Bout Of Eccentric Exercise Research Articles

Changes in motor unit behaviour across repeated bouts of eccentric exercise.

Unaccustomed eccentric exercise (EE) is protective against muscle damage following a subsequent bout of similar exercise. One hypothesis suggests the existence of an alteration in motor unit (MU) behaviour during the second bout, which might contribute to the adaptive response. Accordingly, the present study investigated MU changes during repeated bouts of EE. During two bouts of exercise where maximal lengthening dorsiflexion (10 repetitions × 10 sets) was performed 3weeks apart, maximal voluntary isometric torque (MVIC) and MU behaviour (quantified using high-density electromyography; HDsEMG) were measured at baseline, during (after set 5), and post-EE. The HDsEMG signals were decomposed into individual MU discharge timings, and a subset were tracked across each time point. MVIC was reduced similarly in both bouts post-EE (Δ27 vs. 23%, P=0.144), with a comparable amount of total work performed (∼1,300 J; P=0.905). In total, 1,754 MUs were identified and the decline in MVIC was accompanied by a stepwise increase in discharge rate (∼13%; P<0.001). A decrease in relative recruitment was found immediately after EE in Bout 1versus baseline (∼16%; P<0.01), along with reductions in derecruitment thresholds immediately after EE in Bout 2. The coefficient of variation of inter-spike intervals was lower in Bout 2 (∼15%; P<0.001). Our data provide new information regarding a change in MU behaviour during the performance of a repeated bout of EE. Importantly, such changes in MU behaviour might contribute, at least in part, to the repeated bout phenomenon.

Temporal tracking of cysteine 34 oxidation of plasma albumin as a biomarker of muscle damage following a bout of eccentric exercise

PurposeExercise-induced muscle damage (EIMD) results in the generation of reactive oxygen species (ROS), but little is known about the temporal profile of change in ROS post-EIMD and how ROS levels relate to the onset of and recovery from EIMD. Our primary aim was to examine the effect of EIMD on the pattern of change in the blood level of thiol-oxidised albumin, a marker of oxidative stress.MethodsSeven male participants were subjected on separate days to eccentric muscle contraction to cause EIMD or a no-exercise condition. After each session, the participants collected daily dried blood spots to measure thiol-oxidised albumin and returned to the laboratory every 2 days for the assessment of indirect markers of EIMD, namely maximal voluntary contraction (MVC), delayed onset muscle soreness (DOMS), creatine kinase (CK), and myoglobin.ResultsEccentric exercise resulted in a significant decrease in MVC and increase in DOMS, CK, myoglobin, and thiol-oxidised albumin with the latter reaching above baseline level within 24–48 h post-exercise. All the markers of EIMD returned to baseline level within 6 days post-exercise, but not the level of thiol-oxidised albumin which remained elevated for 10 days after exercise. There was a moderate correlation between changes in thiol-oxidised albumin and DOMS, but no significant relationship between any other markers of muscle damage.ConclusionThe levels of thiol-oxidised albumin increase in response to EIMD and remain elevated for several days post-exercise. The temporal pattern of change in the level of thiol-oxidised albumin suggests that this may be a useful biomarker of muscle repair post-EIMD.

Effects of single and multiple bouts of eccentric exercise on immune responses to HSV-gD1 DNA vaccination in mice

Abstract DNA vaccines comprise one modality of novel vaccination techniques. DNA vaccines employ intramuscular injection of DNA that codes for specific antigens from a pathogen. Prolonged eccentric endurance exercise can stimulate immune responses, possibly by increasing inflammatory mediators. This study aimed to determine the effects of one or three sessions of downhill running on the effectiveness of Herpes simplex virus type I glycoprotein D (HSV-gD1) DNA vaccination. Mice without or with one and three sessions of downhill running were vaccinated intramuscularly with the DNA vaccine or the empty vector. Cellular immune responses were assessed using an in vitro assay of lymphocyte proliferation in response to recall antigens. Also, a virus neutralisation test was used to determine the levels of neutralising antibodies in serum samples. In addition, Th1 and Th2 immune responses, and the ratio of the Th1/Th2 is considered an indicator of immune responses to infection in the current study. Multiple bouts of downhill running increased humoral immune responses after immunisation, also although Th2 immune responses decreased, lymphocyte proliferation and Th1/Th2 ratio immune responses increased following the viral challenge compared to the other groups. In addition, the timing of the 3-session exercise regimen plus DNA vaccination immediately following the last exercise session, as opposed to DNA vaccination 48 h before a single session of exercise, may account for the greater efficacy of DNA vaccination in the multiple bouts of the intensive exercise group. These findings indicate that short-term repeated bouts of eccentric endurance exercise have increased immune responses to intramuscular DNA-based vaccines.

Fish oil supplementation fails to modulate indices of muscle damage and muscle repair during acute recovery from eccentric exercise in trained young males

ABSTRACT We aimed to investigate the influence of 4-wk of fish oil (FO) supplementation on markers of muscle damage, inflammation, muscle soreness, and muscle function during acute recovery from eccentric exercise in moderately trained males. Sixteen moderately-trained males ingested 5 g/d of FO (n = 8) or soybean oil (placebo) capsules (n = 8) for 4-wk prior to- and 3-d following an acute eccentric exercise bout. Eccentric exercise consisted of 12 sets of isokinetic knee extension and knee flexion. Indices of muscle damage, soreness, function and inflammation were measured at baseline and during exercise recovery. Eccentric exercise elicited an increase in muscle soreness (p < 0.010) and thigh volume (p < 0.001), and reduced peak isometric torque by 31.7 ± 6.9%, (p < 0.05, 95% CI 10.6–52.8) during 3-d of recovery. Blood omega-3 polyunsaturated fatty acid concentration was 14.9 ± 2.4% higher in FO than PLA (p < 0.01, 95% CI 9.8–20.1). However, FO did not ameliorate the cumulative creatine kinase response (expressed as AUC; p = 0.368), inflammation (p = 0.400), muscle soreness (p > 0.140), or muscle function (p > 0.249) following eccentric exercise. FO supplementation confers no clear benefit in terms of ameliorating the degree of muscle damage, or facilitating the muscle repair process, during acute eccentric exercise recovery. These data suggest that FO supplementation does not provide an effective nutritional strategy to promote exercise recovery, at least in moderately-trained young men. Abbreviations: ANOVA: Analysis of variance; AUC: Area under curve; CI: Confidence interval; CK: Creatine kinase; CMJ: Countermovement jump; COX: Cyclooxygenase; CRP: C-reactive protein; DHA: Docosahexaenoic acid; DOMS: Delayed-onset muscle soreness; EIMD: Exercise-induced muscle damage; En%: Energy percent; EPA: Eicosapentaenoic acid; FO: Fish oil; IL-6: Interleukin-6; LDH: Lactate dehydrogenase; LOX: Lipoxygenase; Mb: Myoglobin; mTOR: Mechanistic target of rapamycin; PLA: Placebo; ROM: Range of motion; ROS: Reactive oxygen species; SD: Standard deviation; SEM: Standard error of the mean; TNF-α: Tumour necrosis factor alpha; VAS: Visual analogue scale; Ω3-PUFA: Omega-3 polyunsaturated fatty acids; Ω6-PUFA: Omega-6 polyunsaturated fatty acids Highlights The anti-inflammatory properties of omega-3 polyunsaturated fatty acids, alongside their propensity to incorporate into the muscle phospholipid membrane underpins the idea that fish oil supplementation may attenuate muscle damage and promote muscle repair following eccentric-based exercise. Four weeks of high-dose (5 g/d) fish oil supplementation prior to eccentric exercise failed to attenuate the rise in creatine kinase concentration and muscle soreness during acute exercise recovery in physically-active young men. Future studies are warranted to investigate the efficacy of combining omega-3 polyunsaturated fatty acids with other nutrients (i.e. protein/amino acids) for the promotion of muscle recovery following eccentric-based damaging exercise.

Astaxanthin Supplementation Reduces Subjective Markers of Muscle Soreness following Eccentric Exercise in Resistance-Trained Men

Strenuous exercise involving eccentric muscle actions induces skeletal muscle damage resulting in delayed onset muscle soreness (DOMS). Antioxidant supplementation, such as astaxanthin (AX), may alleviate muscle injury following intense exercise. The purpose of this study was to investigate the effect of a four-week course of AX supplementation at 12 mg/day−1 on subjective markers of DOMS, recovery, and performance after a bout of muscle damaging eccentric exercise. Nineteen resistance-trained men (mean ± SD: age, 22.6 ± 2.2 y) completed a between-group design with a four-week supplementation period of 12 mg/day−1 of either AX or a placebo. Subjects completed four trials, with trials One and Three designed to induce muscle damage, consisting of a one repetition maximum test (1RM) for leg-press, followed by five sets of ten repetitions at 65% of 1RM. Trials Two and Four were performance trials, conducted 48 h later and consisting of repetitions to failure at 65%, 70%, and 75% of 1RM. Subjective markers of DOMS and recovery were collected at multiple timepoints post-trial for trials One and Three. Although performance was not affected (p &gt; 0.05), AX supplementation significantly decreased subjective markers of DOMS (p = 0.01) compared to the placebo. The results demonstrated that AX may enhance recovery by reducing DOMS without detriment to performance in resistance-trained men.

Increased muscle force does not induce greater stretch-induced damage to calf muscles during work-matched heel drop exercise

PurposeTo investigate the effect of muscle force during active stretch on quantitative and qualitative indicators of exercise-induced muscle damage (EIMD) in the medial gastrocnemius (MG) muscle.MethodsTwelve recreationally active volunteers performed two trials of an eccentric heel drop exercise. Participants performed a single bout of low-load (body weight) and high-load (body weight + 30% body weight) exercises on separate legs. The total mechanical work output for each condition was matched between legs. Before, two hours and 48 h after each bout of eccentric exercise, electrically stimulated triceps surae twitch torque, muscle soreness, MG active fascicle length at maximum twitch torque and muscle passive stiffness were collected. Triceps surae electromyographic (EMG) activity, MG fascicle stretch and MG muscle–tendon unit (MTU) length were measured during the eccentric tasks.ResultsThe high-load condition increased triceps surae muscle activity by 6–9%, but reduced MG fascicle stretch (p < 0.001). MTU stretch was similar between conditions. The greater muscle force during stretch did not give rise to additional torque loss (5 vs 6%) or intensify muscle soreness.ConclusionsAdding 30% body weight during eccentric contractions has a modest impact on exercise-induced muscle damage in the medial gastrocnemius muscle. These results suggest that muscle load may not be an important determinant of stretch-induced muscle damage in the human MG muscle. The muscle investigated does exhibit large pennation angles and high series elastic compliance; architectural features that likely buffer muscle fibres against stretch and damage.

Blood Pressure Responses to Postexercise Circulatory Occlusion Are Attenuated After Exercise-Induced Muscle Weakness.

Exercise blood pressure (BP) responses are thought to be determined by relative exercise intensity (percent maximal voluntary contraction (MVC) strength). However, cross-sectional studies report that during a static contraction, higher absolute force is associated with greater BP responses to relative intensity exercise and subsequent muscle metaboreflex activation with postexercise circulatory occlusion (PECO). We hypothesized that a bout of unaccustomed eccentric exercise would reduce knee extensor MVC and subsequently attenuate BP responses to PECO. Continuous BP, heart rate, muscle oxygenation, and knee extensor electromyography were recorded in 21 young healthy individuals (female, n = 10) during 2 min of 20% MVC static knee extension exercise and 2 min of PECO, performed before and 24 h after 300 maximal knee extensor eccentric contractions to cause exercise-induced muscle weakness. As a control, 14 participants repeated the eccentric exercise 4 wks later to test whether BP responses were altered when exercise-induced muscle weakness was attenuated via the protective effects of the repeated bout effect. Eccentric exercise reduced MVC in all participants (144 ± 43 vs 110 ± 34 N·m, P < 0.0001). BP responses to matched relative intensity static exercise (lower absolute force) were unchanged after eccentric exercise ( P > 0.99) but were attenuated during PECO (systolic BP: 18 ± 10 vs 12 ± 9 mm Hg, P = 0.02). Exercise-induced muscle weakness modulated the deoxygenated hemoglobin response to static exercise (64% ± 22% vs 46% ± 22%, P = 0.04). When repeated after 4 wks, exercise-induced weakness after eccentric exercise was attenuated (-21.6% ± 14.3% vs -9.3 ± 9.7, P = 0.0002) and BP responses to PECO were not different from control values (all, P > 0.96). BP responses to muscle metaboreflex activation, but not exercise, are attenuated by exercise-induced muscle weakness, indicating a contribution of absolute exercise intensity on muscle metaboreflex activation.

The Contralateral Repeated Bout Effect of Elbow Flexors Is Not Observed in Young Women Following Mild Muscle Damage from Eccentric Exercises.

Investigation of the contralateral repeated bout effect (CL-RBE) in women is scarce. Therefore, this study aimed at examining whether CL-RBE exists in women. Twelve healthy women (age: 20.9 ± 2.5 years) performed two bouts of maximal elbow flexor eccentric exercise (3 sets × 15 repetitions per bout) separated by 14 days, using the opposite arms. Surface Electromyography (EMG) was recorded during both exercise bouts. The isokinetic muscle strength (60°/s), muscle soreness, range of motion (ROM), limb girth, and blood creatine kinase activity were measured pre-exercise, and at 24 and 48 h post-exercise with the muscle strength being measured immediately post-exercise as well. Significant main effects of time were observed for muscle strength, muscle soreness and ROM (p < 0.05). There were no significant differences between bouts for all the measured variables including the EMG median frequency (p > 0.05). These results suggest that the CL-RBE of elbow flexors was not evident in young healthy women. This was because the mild muscle damage induced by the initial bout of exercise was either not enough to initiate the CL-RBE or the CL-RBE in women lasted shorter than two weeks. This study provides important information for future studies on CL-RBE in women.

Almond intake alters the acute plasma dihydroxy-octadecenoic acid (DiHOME) response to eccentric exercise.

This investigation determined if 4-weeks ingestion of nutrient-dense almonds mitigated post-exercise inflammation and muscle soreness and damage. An acute 90-min of eccentric exercise (90-EE) was used to induce muscle damage in 64 non-obese adults not engaging in regular resistance training (ages 30-65 years, BMI < 30 kg/m2). Using a parallel group design, participants were randomized to almond (AL) (57 g/d) or cereal bar (CB) (calorie matched) treatment groups for a 4-week period prior to the 90-EE (17 exercises). Blood and 24-h urine samples were collected before and after supplementation, with additional blood samples collected immediately post-90-EE, and then daily during 4 additional days of recovery. Changes in plasma oxylipins, urinary gut-derived phenolics, plasma cytokines, muscle damage biomarkers, mood states, and exercise performance were assessed. The 90-EE protocol induced significant muscle damage, delayed onset of muscle soreness (DOMS), inflammation, reduced strength and power performance, and mood disturbance. Interaction effects (2 group × 7 time points) supported that AL vs. CB was associated with reduced post-exercise fatigue and tension (p = 0.051, 0.033, respectively) and higher levels of leg-back strength (p = 0.029). No group differences were found for post-90-EE increases in DOMS and six cytokines. AL was associated with lower levels of serum creatine kinase immediately- and 1-day post-exercise (p = 0.034 and 0.013, respectively). The 90-EE bout increased plasma levels immediately post-exercise for 13 oxylipins. Interaction effects revealed significantly higher levels for AL vs. CB for 12,13-DiHOME (p < 0.001) and lower levels for 9,10-DiHOME (p < 0.001). Urine levels increased in AL vs. CB for seven gut-derived phenolics including 5-(3',4'-dihydroxyphenyl)-γ-valerolactone that was inversely related to changes in plasma 9,10-DiHOME (r = -0.029, p = 0.021). These data support some positive effects of almond intake in improving mood state, retaining strength, decreasing muscle damage, increasing the generation of gut-derived phenolic metabolites, and altering the plasma oxylipin DiHOME response to unaccustomed eccentric exercise in untrained adults. The elevated post-exercise plasma levels of 12,13-DiHOME with almond intake support positive metabolic outcomes for adults engaging in unaccustomed eccentric exercise bouts.

Protective effect of N-acetyl cysteine on vascular function of young individuals after a bout of resistance exercise: a randomized placebo-controlled study

Abstract Background High intensity resistance exercise may temporarily induce vascular dysfunction mediated by pro-oxidant and pro-inflammatory pathways. Whether antioxidant supplements ameliorate this dysfunction has not been clarified. Purpose In the present study we aimed to evaluate the effect of the antioxidant N-acetyl cysteine (NAC) on vascular function after a bout of high-intensity resistance exercise in healthy young individuals. Methods In this randomized, cross-over, placebo-controlled study, ten healthy male volunteers (mean age 24.2±2.1 years) who exercised regularly were randomized to a daily oral administration of NAC or placebo during an 8-day recovery after an acute intense eccentric exercise protocol. In order to estimate changes in vascular parameters of interest -pulse wave velocity (PWV) and flow-mediated dilation (FMD)-, measurements were performed pre-exercise and across 6 pre-specified time points post-exercise (from 2 to 120 hours) in both arms. Blood samples were collected at baseline, immediately after exercise, 2 hours after exercise, and daily for eight consecutive days thereafter for the measurement of cellular components of the immune system. Results Muscle exercise induced a significant decrease in FMD in the placebo arm (F=2.74, p=0.017). This phenomenon was evident until 48 hours after exercise while FMD progressively returned to baseline values thereafter. In contrast, in the NAC arm, FMD did not decrease significantly (p&amp;gt;0.05 for all time-points). By linear mixed model analysis, a higher increase in CD4 cells levels correlated with preserved FMD (coefficient=0.025, p=0.046) in the placebo arm whereas this association was not significant (coefficient=0.004, p=0.811) in the NAC arm. PWV did not present significant fluctuations before and after exercise in either arm (p&amp;gt;0.05 for all comparisons). Conclusion A bout of eccentric exercise in young regularly training individuals induced endothelial dysfunction peaking at 48 hours, possibly partly mediated by an attenuated CD4 response. NAC exerted protective action on FMD, indicating that oxidative stress may be implicated in vivo in this setting. Funding Acknowledgement Type of funding sources: None.

VP.89 Skeletal muscle after a single bout of eccentric exercise in myotonic dystrophy type 1: a complete proteomic analysis

Myotonic dystrophy type 1 (DM1) is a multisystemic progressive genetic disease that causes muscle weakness and wasting. Strength training has been shown to be safe and can induce maximal strength gains. However, the underlying molecular mechanisms of these maximal strength gains remain unclear. The aim of this study is to determine how a single bout of eccentric exercise modulates protein expression in DM1 individuals compared to controls. Eight men with DM1 and five healthy controls completed the study. On day zero, a biopsy of the vastus lateralis was taken. On day eight, participants completed a standardized eccentric knee extension exercise protocol of the biopsied leg on an isokinetic device. 24 hours later, on day nine, a second biopsy was taken in the same muscle. Proteomics were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS): all samples were pooled to create an ion library which was used to assess muscle protein expression in individual samples. A total of 894 proteins were identified. Protein expression and its modulation by exercise were heterogenous in DM1 individuals. The expression of 111 proteins was significantly modulated by exercise for the control subjects while 50 were significantly modulated in DM1 subjects. Of these proteins, 9 had increased their expression in both groups. This includes 4 structural proteins (FLNC, NEXN, XIRP1 and NRAP), 2 translation factors (EF2 and IF5), a ubiquitin and skeletal muscle differentiation modulator (KLHL40), a chaperone protein (HS90B) and a neutrophil serine protease inhibitor (ILEU). In both groups, a mitochondrial protein (NDUB8) had decreased its expression. Further analyses are being conducted to assess how DM1 individuals responded differently to exercise compared to healthy controls. In conclusion, despite the genetic default, DM1 muscle has some similar responses to exercise compared to healthy controls although it remains heterogenous among DM1 individuals.

Differential Effects Of Exercise Induced Muscle Damage On Multiple Noxious Stimuli

Many clinical musculoskeletal pain conditions are characterized by chronic inflammation. Inflammation leads to the release of inflammatory cytokines that activate or sensitizes nociceptors leading to pain sensitivity. An unresolved issue is whether inflammation affects all nociceptors in a similar manner. Exercise induced muscle damage in the days following a bout of eccentric exercise has been proposed as a valid model of simulating clinical inflammatory pain to be used in healthy samples. PURPOSE: We sought to induce localized inflammation using eccentric exercise to test various painful stimuli (pressure, thermal, and electrical) regarding an individual’s pain sensitivity in a limb that was eccentrically exercised versus a limb that was not exercised. METHODS: 18 healthy participants (9F, age: 24.6 ± 3.3) completed baseline pressure pain thresholds (PPT), thermal pain threshold (TPT), and nociceptive flexion reflex (NFR) in both legs and again 48 hours after a muscle damaging protocol. The participants performed a minimum of 6 rounds of 10 eccentric leg extension exercises to induce muscle damage and localized inflammation in the right quadriceps only. RESULTS: Significant main effect of time for PPT (%diff; -58.9 ± 23.1; p = 0.02, ηp2 = 0.28) but no main effect was observed for limb (%diff; -15.5 ± 23.9; p = 0.53, ηp2 = 0.02). In contrast there was a significant interaction between time and limb (p < 0.001, ηp2 = 0.47) whereby post hoc correction revealed participants had lower PPT’s in the right leg only after the damage protocol (%diff; -105.9 ± 29.2; p = 0.002). No main effects or interactions were observed for TPT and NFR. CONCLUSION: Those with chronic inflammatory pain usually have an increased sensitivity to pressure, thermal, and electrical stimuli whereas our sample with acute inflammation only had sensitivity to mechanical pain. Exercise induced inflammation may reflect a peripheral sensitivity localized to the damage muscle rather than a global sensitivity that those with chronic pain display.

Well-Trained Elders Have Antioxidant Responses and an Equal Magnitude of EIMD as Young Adults

Aim The aim of the study was to investigate acute and chronic effects of a two-week eccentric concentric, dynamometric training concerning the time-course changes of blood antioxidant parameters (total antioxidant capacity, catalase enzyme activity, thiol concentration), and to compare the adaptability of young and older muscle to this type of training. Methods Seventeen moderately trained young and older men participated in this research. Subjects performed six eccentric concentric exercise bouts during the training period and maximal voluntary isometric contraction torque, plasma CK and intensity of muscle soreness were determined before and 24 h after the first exercise. During five testing sessions (baseline, 24 h, 48 h, week 1, week 2) the level of blood antioxidants were measured. Results No significant changes were registered in total antioxidant capacity and catalase enzyme activity for any time points; furthermore, no difference was found between groups during the training period. However, total thiol concentrations measured two weeks after the first exercise bout significantly differed between the young and elderly groups. Plasma CK and the subjective intensity of soreness elevated significantly 24 h following the first training, while maximal voluntary isometric contraction torque decreased at the same time. Conclusions Our results do not support previous findings that chronic, short-term eccentric concentric training programs enhance the antioxidant defense of well-trained older and young men. This type and setting of exercise did not cause a different time course of changes in the markers of exercise-induced muscle damage (EIMD) in the studied population. Subjects may already have adapted to maintain constant levels of antioxidants and isometric torque due to their active lifestyle.

Changes in Insulin Sensitivity and Lipid Profile Markers Following Initial and Secondary Bouts of Multiple Eccentric Exercises.

An acute bout of eccentric exercise affects insulin sensitivity and lipid profile, but how the magnitude of muscle damage affects them is not clear. We compared changes in blood insulin sensitivity and lipid markers after the first (EC1) and second (EC2) eccentric exercise bouts. Fifteen sedentary young men performed arm, leg and trunk muscle eccentric exercises, and repeated them 2 weeks later. Fasting blood samples were taken before, 2 h and 1–5 days after each exercise bout to analyze plasma creatine kinase (CK) activity, serum glucose (GLU), insulin, homeostasis model assessment (HOMA), triacylglycerols (TG), total (TC) and low- (LDLC) and high-density lipoprotein cholesterol (HDLC) concentrations as well as TC/HDLC ratio. Changes in these measures were compared between bouts and relationships to peak plasma CK activity were analyzed. Plasma CK activity increased (p < 0.05) after EC1 (peak: 101,668 ± 58,955 IU/L) but not after EC2. The magnitude of changes in GLU (peak after EC1: 26 ± 10% vs. EC2: 7 ± 6%), insulin (46 ± 27% vs. 15 ± 8%), HOMA (86 ± 48% vs. 24 ± 15%), TC (−20 ± 5% vs. −6 ± 4%), TG (−32 ± 11% vs. −6 ± 3%), LDHC (−47 ± 15% vs. −12 ± 9%), HDLC (35 ± 26% vs. 7 ± 4%), and TC/HDLC ratio (−139 ± 13% vs. −11 ± 7%) were significantly greater after EC1 than EC2. Peak plasma CK activity was significantly (p < 0.05) correlated with the peak changes in blood insulin sensitivity and lipid markers for the combined data of EC1 and EC2. These results suggest that the greater the magnitude of muscle damage, the greater the magnitude of changes in the insulin sensitivity to a negative direction and lipid markers to a positive direction.

The Food Nutrient Index and Inflammation Are Not Linked to Eccentric Exercise-Induced Muscle Damage

ObjectivesVariation in muscle damage following eccentric exercise is wide-ranging and largely unexplained. This study investigated linkages between eccentric exercise-induced increases in the muscle damage biomarker creatine kinase (CK) and diet quality, body composition and fitness test performance, diagnostic chemistries, oxidative stress, and inflammation.MethodsParticipants included 53 healthy, non-obese male (n = 30) and female adults (n = 23) (20–55 y, BMI < 30 kg/m2) who were not engaged in regular resistance training. After familiarization, participants engaged in a 90-min bout of whole-body eccentric exercise (90-EE) (17 exercises). Changes in muscle soreness (DOMS, 1–10 scale) and damage biomarkers (serum CK, myoglobin), exercise performance, oxidative stress (4-hydroxynonenal or 4HNE), inflammation (CRP, IL-18, IL-16, IL-10), serum cortisol, and diagnostic chemistries were monitored immediately post-90-EE, and then each morning during a 4-d recovery period. Blood samples were collected in an overnight fasted state, with serum CK, myoglobin, cortisol, and diagnostic chemistries measured at a clinical lab. IL-18, IL-6, IL-10, and 4HNE were assayed by ELISA. Participants entered food and beverage intake in 3-d food records with nutrient and flavonoid intake assessed and the Food Nutrient Index (FNI) calculated using eight under-consumed nutrients.ResultsThe 90-EE bout induced significant DOMS and muscle damage, inflammation and oxidative stress, and decreases in strength and anaerobic power. CK increased throughout the 4-d recovery period, with the highest levels measured on the 4th day (range, 60–17,040 U/L; mean ± SD, 1,565 ± 3,132 U/L). CK was correlated with other tissue damage biomarkers including aspartate aminotransferase (r = 0.946), lactate dehydrogenase (r = 0.884), and myoglobin (r = 0.763). Under linear regression analysis with non-tissue damage outcomes including FNI (68.7 ± 15.7), DOMS and serum cortisol emerged as the best predictors of post-90-EE CK variance [R2 = 0.367, F(2,50) = 14.48, p < 0.001].ConclusionsThe CK response to 90-EE varied widely between participants with 37% of the variance related to perceptions of muscle soreness and the stress hormone cortisol, but not diet quality, inflammation, oxidative stress, or fitness test performance.Funding SourcesMegaFood.

Influence of Almond Supplementation on Recovery Responses to Unaccustomed Exercise in Untrained Adults

ObjectivesThis study with untrained adults determined if 4-weeks supplementation with almonds compared to a matched calorie, common snack (cereal bars) had an influence on exercise performance, muscle soreness and damage, and mood states during a 4-d period after engaging in an acute, 90-min bout of eccentric exercise (90-EE).MethodsParticipants included 64 healthy, non-obese male and female adults (30–65 years, BMI 23–30 kg/m2) who were not engaged in regular resistance training. Participants were randomized to almond (57 g/d) (AL) and cereal bar (324 kcal/d) (CB) groups for 4 weeks prior to engaging in 90-EE (17 exercises). Changes in muscle soreness and damage biomarkers, exercise performance tests, and mood states were monitored before and after the 4-week supplementation period, immediately post-90-EE, and then each morning during a 4-d recovery period.ResultsThe 90-EE caused significant delayed onset of muscle soreness that peaked 1–2-d post-exercise with no group differences (time, p < 0.001, interaction, p = 0.187). Serum muscle damage biomarkers increased strongly in both groups but were significantly lower in AL vs. CB immediately post-90-EE (creatine kinase, p = 0.034, myoglobin, p = 0.036) and after 1-d recovery (creatine kinase, p = 0.013). Several measures of performance were negatively affected by 90-EE including the 60-yard shuttle run time, leg-back strength, bench press repetitions, and peak- and mean-power during the 30-sec Wingate test (all p < 0.01). AL vs. CB had higher levels of leg-back strength during recovery (interaction, p = 0.029), but the groups did not differ in other performance measures. Total mood disturbance (TMD) and fatigue increased post-90-EE, but the magnitude of these changes tended to be lower in AL vs. CB (interaction, p = 0.130, p = 0.051, respectively). Vigor was higher immediately post-90-EE in AL vs. CB (p = 0.060).ConclusionsThe 90-EE protocol induced significant muscle damage, muscle soreness, reduced strength and power performance, and mood disturbance. AL vs. CB ingestion (4 weeks) was linked to reduced serum levels of muscle damage, higher levels of leg/back strength, and a lower magnitude of mood disturbance. Thus, chronic almond ingestion may help mitigate negative physiological and mental responses to unaccustomed exercise by untrained individuals.Funding SourcesAlmond Board of California.

Consumption of a Soy Snack Bite After Resistance Exercise: Impact on Recovery in Athletes

ObjectivesTo assess the effectiveness of a novel soy pretzel (NSP) in mitigating symptoms of exercise induced muscle damage (EIMD). Due to the high levels of protein and isoflavones found in soy, it is hypothesized that consumption of NSP after exercise will reduce muscle soreness and inflammation.MethodsTen male subjects between the ages 18–30 completed a double-blind crossover study and were randomly assigned to consume either the study agent or placebo. The exercise protocol involved repeated bouts of eccentric exercise in the form of a squat. 6 sets of 10 repetition squats at 70% 1 repetition maximum was selected to induce muscle damage. Blood was collected pre- and post-exercise in an effort to capture the peaks of various biomarkers. Urine was collected for 24 hours starting immediately after exercise to assess urinary isoflavone content. Muscle soreness was assessed using a visual analog scale. Sensory acceptability scores were collected using a 9-point hedonic scale.ResultsBoth pretzels had high acceptability scores of 7 out of 9. Testosterone was significantly blunted in the serum following soy (418.96 ± 146.21) compared to wheat (471.31 ± 166.07), indicating increased uptake by the muscle due to protein and essential amino acids found in NSP (p = 0.0072). Creatine Kinase and myoglobin peaked higher in soy than wheat, however, attenuated faster in the treatment arm. The same pattern was observed for proinflammatory cytokines IL-6 and TNF-a. IL-6, while significantly higher in soy, attenuated faster starting at the 6-hour time point. Isoflavones peak in the blood 6 hours after consumption, suggesting they may be responsible for the rapid decline following soy consumption. Urinary isoflavones daidzein, genestein, glycitein were all significantly elevated (p < 0.001, 0.011 and 0.011 respectively) following soy consumption as were ODMA and formononetin, indicating that a one-time dose of soy, is sufficient to elevate urinary excretion.ConclusionsSignificantly lower levels of serum testosterone and more rapid decreases in biomarkers of inflammation and muscle damage provide support for the use of NSP in an acute setting to mitigate symptoms of EIMD. Additionally, the soy pretzel received high sensory acceptability scores among the target population, which is promising for future commercialization.Funding SourcesThe Ohio Soybean Council.

The Effect of Capacitive and Resistive Electric Transfer Intervention on Delayed-Onset Muscle Soreness Induced by Eccentric Exercise.

This study aimed to investigate the acute effect of capacitive and resistive electric transfer (CRet) intervention on eccentrically damaged muscle. A total of 28 healthy and sedentary male volunteers were randomly allocated to either CRet intervention or control groups. The participants performed a bout of eccentric exercise of the knee extensors with the dominant leg and received 30 min of CRet intervention of the quadriceps 48 h after the exercise. The dependent variables for the analysis were knee flexion range of motion (ROM), muscle soreness and maximum voluntary isometric (MVC-ISO), and concentric contraction (MVC-CON) torque of the knee extensors. These were measured prior to exercise (baseline) and before and after CRet intervention (48 h after the exercise). The results showed that knee flexion ROM, muscle strength (MVC-ISO and MVC-CON), and muscle soreness significantly improved after CRet intervention. CRet intervention may improve muscle soreness and loss of muscle function in an eccentrically damaged muscle.

Acute Left Atrial Response to Different Eccentric Resistance Exercise Loads in Patients with Heart Failure with Middle Range Ejection Fraction: A Pilot Study.

In this study, we aimed to assess acute changes occurring on atrial function following single bouts of eccentric resistance exercise (ECC-RE) performed at two different loads. Twenty-five patients with chronic heart failure with middle range ejection fraction (HFmrEF) participated in three experimental sessions in a randomized order and on separate days: two sessions of ECC RE at 20% (ECC-20) of one-repetition maximum (1-RM) and 50% (ECC-50) 1-RM, and one session of control, without exercise. Each session lasted three minutes. Before and immediately after the sessions, patients underwent echocardiography and blood pressure and heart rate measurement. Peak atrial longitudinal strain (PALS) and peak atrial contractile strain (PACS) significantly increased after both ECC-20 (+16.3%) and ECC-50 (+18.1%) compared to control (between sessions p = 0.022). Peak atrial contractile strain (PACS) significantly increased after ECC-50 (+28.4%) compared to ECC-20 (+17.0%) and control (between sessions p = 0.034). The ratio of transmitral and annular velocities (E/E’) increased significantly after ECC-20 (+10.4%) and ECC-50 (+19.0%) compared to control (between groups p = 0.003). EF, left ventricular longitudinal strain, and stroke volume did not change after ECC-RE sessions compared to control. Cardiac output increased significantly after ECC-20 and ECC-50 compared to control, (between groups p = 0.025). In conclusion, both ECC-RE sessions were well tolerated, and LA functional reserve was properly mobilized in response to ECC-RE in patients with HFmrEF. Cardiac output increased at the cost of an increased LV filling pressure, but no detrimental changes of LV function occurred.

Nestin and osteocrin mRNA increases in human semitendinosus myotendinous junction 7days after a single bout of eccentric exercise.

The myotendinous junction (MTJ), a specialized interface for force transmission between muscle and tendon, has a unique transcriptional activity and is highly susceptible to muscle strain injury. Eccentric exercise training is known to reduce this risk of injury, but knowledge of the influence of exercise on the MTJ at the molecular and cellular levels is limited. In this study, 30 subjects were randomized to a single bout of eccentric exercise 1week prior to tissue sampling (exercised) or no exercise (control). Samples were collected from the semitendinosus as part of reconstruction of the anterior cruciate ligament and divided into fractions containing muscle, MTJ and tendon, respectively. The concentrations of macrophages and satellite cells were counted, and the expression of genes previously known to be active at the MTJ were analyzed by real-time-quantitative PCR. An effect of the single bout of exercise was found on the expression of nestin (NES) and osteocrin (OSTN) mRNA in the MTJ and tendon fractions. Genes earlier identified at the MTJ (COL22A1, POSTN, ADAMTS8, MNS1, NCAM1) were confirmed to be expressed at a significantly higher level in the MTJ compared to muscle and tendon but were unaffected by exercise. In the exercise group a higher concentration of macrophages, but not of satellite cells, was seen in muscle close to the MTJ. The expression of NES and OSTN was higher in human semitendinosus MTJ 1week after a single session of heavy eccentric exercise. Based on these results, NES and OSTN could have a part in explaining how the MTJ adapts to eccentric exercise.