Effect of exercise-induced muscle damage on vascular function and skeletal muscle microvascular deoxygenation

Jaboticaba berry (Myrciaria jaboticaba) supplementation protects against micro- and macrovascular dysfunction induced by eccentric exercise: a randomized clinical trial

Physical activities that are unaccustomed and involve eccentric muscle contractions have been demonstrated to temporarily impair macrovascular and microvascular functions, which may be caused by exercise-induced oxidative stress. Jaboticaba (Myrciaria jaboticaba) is a famous Brazilian berry that has been described to exhibit high antioxidant activity. However, no human study has investigated the protective effects of jaboticaba consumption against the vascular damage induced by eccentric exercise. Therefore, the present study aimed to assess whether supplementation with jaboticaba berry juice could positively affect macro- and microvascular functions within 48 hours after eccentric exercise. This randomized, double-blind, placebo-controlled, parallel trial enrolled 24 healthy participants consuming 250 mL per day of jaboticaba berry juice (containing ∼1,300 mg of total polyphenols) or placebo for 6 days. At the baseline, pre-exercise, and 24 h and 48 h postexercise stages, blood samples were taken for analysis of reduced glutathione (GSH) levels. Also, brachial artery flow-mediated dilation (FMD), blood flow, and tissue oxygen saturation (StO2) responses to 5-minute cuff occlusion were assessed using Doppler ultrasound and near-infrared spectroscopy, respectively. Our findings revealed significant decreases in blood GSH (P < 0.001, ES = 0.76), FMD (P = 0.005, ES = 0.48), reperfusion slope of StO2 (P = 0.018, ES = 0.42) at 24 h and blood flow (P = 0.012, ES = 0.42) at 48 h following eccentric exercise in the control group as compared to the jaboticaba berry juice group. Our results demonstrated that jaboticaba berry juice prevented the exercise-induced increase in reactive oxygen species production and protected macro- and microvascular functions against the damage caused by eccentric exercise, suggesting that jaboticaba berry consumption could protect the vascular function under conditions of imbalance in redox homeostasis.

The Impact of Exercise-Induced Muscle Damage on Various Cycling Performance Metrics: A Systematic Review and Meta-Analysis

ABSTRACT

Devantier-Thomas, B, Deakin, GB, Crowther, F, Schumann, M, and Doma, K. The impact of exercise-induced muscle damage on various cycling performance metrics: a systematic review and meta-analysis. J Strength Cond Res 38(1): 196-212, 2024-This systematic review and meta-analysis examined the impact of exercise-induced muscle damage (EIMD) on cycling performance. The primary outcome measure was cycling performance, whereas secondary outcome measures included creatine kinase (CK), delayed-onset muscle soreness (DOMS), and muscular contractions. Data were extracted and quantified through forest plots to report on the standardized mean difference and p values. The meta-analysis showed no significant change in oxygen consumption at 24-48 hours (p > 0.05) after the muscle damage protocol, although ventilation and rating of perceived exertion significantly increased (p < 0.05) during submaximal cycling protocols. Peak power output during both sprint and incremental cycling performance was significantly reduced (p < 0.05), but time-trial and distance-trial performance showed no change (p > 0.05). Measures of CK and DOMS were significantly increased (p < 0.05), whereas muscular force was significantly reduced following the muscle-damaging protocols (p < 0.05), confirming that cycling performance was assessed during periods of EIMD. This systematic review showed that EIMD affected both maximal and submaximal cycling performance. Therefore, coaches should consider the effect of EIMD on cycling performance when implementing unaccustomed exercise into a cycling program. Careful consideration should be taken to ensure that additional training does not impair performance and endurance adaptation.

The relationship between hemoglobin and [Formula: see text]: A systematic review and meta-analysis

OBJECTIVE

There is widespread agreement about the key role of hemoglobin for oxygen transport. Both observational and interventional studies have examined the relationship between hemoglobin levels and maximal oxygen uptake ([Formula: see text]) in humans. However, there exists considerable variability in the scientific literature regarding the potential relationship between hemoglobin and [Formula: see text]. Thus, we aimed to provide a comprehensive analysis of the diverse literature and examine the relationship between hemoglobin levels (hemoglobin concentration and mass) and [Formula: see text] (absolute and relative [Formula: see text]) among both observational and interventional studies.

METHODS

A systematic search was performed on December 6th, 2021. The study procedures and reporting of findings followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Article selection and data abstraction were performed in duplicate by two independent reviewers. Primary outcomes were hemoglobin levels and [Formula: see text] values (absolute and relative). For observational studies, meta-regression models were performed to examine the relationship between hemoglobin levels and [Formula: see text] values. For interventional studies, meta-analysis models were performed to determine the change in [Formula: see text] values (standard paired difference) associated with interventions designed to modify hemoglobin levels or [Formula: see text]. Meta-regression models were then performed to determine the relationship between a change in hemoglobin levels and the change in [Formula: see text] values.

RESULTS

Data from 384 studies (226 observational studies and 158 interventional studies) were examined. For observational data, there was a positive association between absolute [Formula: see text] and hemoglobin levels (hemoglobin concentration, hemoglobin mass, and hematocrit (P<0.001 for all)). Prespecified subgroup analyses demonstrated no apparent sex-related differences among these relationships. For interventional data, there was a positive association between the change of absolute [Formula: see text] (standard paired difference) and the change in hemoglobin levels (hemoglobin concentration (P<0.0001) and hemoglobin mass (P = 0.006)).

CONCLUSION

These findings suggest that [Formula: see text] values are closely associated with hemoglobin levels among both observational and interventional studies. Although our findings suggest a lack of sex differences in these relationships, there were limited studies incorporating females or stratifying results by biological sex.

Preexercise intermittent passive stretching and vascular function after treadmill exercise

Acute aerobic exercise stress is associated with decreased endothelial function that may increase the likelihood of an acute cardiovascular event. Passive stretch (PS) elicits improvements in vascular function, but whether PS can be performed before exercise to prevent declines in vascular function remains unknown. This strategy could be directly applicable in populations that may not be able to perform dynamic exercise. We hypothesized that preexercise PS would provide better vascular resilience after treadmill exercise. Sixteen healthy college-aged males and females participated in a single laboratory visit and underwent testing to assess micro- and macrovascular function. Participants were randomized into either PS group or sham control group. Intermittent calf PS was performed by having the foot in a splinting device for a 5-min stretch and 5-min relaxation, repeated four times. Then, a staged V̇o2 peak test was performed and 65% V̇o2 peak calculated for subjects to run at for 30 min. Near-infrared spectroscopy-derived microvascular responsiveness was preserved with the PS group [(pre: 0.53 ± 0.009%/s) (post: 0.56 ± 0.012%/s; P = 0.55)]. However, there was a significant reduction in the sham control group [(pre: 0.67 ± 0.010%/s) (post: 0.51 ± 0.007%/s; P = 0.05)] after treadmill exercise. Flow-mediated vasodilation (FMD) of the popliteal artery showed similar responses. In the PS group, FMD [(pre: 7.23 ± 0.74%) (post: 5.86 ± 1.01%; P = 0.27)] did not significantly decline after exercise. In the sham control group, FMD [(pre: 8.69 ± 0.72%) (post: 5.24 ± 1.24%; P < 0.001)] was significantly reduced after treadmill exercise. Vascular function may be more resilient if intermittent PS is performed before moderate-intensity exercise and, importantly, can be performed by most individuals.NEW & NOTEWORTHY We demonstrate for the first time that popliteal artery and gastrocnemius microvascular responsiveness after acute aerobic exercise are reduced. The decline in vascular function was mitigated in those who performed intermittent passive stretching before the exercise bouts. Collectively, these findings suggest that intermittent passive stretching is a novel method to increase vascular resiliency before aerobic activity.

Eccentric exercise 24 h prior to hypobaric decompression increases decompression strain

PURPOSE

Animal studies have shown that recent musculoskeletal injuries increase the risk of decompression sickness (DCS). However, to date no similar experimental study has been performed in humans. The aim was to investigate if exercise-induced muscle damage (EIMD)-as provoked by eccentric work and characterized by reduced strength and delayed-onset muscle soreness (DOMS)-leads to increased formation of venous gas emboli (VGE) during subsequent hypobaric exposure.

METHODS

Each subject (n = 13) was on two occasions exposed to a simulated altitude of 24,000 ft for 90 min, whilst breathing oxygen. Twenty-four hours prior to one of the altitude exposures, each subject performed 15 min of eccentric arm-crank exercise. Markers of EIMD were reduction in isometric m. biceps brachii strength and DOMS as assessed on the Borg CR10 pain scale. The presence of VGE was measured in the right cardiac ventricle using ultrasound, with measurements performed at rest and after three leg kicks and three arm flexions. The degree of VGE was evaluated using the six-graded Eftedal-Brubakk scale and the Kisman integrated severity score (KISS).

RESULTS

Eccentric exercise induced DOMS (median 6.5), reduced the biceps brachii strength (from 230 ± 62 N to 151 ± 8.8 N) and increased the mean KISS at 24,000 ft, both at rest (from 1.2 ± 2.3 to 6.9 ± 9.2, p = 0.01) and after arm flexions (from 3.8 ± 6.2 to 15.5 ± 17.3, p = 0.029).

CONCLUSION

EIMD, induced by eccentric work, provokes release of VGE in response to acute decompression.

Branched-Chain Amino Acids Supplementation Does Not Accelerate Recovery after a Change of Direction Sprinting Exercise Protocol

BCAAs supplementation has been widely used for post-exercise recovery. However, no evidence is currently available to answer the question of whether BCAAs supplementation can attenuate muscle damage and ameliorate recovery after a bout of change of direction (COD) sprinting, which is an exercise motion frequently used during team sport actions. This study aimed to assess the effect of BCAAs supplementation on muscle damage markers, subjective muscle soreness, neuromuscular performance, and the vascular health of collegiate basketball players during a 72 h recovery period after a standardized COD protocol. Participants orally received either BCAAs (0.17 g/kg BCAAs + 0.17 g/kg glucose) or placebo (0.34 g/kg glucose) supplementation before and immediately after a COD exercise protocol in a randomized, crossover, double-blind, and placebo-controlled manner. Creatine kinase increased immediately after exercise and peaked at 24 h, muscle soreness remained elevated until 72 h, whilst arterial stiffness decreased after exercise for both supplemented conditions. A negligibly lower level of interleukin-6 was found in the BCAAs supplemented condition. In conclusion, the results of this study do not support the benefits of BCAAs supplementation on mitigating muscle damage and soreness, neuromuscular performance, and arterial stiffness after COD for basketball players.

Effects of nociceptive and mechanosensitive afferents sensitization on central and peripheral hemodynamics following exercise-induced muscle damage

This study aims to test the separated and combined effects of mechanoreflex activation and nociception through exercise-induced muscle damage (EIMD) on central and peripheral hemodynamics before and during single passive leg movement (sPLM). Eight healthy young males undertook four experimental sessions, in which a sPLM was performed on the dominant limb while in each specific session the contralateral was: 1) in a resting condition (CTRL), 2) stretched (ST), 3) resting after EIMD called delayed onset muscle soreness (DOMS) condition, or 4) stretched after EIMD (DOMS + ST). EIMD was used to induce DOMS in the following 24-48 h. Femoral blood flow (FBF) was assessed using Doppler ultrasound whereas central hemodynamics were assessed via finger photoplethysmography. Leg vascular conductance (LVC) was calculated as FBF/mean arterial pressure (MAP). RR-intervals were analyzed in the time (root mean squared of successive intervals; RMSSD) and frequency domain [low frequency (LF)/high frequency (HF)]. Blood samples were collected before each condition and gene expression analysis showed increased fold changes for P2X4 and IL1β in DOMS and DOMS + ST compared with baseline. Resting FBF and LVC were decreased only in the DOMS + ST condition (-26 mL/min and -50 mL/mmHg/min respectively) with decreased RMSSD and increased LF/HF ratio. MAP, HR, CO, and SV were increased in ST and DOMS + ST compared with CTRL. Marked decreases of Δpeaks and AUC were observed for FBF (Δ: -146 mL/min and -265 mL respectively) and LVC (Δ: -8.66 mL/mmHg/min and ±1.7 mL/mmHg/min respectively) all P < 0.05. These results suggest that the combination of mechanoreflex and nociception resulted in decreased vagal tone and concomitant rise in sympathetic drive that led to increases in resting central hemodynamics with reduced limb blood flow before and during sPLM.NEW & NOTEWORTHY Exercise-induced muscle damage (EIMD) is a well-known model to study mechanical hyperalgesia and muscle peripheral nerve sensitizations. The combination of static stretching protocol on the damaged limb extensively increases resting central hemodynamics with reduction in resting limb blood flow and passive leg movement-induced hyperemia. The mechanism underlining these results may be linked to reduction of vagal tone with concomitant increase in sympathetic activity following mechano- and nociceptive activation.

Effect of heat pre-conditioning on recovery following exercise-induced muscle damage

This study investigated the influence of heat pre-conditioning on the recovery of muscle torque, microvascular function, movement economy and stride mechanics following exercise-induced muscle damage (EIMD). Twenty male participants were equally assigned to a control (CON) and an experimental group (HEAT), and performed a 30-min downhill run (DHR) to elicit EIMD. HEAT group received three consecutive days of heat exposure (45.1 ​± ​3.2 ​min of hot water immersion at 42 ​°C) prior to DHR. Microvascular function (near-infrared spectroscopy), maximal voluntary contraction (MVC) torque of the knee extensors, as well as two treadmill-based steady-state runs performed below (SSR-1) and above (SSR-2) the first ventilatory threshold were assessed prior to DHR and repeated for four consecutive days post-DHR (D1-POST to D4-POST). The decline in MVC torque following EIMD was attenuated in HEAT compared with CON at D1-POST (p ​= ​0.037), D3-POST (p ​= ​0.002) and D4-POST (p ​= ​0.022). Muscle soreness increased in both CON and HEAT, but was significantly attenuated in HEAT compared with CON at D2-POST (p ​= ​0.024) and D3-POST (p ​= ​0.013). Microvascular function decreased in CON from D1-POST to D3-POST (p ​= ​0.009 to 0.018), and was lower compared with HEAT throughout D1-POST to D3-POST (p ​= ​0.003 to 0.017). Pre-heat treatment decreased the magnitude of strength loss and muscle soreness, as well as attenuated the decline in microvascular function following EIMD. Heat treatment appears a promising pre-conditioning strategy when embarking on intensified training periods or competition.

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Three days of heat pre-conditioning decreases the extent of strength loss, soreness and microvascular function after EIMD.

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Pre heat treatment might be a promising preconditioning tool prior to intensified training periods or competition.

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Heat tretament may positively impact activities of daily living, training quality and adherence to training programs.

Downhill Running: What Are The Effects and How Can We Adapt? A Narrative Review

Downhill running (DR) is a whole-body exercise model that is used to investigate the physiological consequences of eccentric muscle actions and/or exercise-induced muscle damage (EIMD). In a sporting context, DR sections can be part of running disciplines (off-road and road running) and can accentuate EIMD, leading to a reduction in performance. The purpose of this narrative review is to: (1) better inform on the acute and delayed physiological effects of DR; (2) identify and discuss, using a comprehensive approach, the DR characteristics that affect the physiological responses to DR and their potential interactions; (3) provide the current state of evidence on preventive and in-situ strategies to better adapt to DR. Key findings of this review show that DR may have an impact on exercise performance by altering muscle structure and function due to EIMD. In the majority of studies, EIMD are assessed through isometric maximal voluntary contraction, blood creatine kinase and delayed onset muscle soreness, with DR characteristics (slope, exercise duration, and running speed) acting as the main influencing factors. In previous studies, the median (25th percentile, Q1; 75th percentile, Q3) slope, exercise duration, and running speed were - 12% (- 15%; - 10%), 40 min (30 min; 45 min) and 11.3 km h-1 (9.8 km h-1; 12.9 km h-1), respectively. Regardless of DR characteristics, people the least accustomed to DR generally experienced the most EIMD. There is growing evidence to suggest that preventive strategies that consist of prior exposure to DR are the most effective to better tolerate DR. The effectiveness of in-situ strategies such as lower limb compression garments and specific footwear remains to be confirmed. Our review finally highlights important discrepancies between studies in the assessment of EIMD, DR protocols and populations, which prevent drawing firm conclusions on factors that most influence the response to DR, and adaptive strategies to DR.

Relationships between resting blood flow and the indices of muscle damage after eccentric contractions

PURPOSE

The aim of the study is to examine the relationships between increments in resting blood flow and isometric maximal voluntary contraction (MVC) force reduction, muscle soreness, and swelling after eccentric contractions (ECs).

METHODS

Twenty-one young healthy men (age 20.8 ± 1.6 years; height 172.0 ± 5.3 cm; weight 64.9 ± 7.7 kg) were recruited for this study. All participants performed right arm ECs in five sets of 20 repetitions with 3 min of rest between the sets. The dumbbell weight corresponded to 60% MVC force of isometric contraction of elbow flexors with 90° elbow joint angle. Resting forearm blood flow (FBF), the MVC force, the muscle thickness (MT), and muscle soreness of elbow flexors, heart rate (HR), and blood pressure (BP) of brachial artery were measured before, 24 and 48 h after ECs.

RESULTS

Average and peak resting FBF after ECs significantly changed from the average values before ECs (21% and 39% increase, respectively, P < 0.01). However, resting HR and BP were not significantly different after ECs. Average increase in resting FBF showed a significant relationship with average isometric MVC force reduction (r =  - 0.45, P < 0.05), peak isometric MVC force reduction (r =  - 0.48, P < 0.05), average muscle soreness (r = 0.49, P < 0.05), and peak muscle soreness (r = 0.49, P < 0.05). Moreover, stepwise multiple regression analysis revealed that average increased resting FBF was explained by isometric MVC force reduction and muscle soreness (adjusted R² = 0.33).

CONCLUSIONS

These results suggested that increments in resting blood flow reflect muscle damage, and increased resting blood flow may be a result of acute inflammatory response induced by muscle damage.

Impaired microvascular reactivity after eccentric muscle contractions is not restored by acute ingestion of antioxidants or dietary nitrate

Unaccustomed eccentric exercise leads to impaired microvascular function but the underlying mechanism is unknown. In this study, we evaluated the role of oxidative stress and of nitric oxide (NO) bioavailability. Thirty young men and women performed eccentric contractions of the tibialis anterior (TA) muscle (ECC), with the contralateral leg serving as nonexercising control (CON). Participants were randomized into three groups ingesting an antioxidant cocktail (AO), beetroot juice (BR) or placebo 46 h postexercise. At baseline and 48 h postexercise, hyperemic responses to brief muscle contractions and 5 min of cuff occlusion were assessed bilaterally in the TA muscles using blood oxygen level dependent (BOLD) magnetic resonance imaging. Eccentric contractions resulted in delayed time-to-peak (~22%; P < 0.001), blunted peak (~21%; P < 0.001) and prolonged time-to-half relaxation (~12%, P < 0.001) in the BOLD response to brief contractions, with no effects of AO or BR, and no changes in CON. Postocclusive time-to-peak was also delayed (~54%; P < 0.001) in ECC, with no effects of AO or BR, and no changes in CON. Impaired microvascular reactivity after eccentric contractions is confined to the exercised tissue, and is not restored with acute ingestion of AO or BR. Impairments in microvascular reactivity after unaccustomed eccentric contractions may result from structural changes within the microvasculature that can diminish muscle blood flow regulation during intermittent activities requiring prompt adjustments in oxygen delivery.

Characterization of surface electromyography signals of biceps brachii muscle in fatigue using symbolic motif features

Exercise-induced muscle damage is a condition which results in the loss of muscle function due to overexertion. Muscle fatigue is a precursor of this phenomenon. The characterization of muscle fatigue plays a crucial role in preventing muscle damage. In this work, an attempt is made to develop signal processing methods to understand the dynamics of the muscle’s electrical properties. Surface electromyography signals are recorded from 50 healthy adult volunteers under dynamic curl exercise. The signals are preprocessed, and the first difference signal is computed. Furthermore, ascending and descending slopes are used to generate a binary sequence. The binary sequence of various motif lengths is analyzed using features such as the average symbolic occurrence, modified Shannon entropy, chi-square value, time irreversibility, maximum probability of pattern and forbidden pattern ratio. The progression of muscle fatigue is assessed using trend analysis techniques. The motif length is optimized to maximize the rho value of features. In addition, the first and the last zones of the signal are compared with standard statistical tests. The results indicate that the recorded signals differ in both frequency and amplitude in both inter- and intra-subjects along the period of the experiment. The binary sequence generated has information related to the complexity of the signal. The presence of more repetitive patterns across the motif lengths in the case of fatigue indicates that the signal has lower complexity. In most cases, larger motif length resulted in better rho values. In a comparison of the first and the last zones, most of the extracted features are statistically significant with p < 0.05. It is observed that at the motif length of 13 all the extracted features are significant. This analysis method can be extended to diagnose other neuromuscular conditions.

Decreased running economy is not associated with decreased force production capacity following downhill running in untrained, young men

The present study investigated the relationships between changes in running economy (RE) and indirect muscle damage markers following downhill running (DHR) to test the hypothesis that decreased RE after DHR would be associated with decreases in muscle function. Forty-five young men ran downhill (-15%) for 30 min at the velocity corresponding to 70% of their peak oxygen uptake (VO₂peak). Oxygen uptake (VO₂) and other parameters possibly associated with RE (blood lactate concentration, perceived exertion, stride length and frequency) were measured during 5-minute level running at the velocity corresponding to 80%VO₂peak before, immediately after and 1-3 days after DHR. Knee extensor maximal voluntary contraction torque (MVC), rate of torque development, vertical jump performance, muscle soreness and serum creatine kinase activity were assessed at the same time points. The values of the dependent variables were compared among time points by one-way ANOVAs followed by Bonferroni post-hoc tests when appropriate. Pearson's correlation tests were used to examine relationships between changes in VO₂ (RE parameter) and changes in muscle damage parameters. VO₂ during the level run increased (p < 0.05) immediately after DHR (18.3 ± 4.6%) and sustained until 2 days post-DHR (11.7 ± 4.2%). MVC decreased (p < 0.05) immediately (-21.8 ± 6.1%) to 3 days (-13.6 ± 5.9%) post-DHR, and muscle soreness developed 1-3 days post-DHR. The magnitude of changes in VO₂ did not significantly (p < 0.05) correlate with the changes in muscle damage makers (r = -0.02-0.13) nor stride length (r = -0.05) and frequency (r = -0.05). The absence of correlation between the changes in VO₂ and MVC suggests that strength loss was not a key factor affecting RE.

Impact of high sodium intake on blood pressure and functional sympatholysis during rhythmic handgrip exercise

High dietary sodium intake is a risk factor for arterial hypertension; given that the ability to overcome sympathetically mediated vasoconstriction (functional sympatholysis) is attenuated in individuals with hypertension, we investigated the cardiovascular responses to high salt (HS) intake in healthy humans. We hypothesized that a HS intake of 15 g/day for 7 days would attenuate functional sympatholysis and augment the blood pressure response to handgrip exercise (HGE). Thirteen participants (6 males, 7 females) underwent 2 individual days of testing. Beat-by-beat blood pressure and heart rate were recorded throughout the trial on the non-exercising limb. Forearm blood flow was derived from ultrasonography on the brachial artery of the exercising limb. Participants then underwent a flow-mediated dilation (FMD) test. Next, a submaximal HGE was performed for 7 min with lower body negative pressure initiated during minutes 5-7. A single spot urine sample revealed a significant increase in sodium excretion during the HS conditions (p < 0.01). FMD was reduced during the HS condition. Mean arterial pressure was significantly higher during HS intake. No alteration to functional sympatholysis was found between conditions (p > 0.05). In summary, HS intake increases blood pressure without impacting functional sympatholysis or blood pressure responsiveness during HGE. These findings indicate that brachial artery dysfunction precedes an inefficient functional sympatholysis. Novelty Functional sympatholysis was not impacted by 1 week of high sodium intake. High sodium intake augmented the rate pressure product during handgrip exercise in healthy humans.

Effects of acute grape seed extract supplementation on muscle damage after eccentric exercise: A randomized, controlled clinical trial

Background/objective

High intensity eccentric exercise causes muscle damage. Polyphenol supplementation is one nutritional intervention available to limit muscle damage, but there is a lack of published data concerning the use of polyphenol-rich grape seed extract (GSE). This study investigated the effect of acute GSE supplementation on muscle damage markers after eccentric exercise.

Methods

Sixteen healthy male university students (mean age: 20.3 ± 0.4 years, height: 176.1 ± 4.7 cm, weight: 69.9 ± 10.2 kg) were included. Participants were randomly assigned to GSE group (n = 8) or placebo group (n = 8); 300 mg/day of GSE or placebo was consumed from the time of eccentric exercise to 72 h after exercise. For the eccentric exercise, the elbow flexor muscle was activated using a modified preacher curl machine at 25 repetitions for 2 sets. For the muscle damage markers, maximal muscle strength, muscle soreness, and creatine kinase (CK) level were measured.

Results

There was no difference in maximal muscle strength and muscle soreness between groups in the recovery stage after eccentric exercise (p > 0.05); CK level, a marker of cell membrane damage, was significantly decreased 96 h after exercise in the GSE group compared with the placebo group (p < 0.05).

Conclusion

Acute GSE supplement can be an effective way to decrease cellular membrane damage after eccentric exercise. These results could be helpful in the application of GSE supplementation as a nutritional intervention to reduce muscle damage after high intensity strength training, especially in the early stage of a new strength training program. However, a larger scale study is necessary to validate these results.

Vasoconstrictor responsiveness through alterations in relaxation time and metabolic rate during rhythmic handgrip contractions

Increasing the relaxation phase of the contraction-relaxation cycle will increase active skeletal muscle blood flow ( Q ˙ m ). However, it remains unknown if this increase in Q ˙ m alters the vasoconstriction responses in active skeletal muscle. This investigation determined if decreasing mechanical impedance would impact vasoconstriction of the active skeletal muscle. Eight healthy men performed rhythmic handgrip exercise under three different conditions; "low" duty cycle at 20% maximal voluntary contraction (MVC), "low" duty cycle at 15% MVC, and "high" duty cycle at 20% MVC. Relaxation time between low and high duty cycles were 2.4 sec versus 1.5 sec, respectively. During steady-state exercise lower body negative pressure (LBNP) was used to evoke vasoconstriction. Finger photoplethysmography and Doppler ultrasound derived diameters and velocities were used to measure blood pressure, forearm blood flow (FBF: mL min-1 ) and forearm vascular conductance (FVC: mL min-1  mmHg) throughout testing. The low duty cycle increased FBF and FVC versus the high duty cycle under steady-state conditions at 20% MVC (P < 0.01). The high duty cycle had the greatest attenuation in %ΔFVC (-1.9 ± 3.8%). The low duty cycle at 20% (-13.3 ± 1.4%) and 15% MVC (-13.1 ± 2.5%) had significantly greater vasoconstriction than the high duty cycle (both: P < 0.01) but were not different from one another (P = 0.99). When matched for work rate and metabolic rate ( V ˙ O 2 ), the high duty cycle had greater functional sympatholysis than the low duty cycle. However, despite a lower V ˙ O 2 , there was no difference in functional sympatholysis between the low duty cycle conditions. This may suggest that increases in Q ˙ m play a role in functional sympatholysis when mechanical compression is minimized.

Lower cutaneous microvascular reactivity in adult cancer patients receiving chemotherapy

Cancer patients with a history of anticancer chemotherapy are at an increased cardiovascular disease risk compared with cancer-free populations. Therefore, we tested the hypothesis that cancer patients receiving adjuvant chemotherapy would have a lower cutaneous microvascular reactivity and lower endothelium-dependent flow-mediated dilation (FMD) of the brachial artery compared with matched cancer-free control subjects. To test this hypothesis, we performed a case control study with seven cancer patients receiving adjuvant chemotherapy and seven matched healthy reference control subjects. Red blood cell flux was measured as an index of cutaneous blood flow via laser Doppler flowmetry. Acetylcholine (ACh)-mediated vasodilation was determined by iontophoresis. Data were expressed as percent increase in cutaneous vascular conductance. Endothelium-dependent FMD of the brachial artery via ultrasonography was determined as an index of macrovessel endothelial function. Cutaneous microvascular reactivity was attenuated in cancer patients compared with control subjects [cancer: 959.9 ± 187.3%, control: 1,556.8 ± 222.2%; P = 0.03, effect size (ES) = 1.1]. Additionally, cancer patients demonstrated a significantly lower area under the curve response to ACh iontophoresis compared with healthy control subjects. Brachial artery FMD was also significantly lower in cancer patients compared with control subjects (cancer: 2.2 ± 0.6%, control: 6.6 ± 1.4%; P = 0.006, ES = 1.6), which was significantly associated with measurements of microvascular reactivity. These findings suggest that decreases in vascular reactivity can occur during cancer chemotherapy, which may have implications for the long-term risk of cardiovascular disease morbidity and mortality. NEW & NOTEWORTHY Cancer survivors treated with chemotherapy experience an increased risk of cardiovascular events, linked to both cardiac and vascular toxicity. The major finding of this study is that microvascular reactivity and macrovascular endothelium-dependent flow-mediated dilation are lower in cancer patients currently receiving adjuvant chemotherapy compared with healthy counterparts.

Effect of exercise-induced muscle damage on vascular function and skeletal muscle microvascular deoxygenation

This paper investigated the effects of unaccustomed eccentric exercise‐induced muscle damage (EIMD) on macro‐ and microvascular function. We tested the hypotheses that resting local and systemic endothelial‐dependent flow‐mediated dilation (FMD) and microvascular reactivity would decrease, V˙O2max would be altered, and that during ramp exercise, peripheral O₂ extraction, evaluated via near‐infrared‐derived spectroscopy (NIRS) derived deoxygenated hemoglobin + myoglobin ([HHb]), would be distorted following EIMD. In 13 participants, measurements were performed prior to (Pre) and 48 h after a bout of knee extensor eccentric exercise designed to elicit localized muscle damage (Post). Flow‐mediated dilation and postocclusive reactive hyperemic responses measured in the superficial femoral artery served as a measurement of local vascular function relative to the damaged tissue, while the brachial artery served as an index of nonlocal, systemic, vascular function. During ramp‐incremental exercise on a cycle ergometer, [HHb] and tissue saturation (TSI%) in the m. vastus lateralis were measured. Superficial femoral artery FMD significantly decreased following EIMD (pre 6.75 ± 3.89%; post 4.01 ± 2.90%; P < 0.05), while brachial artery FMD showed no change. The [HHb] and TSI% amplitudes were not different following EIMD ([HHb]: pre, 16.9 ± 4.7; post 17.7 ± 4.9; TSI%: pre, 71.0 ± 19.7; post 71.0 ± 19.7; all P > 0.05). At each progressive increase in workload (i.e., 0–100% peak), the [HHb] and TOI% responses were similar pre‐ and 48 h post‐EIMD (P > 0.05). Additionally, V˙O2max was similar at pre‐ (3.0 ± 0.67 L min⁻¹) to 48 h post (2.96 ± 0.60 L min⁻¹)‐EIMD (P > 0.05). Results suggest that moderate eccentric muscle damage leads to impaired local, but not systemic, macrovascular dysfunction.