboratory pieces of evidence are scarce. Currently, the treatments proposed for DOMS are numerous and include pharmaceuticals, herbal remedies, stretching, massage, nutritional supplements, and other alternatives. To find a holistic treatment with effective pain relief and minimum side effects, complementary and alternative medicine, including herbal therapies, plays a main role.

METHODS

In this review, the existing published studies investigating the efficacy of herbal and natural supplementation therapies for the prevention or treatment of side effects, symptoms, and signs of DOMS are summarized.

RESULTS

Previous studies have documented the efficacy of herbal therapies to treat pain, inflammation, as well as laboratory and clinical side effects of DOMS.

CONCLUSION

The use of herbs in DOMS seems safer and has lower side effects than pharmacotherapy. However, the potential for side effects and drug interactions should be considered.

Differences in post-exercise T2 relaxation time changes between eccentric and concentric contractions of the elbow flexors

PURPOSE

This study compared maximal eccentric (ECC) and concentric (CON) contractions of the elbow flexors for changes in transverse relaxation time (T2) and indirect markers of muscle damage.

METHODS

Twelve young men performed five sets of six maximal isokinetic (30°/s) ECC with one arm followed by CON with the other arm. Magnetic resonance images to assess T2 and cross-sectional area (CSA) of biceps brachii, brachialis, and brachioradialis, and measurements of maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), and muscle soreness were taken before, immediately after, and 1, 3, and 5 days after each exercise.

RESULTS

MVC torque and ROM decreased greater after ECC than CON (p < 0.05), and muscle soreness developed only after ECC. Biceps brachii and brachialis CSA increased immediately after CON, but delayed increases in brachialis CSA were found only after ECC (p < 0.05). T2 of the muscles increased greater after CON (27-34 %) than ECC (16-18 %) immediately post-exercise (p < 0.05), but returned to baseline by 1 day after CON. The biceps brachii and brachialis T2 increased by 9-29 % at 1-5 days after ECC (p < 0.05). The post-ECC T2 changes showed no significant correlations with the changes in MVC torque, muscle soreness, and CSA, but the T2 increase immediately post-ECC was correlated with the peak T2 in 1-5-day post-ECC (r = 0.63, p < 0.05).

CONCLUSION

These results suggest that muscle activity during exercise was lower in ECC than CON, and the T2 changes after ECC do not necessarily relate to the changes in other indirect markers of muscle damage.

Does degree of alteration in effort sense caused by eccentric exercise significantly affect initial exercise hyperpnea in humans?

Previous research has shown an exaggeration in exercise hyperpnea 2 days after eccentric exercise (ECC). Enhancement in central command has been suggested as one candidate to account for this effect given that ECC-induced neuromuscular dysfunction increases relative exercise intensity, thus resulting in reinforcement of effort sense. The purpose of this study was, therefore, to elucidate whether the degree of alteration in effort sense caused by ECC affects exercise hyperpnea. Ten subjects performed 20-s single-arm extension-flexion exercises with weight strapped to the wrist, and ventilatory response was measured before (Pre) and 2 days after ECC (D2). Relative exercise intensity at Pre was 5 % of maximal voluntary contraction (MVC) of Pre, whereas that at D2 was 9 % MVC of D2 because of decline in muscle strength. Ventilatory responses were significantly exaggerated at D2 with a significant increase in effort sense. Although effort sense was significantly reduced during exercise at D2 when wrist weight was subtracted to match relative exercise intensity at Pre (5 % MVC of D2), ventilatory responses were still significantly higher than those of Pre. After the disappearance of post-ECC muscle damage, subjects performed the same exercise with weight added (9 % MVC of Pre) so that effort was equalized to match that of D2; however, no significant increase in ventilatory response was detected. The fact that the extent of change in effort sense caused by ECC-induced neuromuscular dysfunction did not affect ventilatory response at the onset of exercise after ECC may suggest that the exaggeration of ventilatory response after ECC is caused by mechanisms other than alteration of the central command.

Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing

Prolonged unaccustomed exercise involving muscle lengthening (eccentric) actions can result in ultrastructural muscle disruption, impaired excitation-contraction coupling, inflammation and muscle protein degradation. This process is associated with delayed onset muscle soreness and is referred to as exercise-induced muscle damage. Although a certain amount of muscle damage may be necessary for adaptation to occur, excessive damage or inadequate recovery from exercise-induced muscle damage can increase injury risk, particularly in older individuals, who experience more damage and require longer to recover from muscle damaging exercise than younger adults. Furthermore, it is apparent that inter-individual variation exists in the response to exercise-induced muscle damage, and there is evidence that genetic variability may play a key role. Although this area of research is in its infancy, certain gene variations, or polymorphisms have been associated with exercise-induced muscle damage (i.e. individuals with certain genotypes experience greater muscle damage, and require longer recovery, following strenuous exercise). These polymorphisms include ACTN3 (R577X, rs1815739), TNF (-308 G>A, rs1800629), IL6 (-174 G>C, rs1800795), and IGF2 (ApaI, 17200 G>A, rs680). Knowing how someone is likely to respond to a particular type of exercise could help coaches/practitioners individualise the exercise training of their athletes/patients, thus maximising recovery and adaptation, while reducing overload-associated injury risk. The purpose of this review is to provide a critical analysis of the literature concerning gene polymorphisms associated with exercise-induced muscle damage, both in young and older individuals, and to highlight the potential mechanisms underpinning these associations, thus providing a better understanding of exercise-induced muscle damage.

The comparison of cold-water immersion and cold air therapy on maximal cycling performance and recovery markers following strength exercises

This study examined the effects of cold-water immersion (CWI) and cold air therapy (CAT) on maximal cycling performance (i.e. anaerobic power) and markers of muscle damage following a strength training session. Twenty endurance-trained but strength-untrained male (n = 10) and female (n = 10) participants were randomised into either: CWI (15 min in 14 °C water to iliac crest) or CAT (15 min in 14 °C air) immediately following strength training (i.e. 3 sets of leg press, leg extensions and leg curls at 6 repetition maximum, respectively). Creatine kinase, muscle soreness and fatigue, isometric knee extensor and flexor torque and cycling anaerobic power were measured prior to, immediately after and at 24 (T24), 48 (T48) and 72 (T72) h post-strength exercises. No significant differences were found between treatments for any of the measured variables (p > 0.05). However, trends suggested recovery was greater in CWI than CAT for cycling anaerobic power at T24 (10% ± 2%, ES = 0.90), T48 (8% ± 2%, ES = 0.64) and T72 (8% ± 7%, ES = 0.76). The findings suggest the combination of hydrostatic pressure and cold temperature may be favourable for recovery from strength training rather than cold temperature alone.

Effects of the hold and relax-agonist contraction technique on recovery from delayed onset muscle soreness after exercise in healthy adults

[Purpose] This study was conducted to verify the effects of the hold relax-agonist contraction and passive straight leg raising techniques on muscle activity, fatigue, and range of motion of the hip joint after the induction of delayed onset muscle soreness in the hamstring muscle. [Subjects] Sixty subjects were randomly assigned to a hold relax-agonist contraction group and a passive straight leg raising group. [Methods] Subjects in the experimental group underwent hold relax-agonist contraction at the hamstring muscle, while subjects in the control group underwent passive straight leg raising at the hamstring muscle. [Results] Subjects in the hold relax-agonist contraction group showed a significant increase in hamstring muscle activity and hip joint angle and a significant decrease in muscle fatigue. In the passive straight leg raising group, the hip joint angle increased significantly after the intervention. In the hold relax-agonist contraction group, hamstring muscle activity increased significantly and muscle fatigue decreased significantly. [Conclusion] We conclude that the hold relax-agonist contraction technique may be beneficial for improving muscle activation and decreasing muscle fatigue.

Development of a non-damaging high-intensity intermittent running protocol

The aim of the present study was to devise a non-damaging high-intensity intermittent running protocol. Ten healthy active men completed high-intensity interval running (8× 3-min bouts at 90% of maximal oxygen uptake interspersed with 3-min recovery) on a motorized treadmill under normal laboratory temperatures. Mean heart rate and rating of perceived exertion significantly increased during the intermittent protocol (the first bout, 15.3± 1.2; the final bout, 18.6± 0.9; P< 0.001). Blood lactate concentrations were significantly elevated following bout 1 compared with resting values (1.2± 0.3 mmol/L vs 5.4± 2.4 mmol/L; P = 0.03). However, no significant reduction in maximal voluntary contraction was observed immediately after completing the last exercise bout (623.9± 143.6 N) or during the subsequent 7-d period compared to pre-exercise values (P = 0.59). Creatine kinase (CK) concentrations were not significantly increased following exercise or during the subsequent 7-d period (P = 0.96). Myoglobin (Mb) content was significantly increased following exercise (P = 0.01), however, values returned towards pre-exercise concentrations after 24 h. These results indicate that the high-intensity intermittent running protocol induced changes in physiological and subjective indices that are consistent with the effects of acute fatigue as opposed to those changes normally associated with exercise-induced muscle damage. This exercise protocol can therefore be used to investigate the influence of high-intensity exercise from physiological responses to molecular adaptation.

A review of nutritional intervention on delayed onset muscle soreness. Part I

This review is focused on the effect of nutritional intervention on delayed onset muscle soreness (DOMS) that occurs after exercise. In general, high force eccentric contractions and/or unaccustomed exercise result in DOMS attributed to reduction in performance such as muscle strength and range of motion (ROM) for both athletes and non-athletes. Nutritional intervention is one of the preventive or therapeutic ways to reduce DOMS. Previous research studies have suggested the following nutrition intervention: caffeine, omega-3 fatty acids, taurine, polyphenols, and so on. Nutritional intervention with these nutrients before and after exercise was reported to be effective in reducing DOMS. These nutritional interventions have also been reported to affect inflammatory responses and oxidative stress leading to DOMS reduction. However, other studies have reported that these nutritional interventions have no effect on DOMS. It is suggested that intake of proper nutrition intervention can effectively reduce DOMS after exercise and quickly help an athlete return to exercise or training program. In addition, nutritional intervention may help both athletes and non-athletes who engage in physical therapy or rehabilitative programs after surgery or any injurious events.

Effects of therapeutic massage on gait and pain after delayed onset muscle soreness

Unfamiliar or sudden exercise can induce delayed onset muscle soreness (DOMS) within 12–24 h. So, several researchers have reported various interventions to treat DOMS. Massage is generally known to eliminate muscle fatigue. However, effect of massage after DOMS is still not clear. We investigated whether the massage is effective on pain and gait after DOMS. The participants were divided into a control group (n= 10) with DOMS and an experimental group (n= 11) with the massage treated after DOMS. We induced DOMS by taking isotonic exercise with going up and down 20 times in 5-story building. We applied the massage and assessment on gastrocnemius of dominant foot. The change of gait and pain was assessed using gaitrite and algometer. In the present results, the massage on gastrocnemius after DOMS showed significant difference in pain (P< 0.05). Also, there was a significant difference in gait (P< 0.05), especially, spatial parameters (distance, step length, stride length) and temporal parameters (ambulation, heel on off time, stride velocity). Moreover, the pain relief after massage-treated in DOMS correlated with gait. These results suggest that the massage on gastrocnemius after DOMS has influence on pain and gait performance. Therefore, massage can be applied as intervention for delayed onset muscle soreness.

Systemic cytokine response to three bouts of eccentric exercise

This research examined the changes in inflammatory cytokines interleukin 6 (IL-6), IL-1ß, IL-10, as well as muscle force, muscle soreness, thigh circumference, and range of motion in response to 3 bouts of eccentric knee extension. Ten males were recruited to participate. The participants performed eccentric exercise on 3 consecutive days on the knee extensors on the right leg separated by 24??h. Participants performed 6 sets of 10 repetitions of isokinetic eccentric knee extension at 120° per second. Blood was sampled before and after each exercise bout and 24?h after the final exercise bout. Muscle isometric force, delayed onset muscle soreness (DOMS), thigh circumference, and range of motion were evaluated before and after each exercise bout and 24?h after the final exercise bout. There were no statistically significant differences noted for the changes in isometric strength, thigh circumference, and range of motion, or IL-6 over the 4 days (all p > 0.05). On the second day and third day there was a significant increase noted in DOMS as compared with baseline (p < 0.05). These results suggest that 3 consecutive days of eccentric exercise results in DOMS but does not produce a sustained systemic inflammatory reaction or changes in muscle function.

The effects of anatabine on non-invasive indicators of muscle damage: a randomized, double-blind, placebo-controlled, crossover study

Background

Anatabine (ANA), a minor tobacco alkaloid found in the Solanaceae family of plants, may exhibit anti-inflammatory activity, which may be useful to aid in recovery from exercise-induced muscle damage. The purpose of this study, therefore, was to examine the effects of ANA supplementation on the recovery of isometric strength and selected non-invasive indicators of muscle damage.

Methods

A double-blinded, placebo-controlled, crossover design was used to study eighteen men (mean ± SD age = 22.2 ± 3.1 yrs; body mass = 80.3 ± 15.7 kg) who participated in two randomly-ordered conditions separated by a washout period. The ANA condition consisted of consuming 6–12 mg anatabine per day for 10 days, while testing took place during days 7–10. The placebo (PLA) condition was identical except that the PLA supplement contained no ANA. Maximal voluntary isometric peak torque (PT) of the forearm flexors, arm circumference, hanging joint angle, and subjective pain ratings were measured before (PRE), immediately after (POST), and 24, 48, and 72 h after six sets of 10 maximal, eccentric isokinetic forearm flexion muscle actions. Resting heart rate and blood pressure were measured at PRE and 72 h in each condition.

Results

For PT, hanging joint angle, arm circumference, and subjective pain ratings, there were no condition x time (p > 0.05) interactions, there were no main effects for condition (p > 0.05), but there were main effects for time (p < 0.001). There were no condition x time (p > 0.05) interactions and no main effects for condition (p > 0.05) or time (p > 0.05) for blood pressure or resting heart rate.

Conclusions

ANA supplementation had no effect on the recovery of muscle strength, hanging joint angle, arm swelling, or subjective pain ratings after a bout of maximal eccentric exercise in the forearm flexors. Therefore, ANA may not be beneficial for those seeking to improve recovery from heavy eccentric exercise. Future studies should examine the effects of ANA on the pro-inflammatory cytokine responses to exercise-induced muscle damage and the chronic low-grade inflammation observed in obese and elderly individuals.