Comparison between old and young men for changes in makers of muscle damage following voluntary eccentric exercise of the elbow flexors

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.

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.

Benefits of Eccentric Training with Emphasis on Demands of Daily Living Activities and Feasibility in Older Adults: A Literature Review

Aging is associated with a decline in physical capabilities and several other health-related conditions. One of the most common age-related processes is sarcopenia. Sarcopenia is usually accompanied with a decline in skeletal muscle mass and physical functioning. A decrease in these markers usually impacts basic daily living activities (DLAs), which become somewhat harder to accomplish for older individuals. Several research studies have examined the demands of DLA in older individuals with results indicating that activities such as walking, sitting, standing, stair climbing, stair descending, and running generate high demands on older adults. The forces that act on individuals are in most cases equal or multiple times higher relative to their body mass. For instance, it was reported that the GRF (ground reaction force) during stair descent ranged from 1.43 to 1.50 of BW (body weight) in an older population. Even higher demands were recorded during other related activities. These demands of DLA raise the question of appropriate rehabilitative or training management procedures. During the past decades, an eccentric form of resistance training gained popularity due to its effectiveness and lower metabolic demands, which seems to be an appropriate method to develop and maintain a basic level of strength capabilities in higher age. Multiple factors of eccentric training have been examined including modality of exercise, intensity, frequency, and safety of the elderly. Several modalities of eccentric exercise have been shown to be effective including traditional methods, as well as machine-based ones, with or without using some equipment. The studies included in this review varied in intensity from low to high; however, the most frequently used intensity was ≥50% of the maximal eccentric strength during two or three eccentric sessions per week. Importantly, the prevalence of injury of older adults appears to have been low to none, highlighting the safety of this approach. In summary, eccentric training prescriptions for older adults should consider the demands of DLA and the characteristics of the elderly for appropriate management of training recommendations.

Changes in Muscle Shear Modulus and Urinary Titin N-Terminal Fragment after Eccentric Exercise

This study aimed to investigate the relationship between the muscle shear modulus of the biceps brachii, urinary titin N-terminal fragment (UTF), and other damage markers after eccentric exercise. Seventeen healthy males performed five sets of ten eccentric exercises with dumbbells weighing 50% of the maximum voluntary contraction (MVC) at the elbow joint. Muscle shear modulus with range of interest set to only biceps brachii muscle measured by ultrasound shear wave elastography, UTF, MVC, range of motion (ROM), and soreness (SOR) were recorded before, immediately after, and 1, 24, 48, 72, 96, and 168 h after eccentric exercise. Each marker changed in a time course pattern, as found in previous studies. The peak shear modulus showed a moderate negative correlation with peak MVC (r = -0.531, P < 0.05) and a strong positive correlation with peak UTF (r = 0.707, P < 0.01). Our study results revealed a significant relationship between muscle strength, shear modulus measured by ultrasound SWE, and titin measured by UTF, as a non-invasive damage marker after eccentric exercise to track changes in EIMD.

Applications of Eccentric Exercise to Improve Muscle and Mobility Function in Older Adults

Muscle aging ultimately leads to the deterioration of human physiological functioning, including declining muscle strength, loss of muscle mass, and decreased quality of life in advanced age. Eccentric exercise is a key intervention that has the potential to ameliorate this problem. Recent studies have focused on evidence-based exercise interventions to prevent declines in muscle strength and physical function in older adults. This paper reviewed relevant literature on the use of eccentric exercise to improve muscle and mobility function in older adults. We explained not only the changes in mobility that occur with aging but also the rationale for and positive effects of eccentric intervention in older adults. We also explored several proposed mechanisms for the intramuscular changes caused by eccentric muscle contraction and considered the safety and side effects accompanying eccentric training. We concluded by suggesting that eccentric exercise is an exercise modality that can potentially improve muscle strength and enhance mobility in older adults.

Eccentric Exercise: Adaptations and Applications for Health and Performance

The goals of this narrative review are to provide a brief overview of the muscle and tendon adaptations to eccentric resistance exercise and address the applications of this form of training to aid rehabilitative interventions and enhance sports performance. This work is centered on the author contributions to the Special Issue entitled "Eccentric Exercise: Adaptations and Applications for Health and Performance". The major themes from the contributing authors include the need to place greater attention on eccentric exercise mode selection based on training goals and individual fitness level, optimal approaches to implementing eccentric resistance exercise for therapeutic purposes, factors that affect the use of eccentric exercise across the lifespan, and general recommendations to integrate eccentric exercise in athletic training regimens. The authors propose that movement velocity and the absorption or recovery of kinetic energy are critical components of eccentric exercise programming. Regarding the therapeutic use of eccentric resistance training, patient-level factors regarding condition severity, fitness level, and stage of rehabilitation should govern the plan of care. In athletic populations, use of eccentric exercise may improve movement competency and promote improved safety and performance of sport-specific tasks. Eccentric resistance training is a viable option for youth, young adults, and older adults when the exercise prescription appropriately addresses program goals, exercise tolerability, and compliance. Despite the benefits of eccentric exercise, several key questions remain unanswered regarding its application underscoring the need for further investigation.

Recovery From Eccentric Squat Exercise in Resistance-Trained Young and Master Athletes With Similar Maximum Strength: Combining Cold Water Immersion and Compression

The aim of this study was to investigate whether recovery from eccentric squat exercise varies depending on age and to assess whether the use of a mixed-method recovery (MMR) consisting of cold water immersion and compression tights benefits recovery. Sixteen healthy and resistance-trained young (age, 22.1±2.1years; N=8) and master male athletes (age, 52.4±3.5years; N=8), who had a similar half squat 1-repetition maximum relative to body weight, completed two identical squat exercise training sessions, separated by a 2-week washout period. Training sessions were followed by either MMR or passive recovery (PR). Internal training loads [heart rate and blood lactate concentration (BLa)] were recorded during and after squat sessions. Furthermore, maximal voluntary isometric contraction (MVIC) force, countermovement jump (CMJ) height, resting twitch force of the knee extensors, serum concentration of creatine kinase (CK), muscle soreness (MS), and perceived physical performance capability (PPC) were determined before and after training as well as after 24, 48, and 72h of recovery. A three-way mixed ANOVA revealed a significant time effect of the squat protocol on markers of fatigue and recovery (p<0.05; decreased MVIC, CMJ, twitch force, and PPC; increased CK and MS). Age-related differences were found for BLa, MS, and PPC (higher post-exercise fatigue in younger athletes). A significant two-way interaction between recovery strategy and time of measurement was found for MS and PPC (p<0.05; faster recovery after MMR). In three participants (two young and one master athlete), the individual results revealed a consistently positive response to MMR. In conclusion, master athletes neither reach higher fatigue levels nor recover more slowly than the younger athletes. Furthermore, the results indicate that MMR after resistance exercise does not contribute to a faster recovery of physical performance, neuromuscular function, or muscle damage, but promotes recovery of perceptual measures regardless of age.

Acute and Delayed Effects of Time-Matched Very Short "All Out" Efforts in Concentric vs. Eccentric Cycling

BACKGROUND

To the authors' knowledge, there have been no studies comparing the acute responses to "all out" efforts in concentric (isoinertial) vs. eccentric (isovelocity) cycling.

METHODS

After two familiarization sessions, 12 physically active men underwent the experimental protocols consisting of a 2-min warm-up and 8 maximal efforts of 5 s, separated by 55 s of active recovery at 80 rpm, in concentric vs. eccentric cycling. Comparisons between protocols were conducted during, immediately after, and 24-h post-sessions.

RESULTS

Mechanical (Work: 82,824 ± 6350 vs. 60,602 ± 8904 J) and cardiometabolic responses (mean HR: 68.8 ± 6.6 vs. 51.3 ± 5.7% HRmax, lactate: 4.9 ± 2.1 vs. 1.8 ± 0.6 mmol/L) were larger in concentric cycling (p < 0.001). The perceptual responses to both protocols were similarly low. Immediately after concentric cycling, vertical jump was potentiated (p = 0.028). Muscle soreness (VAS; p = 0.016) and thigh circumference (p = 0.045) were slightly increased only 24-h after eccentric cycling. Serum concentrations of CK, BAG3, and MMP-13 did not change significantly post-exercise.

CONCLUSIONS

These results suggest the appropriateness of the eccentric cycling protocol used as a time-efficient (i.e., ~60 kJ in 10 min) and safe (i.e., without exercise-induced muscle damage) alternative to be used with different populations in future longitudinal interventions.

The influence of age on the recovery from worksite resistance exercise in career firefighters

Resistance exercise is an important strategy to reduce injuries and improve performance in the fire service. However, given the large age range of firefighters, it is important to determine if age influences their recovery following an acute bout of resistance exercise.

PURPOSE

To examine the changes in indirect markers of muscle damage in young and older firefighters following a feasible worksite resistance exercise routine.

METHODS

Nineteen young (25.5 ± 3.4 years) and 19 older male career firefighters (50.3 ± 3.5 years) completed pre-testing, an acute bout of resistance exercise, and post-testing at 24, 48, and 72 h post-exercise at their fire station. Prior to all testing, firefighters completed a work-related fatigue (WRF) questionnaire to account for potential unanticipated differences in previous shift workloads. Testing included perceived muscle soreness, ultrasonography to quantify muscle size and echo intensity (EI) of the vastus lateralis (VL) and biceps brachii (BB), countermovement jump (CMJ) height and velocity, upper body (UB) peak force (PF), lower body (LB) PF and rapid force, and electromyographic (EMG) amplitude of the VL. The resistance training session included 3 sets of 8-10 repetitions of a deadlift, shoulder press, lunge, and upright row exercise at 80% 1-RM. All recovery variables were analyzed using a linear mixed model, controlling for WRF.

RESULTS

There was no interaction (age × time) for any of the variables and a similar training volume were completed between groups (P ≥ 0.171). Muscle soreness, CMJ height and velocity, UB PF, LB rapid force and EMG amplitude at later time intervals (100-200 ms), and VL and BB muscle size were altered from baseline (P ≤ 0.044) for 48, 24, 48, 72, and 72 h post-exercise, respectively. Young firefighters exhibited greater CMJ height and velocity, LB PF, LB rapid force (200 ms), and lower VL EI values than the older firefighters (P ≤ 0.047).

CONCLUSIONS

Age did not influence the recovery from an acute bout of worksite resistance exercise in firefighters. However, UB muscle strength, CMJ performance, and LB rapid force production were reduced 24-72 h post-exercise. Appropriately scheduled and chronic on-duty resistance training may mitigate these decrements.

Functional recovery from eccentric injury is maintained in sarcopenic mouse muscle

Background

Eccentric contractions induce muscle damage (EIMD) that compromises muscle function. Poor recovery from EIMD has been suggested to be a contributor to the decline in muscle function evident in sarcopenia, but it is unclear which aspects of muscle function are more susceptible to disruption by EIMD in old versus young muscle. The purpose of this study was to determine the extent of impairment in contractile function (force, fatigue, tetanus and twitch kinetics) during the recovery from EIMD in very old (VO) mice compared to young adult (YA).

Methods

Male CB6F1 were obtained from National Institure of Aging colony. VO mice were 29-31 months of age, and YA mice were 7-9 months of age. The plantarflexor muscles were subjected to 20 eccentric contractions in vivo to induce injury (EIMD). Changes in tetanic force and kinetics were assessed before EIMD, immediately after EIMD and 3 days after EIMD (3dEIMD). Force-frequency and rates of fatigue were assessed 3d-EIMD and compared with baseline. Histological analysis was conducted in injured and non-injured contralateral gastrocnemius muscle.

Results

There was a greater loss in isometric tetanic force immediately following EIMD in VO compared with YA (-31.6% ± 10.4 vs. -21.7% ± 6.0, P < 0.05). At 3d-EIMD, the rate of contraction of tetanus began to recover in VO, but not in YA (20.8% vs. -6.8%, P < 0.05), whereas the extent of recovery of force tended to be greater in VO than YA (39.3% vs. 17.1%, P = 0.08) when compared with tetanic function immediately after injury. Compared with function pre-injury (baseline), VO and YA had similar deficits in tetanic force (-7.3% ± 5.3 vs. -9.2% ± 6.0, respectively) and kinetics at Day 3. Twitch kinetics (rate of relaxation) recovered faster in VO compared with YA. The rate of muscle fatigue was similar to baseline values, with VO continuing to be more fatigue resistant than YA 3d-EIMD. There were no detectable differences in muscle mass or myofibre cross-sectional area despite continued deficits in force following EIMD in either age group.

Conclusions

Despite clear functional deficits and greater susceptibility to injury, aged sarcopenic muscle exhibited a similar ability to recover contractile function to younger muscle following EIMD. In addition, neither age group showed accelerated muscle fatigue in the recovery phase after EIMD; thus, sarcopenic mouse muscles do not appear to be more susceptible to long-term functional impairment than young healthy muscles.

Aging and Recovery After Resistance-Exercise-Induced Muscle Damage: Current Evidence and Implications for Future Research

Aging is anecdotally associated with a prolonged recovery from resistance training, though current literature remains equivocal. This brief review considers the effects of resistance training on indirect markers of muscle damage and recovery (i.e., muscle soreness, blood markers, and muscle strength) in older males. With no date restrictions, four databases were searched for articles relating to aging, muscle damage, and recovery. Data from 11 studies were extracted for review. Of these, four reported worse symptoms in older compared with younger populations, while two have observed the opposite, and the remaining studies (n = 6) proposed no differences between age groups. It appears that resistance training can be practiced in older populations without concern for impaired recovery. To improve current knowledge, researchers are urged to utilize more ecologically valid muscle-damaging bouts and investigate the mechanisms which underpin the recovery of muscle soreness and strength after exercise in older populations.

Massage enhances recovery following exercise-induced muscle damage in older adults

To examine efficacy of cold water immersion (CWI) and massage as recovery techniques on joint position sense, balance, and fear of falling following exercise-induced muscle damage in older adults. Seventy-eight older men and women performed a single bout of strength training on the calf muscles (3 exercises with 4 sets of 10 reps with 75% of 1RM) to induce muscle damage. After the damaging exercise, participants received either a 15-minute massage on calf muscles, or a CWI of the lower limb in cold water (15 ± 1°C) for 15 minute, or passive rest. Interventions were applied immediately after the exercise protocol and at 24, 48, and 72 hours post-exercise. Muscle pain, calf muscle strength, joint position sense, dynamic balance, postural sway, and fear of falling were measured at each time point. Repeated application of massage after EIMD relieved muscle pain, attenuated the loss of muscle strength and joint position senses, reduce balance impairments, and fear of falling in older adults (P ≤ .05). However, repeated applications of CWI, despite relieving muscle pain (P ≤ .05), did not attenuate the loss of muscle strength, joint position senses, balance impairments, and fear of falling. CWI had only some modest effects on muscle pain, but massage attenuated EIMD symptoms and the related impairments in muscle strength, joint position sense, balance, and postural sway in untrained older individuals. Therefore, older exercisers who plan to participate in strength training can benefit from massage for recovery from muscle damage indices and balance to decrease falling risk during the days following strength training.

Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults

A bout of maximal lengthening contractions is known to produce muscle damage, but confers protection against subsequent damaging bouts, with both tending to be lower in older adults. Neural factors contribute to this adaptation, but the role of the corticospinal pathway remains unclear. Twelve young (27 ± 5 yr) and 11 older adults (66 ± 4 yr) performed two bouts of 60 maximal lengthening dorsiflexions 2 weeks apart. Neuromuscular responses were measured preexercise, immediately postexercise, and at 24 and 72 h following both bouts. The initial bout resulted in prolonged reductions in maximal voluntary torque (MVC; immediately postexercise onward, P < 0.001) and increased creatine kinase (from 24 h onward, P = 0.001), with both responses being attenuated following the second bout ( P < 0.015), demonstrating adaptation. Smaller reductions in MVC following both bouts occurred in older adults ( P = 0.005). Intracortical facilitation showed no changes ( P ≥ 0.245). Motor-evoked potentials increased 24 and 72 h postexercise in young ( P ≤ 0.038). Torque variability ( P ≤ 0.041) and H-reflex size ( P = 0.024) increased, while short-interval intracortical inhibition (SICI; P = 0.019) and the silent period duration (SP) decreased ( P = 0.001) in both groups immediately postexercise. The SP decrease was smaller following the second bout ( P = 0.021), and there was an association between the change in SICI and reduction in MVC 24 h postexercise in young adults ( R = −0.47, P = 0.036). Changes in neurophysiological responses were mostly limited to immediately postexercise, suggesting a modest role in adaptation. In young adults, neural inhibitory changes are linked to the extent of MVC reduction, possibly mediated by the muscle damage–related afferent feedback. Older adults incurred less muscle damage, which has implications for exercise prescription.

NEW & NOTEWORTHY This is the first study to have collectively assessed the role of corticospinal, spinal, and intracortical activity in muscle damage attenuation following repeated bouts of exercise in young and older adults. Lower levels of muscle damage in older adults are not related to their neurophysiological responses. Neural inhibition transiently changed, which might be related to the extent of muscle damage; however, the role of processes along the corticospinal pathway in the adaptive response is limited.

Effect of eccentric exercise on markers of muscle damage in patients with chronic obstructive pulmonary disease

Background: Eccentric exercise may be considered as an attractive alternative to conventional exercise in pulmonary rehabilitation (PR) for patients with chronic obstructive pulmonary disease (COPD). However, due to muscle damage associated with eccentric exercise, there has been reluctance in using this exercise form in PR.Objective: The aim of the present study was to investigate the effect of eccentric exercise on markers of muscle damage in patients with COPD.Methods: We analyzed 14 patients with moderate-severe COPD and 14 age-matched healthy controls. Both groups performed submaximal eccentric exercise of the elbow flexors. Muscle soreness (MS), maximum voluntary isometric contraction (MVC) of the elbow flexors, elbow range of motion (ROM), upper arm circumference (CIR), and biochemical markers such as creatine Kinase (CK) and lactate Dehydrogenase (LDH) were measured at pre-exercise, 24 h, 48 h, and 72 h following submaximal eccentric exercise.Results: There was a significant difference in markers of muscle damage, MS (p = .002), MVC (p < .001), ROM (p = .010), CIR (p < .001), and LDH (p = .001). However, no significant differences were observed in the activity of CK (p = .261) between COPD and control group following eccentric exercise which indicates greater degree of muscle damage in COPD as compared with control.Conclusion: Sub-maximal eccentric exercise causes significantly greater muscle damage in elderly COPD patients than healthy controls. Therefore, initial exercise should be progressed with lower intensities to prevent undue muscle damage in these patients.

Exercise-Induced Muscle Damage and Recovery in Young and Middle-Aged Males with Different Resistance Training Experience

This study compared the time course of recovery after a squatting exercise in trained young (YG; n = 9; age 22.3 ± 1.7 years) and trained (MT; n = 9; 39.9 ± 6.2 years) and untrained (MU; n = 9; age 44.4 ± 6.3 years) middle-aged males. Before and at 24 and 72 h after 10 × 10 squats at 60% one-repetition maximum (1RM), participants provided measurements of perceived muscle soreness (VAS), creatine kinase (CK), maximal voluntary contraction (MVC), voluntary activation (VA), and resting doublet force of the knee extensors and squatting peak power at 20% and 80% 1RM. When compared to the YG males, the MT experienced likely and very likely moderate decrements in MVC, resting doublet force, and peak power at 20% and 80% 1RM accompanied by unclear differences in VAS, CK, and VA after the squatting exercise. MU males, compared to MT, experienced greater alterations in peak power at 20% and 80% 1RM and VAS. Alterations in CK, MVC, VA, and resting doublet force were unclear at all time-points between the middle-aged groups. Middle-aged males experienced greater symptoms of muscle damage and an impaired recovery profile than young resistance trained males. Moreover, regardless of resistance training experience, middle-aged males are subject to similar symptoms after muscle-damaging lower-body exercise.

Immediate effects of transcutaneous electrical nerve stimulation (TENS) administered during resistance exercise on pain intensity and physical performance of healthy subjects: a randomized clinical trial

PURPOSE

Exercise-induced muscle pain is a self-limiting condition which impacts physical activity habits. Transcutaneous electrical nerve stimulation (TENS) promotes pain reduction and functional improvement in different pain conditions. We propose that applying TENS during exercise might reduce pain and improve physical performance. Thus, we aimed to investigate immediate effects of TENS applied during resistance exercise.

METHODS

Healthy subjects of both sexes, irregularly active or sedentary were assigned into two groups: active (n = 24) or placebo (n = 22) TENS. The study was conducted over five moments: on day 0, subjects were recruited, on day 1 subjects performed the one-repetition maximum test (1RM); 72 h later, on day 2, 1RM was retested; 48 h later, on day 3, TENS was applied during a functional-resisted exercise protocol for upper limbs (bench press and rowing), with an intensity of 80% of 1RM; and 24 h after, on day 4, subjects were reevaluated. Assessment included pain intensity at rest and with movement, pressure pain thresholds, and muscle fatigue.

RESULTS

TENS did not reduce pain intensity when compared to placebo (p > 0.05). TENS reduce PPT in the latissmus dorsi: p = 0.02 and anterior tibialis: p = 0.04 in immediate reassessment. Immediate effects of TENS were significant for fatigue perception at rest (p = 0.01) and number of maximum repetitions during exercise sets, starting from the 5th set of rowing exercise (p = 0.002).

CONCLUSION

Our results show that TENS did not reduce pain perception in healthy individuals, but its use induced increased muscle action, contributing to a greater fatigue perception.

Concurrent treatment with ursolic acid and low-intensity treadmill exercise improves muscle atrophy and related outcomes in rats

The objective of this study was to analyze the concurrent treatment effects of ursolic acid (UA) and low-intensity treadmill exercise and to confirm the effectiveness of UA as an exercise mimetic to safely improve muscle atrophy-related diseases using Sprague-Dawley (SD) rats with skeletal muscle atrophy. Significant muscle atrophy was induced in male SD rats through hind limb immobilization using casting for 10 days. The muscle atrophy-induced SD rats were group into four: SED, sedentary; UA, daily intraperitoneal UA injection, 5 mg/kg; EX, low-intensity (10–12 m/min, 0° grade) treadmill exercise; and UEX, daily intraperitoneal UA injection, 5 mg/kg, and low-intensity (10–12 m/min, 0° grade) treadmill exercise. After 8 weeks of treatment, endurance capacity was analyzed using a treadmill, and tissues were extracted for analysis of visceral fat mass, body weight, muscle mass, expression of muscle atrophy- and hypertrophy-related genes, and endurance capacity. Although the effects of body weight gain control, muscle mass increase, and endurance capacity improvement were inadequate in the UA group, significant results were confirmed in the UEX group. The UEX group had significantly reduced body weight and visceral fat, significantly improved mass of tibialis anterior and gastrocnemius muscles, and significantly decreased atrophy-related gene expression of MuRF1 and atrogin-1, but did not have significant change in hypertrophy-related gene expression of Akt and mTOR. The endurance capacity was significantly improved in the EX and UEX groups. These data suggest that concurrent treatment with low-intensity exercise and UA is effective for atrophy-related physical dysfunctions.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The Effects of Resistance Exercise on Muscle Damage, Position Sense, and Blood Redox Status in Young and Elderly Individuals

Background: The purpose of the present investigation was to study the possible differences between young and elderly individuals regarding muscle damage, position sense, and oxidative stress biomarkers in response to resistance eccentric-biased exercise. Methods: Ten young and 10 elderly individuals performed a bout of resistance exercise (i.e., squat exercise). Muscle damage indices (i.e., isometric peak torque, range of movement, delayed onset muscle soreness, and creatine kinase), position sense, and oxidative stress biomarkers (i.e., protein carbonyls and reduced glutathione) were assessed before and 48 h post exercise. Results: The main effect of time was significant for all measured parameters, indicating that resistance exercise that includes a large eccentric component causes muscle damage, disturbs position sense, and induces oxidative stress. However, no significant main effect of group or time × group interaction was found for all measured parameters (except isometric peak torque), indicating similar responses to resistance exercise for both young and the elderly individuals. Conclusion: There are no differences between young and elderly individuals regarding muscle damage, position sense, and oxidative stress after resistance exercise, while elderly individuals have lower muscle strength and seem to have a tendency for greater baseline oxidative stress compared to young individuals.

Age-related functional changes and susceptibility to eccentric contraction-induced damage in skeletal muscle cell

Depending upon external loading conditions, skeletal muscles can either shorten, lengthen, or remain at a fixed length as they produce force. Fixed-end or isometric contractions stabilize joints and allow muscles to act as active struts during locomotion. Active muscles dissipate energy when they are lengthened by an external force that exceeds their current force producing capacity. These unaccustomed eccentric activities often lead to muscle weakness, soreness, and inflammation. During aging, the ability to produce force under these conditions is reduced and appears to be due to not only reductions in muscle mass but also to alterations in the basic mechanisms of contraction. These alterations include impairments in the excitation–contraction process, and the action of the cross-bridges. Also, it is well known that age-related skeletal muscle atrophy is characterized by a preferential atrophy of fast fibers, and increased susceptibility to fast muscle fiber when aged muscles are exposed to eccentric contraction followed by the impaired recovery process has been reported. Taken together, the selective loss of fast muscle fiber in aged muscle could be affected by eccentric-induced muscle damage, which has significant implication to identify the etiology of the age-related functional changes. Therefore, in this review the alteration of age-related muscle function and its impact to/of eccentric induced muscle damage and recovery will be addressed in detail.

Dor muscular e atividade de creatina quinase após ações excêntricas: uma análise de cluster

INTRODUÇÃO: O exercício excêntrico máximo promove queda da capacidade de geração de força, aumento de dor muscular de início tardio (DMIT) e extravasamento de creatina quinase (CK) no sangue. No entanto, essas respostas ao exercício excêntrico demonstram alta variabilidade interindivíduos.OBJETIVOS: Classificar e analisar essas respostas segundo a vulnerabilidade individual, por meio da magnitude da redução dos níveis de força após exercício excêntrico.MÉTODOS: Dezoito sujeitos (11 homens e sete mulheres com idade entre 18 e 71 anos) saudáveis realizaram cinco séries de seis ações excêntricas máximas para flexores do cotovelo em dinamômetro isocinético (90°s-1, amplitude de movimento de 80 a 20°). Foram analisadas contração voluntária muscular concêntrica máxima (CVM), DMIT e CK pré, pós (exceto CK), 24 h, 48 h, 72 h e 96 h após o protocolo. Os indivíduos foram classificados como "baixos" (BR) e "altos" respondedores (AR) ao pico de queda de CVM pós-exercício seguindo-se uma análise de cluster e comparação entre grupos para CVM, DMIT e CK com teste-t independente.RESULTADOS: A comparação entre BR e AR indicou maiores valores de queda de CVM para o grupo AR (AR: -30,7 ± 3,3%; BR: -14,1 ± 2,2%, p< 0,001) e maior DMIT também para o grupo AR (AR: 33,0 ± 8,6 mm; BR: 10,2 ± 2,5 mm, p= 0,033); no entanto, os valores de pico de atividade de CK não diferiram entre os grupos (AR: 232,1 ± 54,8 UI.L-1; BR: 306,1 ± 82,3 UI.L-1, p= 0,490).CONCLUSÃO: A classificação dos indivíduos em grupos de baixos e altos respondedores foi importante para demonstrar que o grupo mais responsivo à queda de força após exercício excêntrico também evidencia maiores níveis de DMIT; contudo, para a CK essa relação não pôde ser estabelecida.

Changes in oxidative stress markers and biological markers of muscle injury with aging at rest and in response to an exhaustive exercise

Purpose

The aim of this study was to evaluate whether oxidative stress markers and biomarkers of muscle injury would be affected by aging at rest and in response to an incremental exhaustive exercise.

Methods

Fifteen young (20.3±2.8 years) and fifteen older adults (65.1±3.5 years) performed an incremental cycle ergometer test to exhaustion. Before and after exercise, oxidative stress [superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione reductase (GR), ascorbic acid, α-Tocopherol, malondialdehyde (MDA)] and muscle injury [creatine kinase (CK), lactate deshydrogenase (LDH)] biomarkers were assessed.

Results

At rest, there was no difference in oxidative stress markers and LDH level between the groups, however CK was significantly higher in the young group than the elderly group (p<0.05). During recovery, in comparison with resting values, a significant increase in SOD (1092±145.9 vs. 1243±98 U/g Hb), GPX (67.4±12.7 vs. 79.2±15.6 U/g Hb) and GR (6.5±0.9 vs. 7.7±0.5 U/g Hb) activities were observed only in the young group (p<0.05). MDA has increased only in the older group (0.54±0.2 vs. 0.79±0.2 µmol/l) (p<0.01). CK increased in both groups (young group: 122.5±22.2 vs. 161.9±18.7 UI/l; older group: 88.8±34.1 vs. 111.1±25.9 UI/l) (p<0.01), however LDH has increased only in the young group (400.5±22.2 vs. 485±18.7 UI/l) (p<0.01) without alteration in the older group (382.8±34.1 vs. 418.5±25.9 UI/l).

Conclusions

These findings indicate that aging is associated with a decrease in antioxidant efficiency and an increase in oxidative stress damage. Furthermore, older adults would not more susceptible to exercise-induced muscle injury than young people.

Comparison of maximal muscle strength of elbow flexors and knee extensors between younger and older men with the same level of daily activity

Background

Aging promotes neuromuscular loss, significantly reducing muscle strength. The magnitude of loss of strength seems to be different between the limbs, probably because of differences in activities of daily living (ADL). Therefore, the present study compared the muscle strength of the elbow flexors and knee extensors in younger (n = 7, mean age 23.3 ± 1.2 years) and older (n = 5, mean age 61.8 ± 2.6 years) men matched by ADL level.

Methods

The study participants performed maximal concentric, isometric, and eccentric contractions of the elbow flexors and knee extensors using an isokinetic dynamometer following a crossover study design. Changes in the dependent variables were compared using mixed model analysis (limb versus age).

Results

The main results demonstrated that concentric, eccentric, and mean contraction torques for knee extensors were significantly (P < 0.05) higher for younger men than for elderly men. On the other hand, no statistically significant difference (P > 0.05) was found in concentric, isometric, eccentric, and mean torques for elbow flexors between younger and older individuals.

Conclusion

These results show that elbow flexors maintain better strength than knee extensors through aging, even when comparing individuals with similar ADL levels.

Power loss is greater following lengthening contractions in old versus young women

Compared with isometric and dynamic velocity-constrained (isokinetic) tasks, less is known regarding velocity-dependent (isotonic) muscle power and recovery in older adults following repeated fatiguing lengthening contractions. We investigated voluntary and evoked neuromuscular properties of the dorsiflexors in nine old (68.3 ± 6.1 years) and nine young women (25.1 ± 1.3 years) during and following 150 lengthening contractions for up to 30 min of recovery. At baseline, the old were ~21% weaker for maximum isometric voluntary contraction (MVC) torque (P < 0.05), ~21% slower for peak loaded shortening velocity (P < 0.05), and ~39% less powerful compared with the young (P < 0.05). Following the task, MVC torque was depressed equally (~28%) for both groups (P < 0.05), but power was reduced ~19% in the old and only ~8% in the young (P < 0.05). Both measures remained depressed during the 30-min recovery period. Peak twitch torque (P (t)) was ~50% lower in the old at task termination, whereas the young were unchanged. However, by 5 min of recovery, P (t) was reduced similarly (~50%) in both groups, and neither recovered by 30 min. The old were affected more by low-frequency torque depression than the young, as shown by the ~40% and ~20% decreases in the stimulated 10:50 Hz ratio at task termination respectively, whereas both groups were affected similarly (~50%) 5 min into recovery, and neither recovered by 30 min. Thus, the coexistence of fatigue and muscle damage induced by the repetitive lengthening contractions impaired excitation-contraction coupling and cross-bridge function to a greater extent in the old, leading to a more pronounced initial loss of power than the young for up to 10 min following the exercise However, power remained blunted in both groups during the 30-min recovery period. These results indicate that older women are more susceptible to power loss than young following lengthening contractions, likely owing to a greater impairment in calcium kinetics.

Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults

Muscles of old laboratory rodents experience exaggerated force losses after eccentric contractile activity. We extended this line of inquiry to humans and investigated the influence of fiber myosin heavy chain (MHC) isoform content on the injury process. Skinned muscle fiber segments, prepared from vastus lateralis biopsies of elderly men and women (78 ± 2 years, N = 8), were subjected to a standardized eccentric contraction (strain, 0.25 fiber length; velocity, 0.50 unloaded shortening velocity). Injury was assessed by evaluating pre- and post-eccentric peak Ca(2+)-activated force per fiber cross-sectional area (F (max)). Over 90% of the variability in post-eccentric F (max) could be explained by a multiple linear regression model consisting of an MHC-independent slope, where injury was directly related to pre-eccentric F (max), and MHC-dependent y-intercepts, where the susceptibility to injury could be described as type IIa/IIx fibers > type IIa fibers > type I fibers. We previously reported that fiber type susceptibility to the same standardized eccentric protocol was type IIa/IIx > type IIa = type I for vastus lateralis fibers of 25-year-old adults (Choi and Widrick, Am J Physiol Cell Physiol 299:C1409-C1417, 2010). Modeling combined data sets revealed significant age by fiber type interactions, with post-eccentric F (max) deficits greater for type IIa and type IIa/IIx fibers from elderly vs. young subjects at constant pre-eccentric F (max). We conclude that the resistance of the myofilament lattice to mechanical strain has deteriorated for type IIa and type IIa/IIx, but not for type I, vastus lateralis fibers of elderly adults.

No adverse effects of statins on muscle function and health-related parameters in the elderly: an exercise study

The aim of the present study was to investigate the effects of a repeated bout of eccentric exercise on health-related parameters and muscle performance on subjects undergoing atorvastatin therapy. Twenty-eight elderly men participated in the investigation and were assigned either in a control (n = 14) or in a statin therapy group (n = 14). All participants performed two isokinetic eccentric exercise bouts separated by 3 weeks. Muscle damage indices, resting energy expenditure, substrate metabolism, lipid and lipoprotein profile, as well as insulin sensitivity, were evaluated before and after eccentric. No differences in muscle function were observed between the two groups either at rest or after exercise. Eccentric exercise increased resting energy expenditure, increased fat oxidation, improved lipid profile, and increased insulin resistance 2 days after both eccentric exercise bouts. However, these changes appeared to lesser extent after the second bout. No differences were observed in the responses in the health-related parameters in the control and in the statin therapy group. Eccentric exercise affected similarly the control and the atorvastatin-treated individuals. The present results indicate that atorvastatin-treated elderly individuals may participate in various physical activities, even high-intensity muscle-damaging activities, without negative impact on muscle function and adaptation.

Effects of ibuprofen topical gel on muscle soreness

PURPOSE

Muscle soreness is a common symptom after novel exercise and may influence exercise adherence. This study examined the effect of an ibuprofen topical gel and the effect of age and sex on muscle soreness after a gym exercise.

METHODS

One hundred and six participants completed six sets of 10 repetitions of the elbow and knee flexor muscles. Thirty-six hours after exercise, participants were randomized to apply an ibuprofen topical gel or placebo treatment to the affected muscle groups. Soreness evaluations were taken each hour for the first 6 h (36-42 h), then at 48, 60, 66, 72, 84, 90, 96, and 108 h after exercise. Subjects then returned to the laboratory after 3 wk and repeated the same study protocol with the opposite arm/leg and treatment.

RESULTS

We found no significant differences in soreness between the active ibuprofen gel and the placebo treatment and no difference in effectiveness between men and women or between older and younger subjects. For the placebo groups, there was no sex differences in muscle soreness; however, when the data were analyzed by dividing participants into young (18-29 yr) and old (40-65 yr) cohort, the old cohort reported significantly less soreness in response to the elbow flexion exercise than the young cohort (P < 0.01).

CONCLUSION

The results of this study suggest that the topical application of ibuprofen is not an effective treatment for muscle soreness after an unaccustomed gym exercise. Furthermore, our results show that there is no sex difference in the soreness response and that older subjects have less soreness in response to a similar exercise stimulus as young subjects.

Effects of age and glutathione levels on oxidative stress in rats after chronic exposure to stretch-shortening contractions

We investigated effects of age and glutathione synthesis inhibition on the oxidative stress status of tibialis anterior muscles from young and old Fisher 344 x Brown Norway male rats after chronic administration of stretch-shortening contractions. Oral supplementation of L: -buthionine-(S,R)-sulfoximine (BSO) inhibited glutathione synthesis. Dorsiflexor muscles in the hindlimb were exposed to 80 maximal stretch-shortening contractions (SSCs) three times per week for 4.5 weeks. We measured malondialdehyde, hydrogen peroxide (H(2)O(2)), and free isoprostanes to determine oxidative stress. Glutathione peroxidase activity was measured as an indicator of H(2)O(2) scavenging. Glutathione measurements confirmed the effectiveness of BSO treatment. In young rats, the SSC exposure protocol prevented oxidative stress and enhanced H(2)O(2) scavenging. In old rats, malondialdehyde was increased in the exposed muscle and a BSO-induced increase in H(2)O(2) was not alleviated with SSC exposure as seen in young rats. In addition, glutathione peroxidase activity and total glutathione were increased in old rats relative to their young counterparts. All comparisons were significant at the 0.05 level. Overall, BSO administration was effective in decreasing total glutathione levels and increasing H(2)O(2) levels in old and young rats exposed to SSCs. In addition, effects of chronic exposure to high-force resistive loading SSCs in active muscle from old animals are: (1) antioxidant capacity is enhanced similar to what is seen with endurance training and (2) oxidative stress is increased, probably as a consequence of the enhanced vulnerability due to aging.

Can muscle soreness after intensive work-related activities be predicted?

OBJECTIVES

It is currently unknown whether specific determinants are predictive for developing delayed onset muscle soreness (DOMS) after heavy work-related activities. The aim of this study was to analyze whether personal characteristics and performance measures are predictive for onset, intensity, and duration of DOMS after performing work-related activities during a Functional Capacity Evaluation in healthy participants.

METHODS

Included in this study were 197 healthy participants (102 men, 95 women), all working within a broad range of professions. Five groups of predictors were tested in a multiple regression analysis model: personal variables, self-reported activity, self-reported health, perceived effort during the test, and objective outcomes of the test. Twenty-three independent variables were selected and tested with a backward regression analysis.

RESULTS

The onset of DOMS could be explained for 7% by the variables: sex and the work index of the Baecke questionnaire. Variance of intensity of DOMS could be explained for 13% by the variables: age, sex, and VO2max. Variance in duration of DOMS could be explained for 8% by the variables: sex and reported emotional role limitations. Onset, intensity, and duration of DOMS remain unpredictable for 87% or more.

CONCLUSIONS

The results demonstrate that the intensity and duration of self-reported DOMS can only minimally be predicted from the candidate predictors used in this study.

Myoglobin plasma level related to muscle mass and fiber composition: a clinical marker of muscle wasting?

Progressive muscle wasting is a central feature of cancer-related cachexia and has been recognized as a determinant of poor prognosis and quality of life. However, until now, no easily assessable clinical marker exists that allows to predict or to track muscle wasting. The present study evaluated the potential of myoglobin (MG) plasma levels to indicate wasting of large locomotor muscles and, moreover, to reflect the loss of MG-rich fiber types, which are most relevant for daily performance. In 17 cancer-cachectic patients (weight loss 22%) and 27 age- and gender-matched healthy controls, we determined plasma levels of MG and creatine kinase (CK), maximal quadriceps muscle cross-sectional area (CSA) by magnetic resonance imaging, muscle morphology and fiber composition in biopsies from the vastus lateralis muscle, body cell mass (BCM) by impedance technique as well as maximal oxygen uptake (VO(2)max). In cachectic patients, plasma MG, muscle CSA, BCM, and VO(2)max were 30-35% below control levels. MG showed a significant positive correlation to total muscle CSA (r = 0.65, p < 0.001) and to the CSA fraction formed by type 1 and 2a fibers (r = 0.80, p < 0.001). However, when adjusted for body height and age by multiple regression, MG yielded a largely improved prediction of total CSA (multiple r = 0.83, p < 0.001) and of fiber type 1 and 2a CSA (multiple r = 0.89, p < 0.001). The correlations between CK and these muscle parameters were weaker, and elevated CK values were observed in 20% of control subjects despite a prior abstinence from exercise for 5 days. In conclusion, plasma MG, when adjusted for anthropometric parameters unaffected by weight, may be considered as a novel marker of muscle mass (CSA) indicating best the mass of MG-rich type 1 and 2a fibers as well as VO(2)max as an important functional readout. CK plasma levels appear to be less reliable because prolonged increases are observed in even subclinical myopathies or after exercise. Notably, cancer-related muscle wasting was not associated with increases in plasma MG or CK in this study.

Changes in markers of muscle damage of middle-aged and young men following eccentric exercise of the elbow flexors

It is well documented that unaccustomed eccentric exercise induces muscle damage, but the responses of middle-aged individuals to a bout of eccentric exercise have not been reported. The purpose of this study was to compare changes in indirect markers of muscle damage following eccentric exercise of the elbow flexors between 12 young (age: 19.4+/-0.4 years, height: 173.5+/-2.0cm, body mass: 65.8+/-3.5kg) and 12 middle-aged men (48.0+/-2.1 years, 169.5+/-1.7cm, 67.3+/-1.6kg). It was hypothesized that middle-aged men would be more susceptible to muscle damage than young men. All subjects performed six sets of five eccentric actions of the elbow flexors using a dumbbell of 40% of maximal isometric strength (MVC). Changes in MVC, elbow joint angles and range of motion, upper arm circumference, plasma creatine kinase activity and myoglobin concentration, and muscle soreness before, immediately after, and 1, 2, 3, and 4 days after exercise were compared between the young and middle-aged groups by a two-way repeated measures ANOVA. All criterion measures changed significantly (P<0.05) after exercise, but no significant differences in the changes in the measures except for muscle soreness were evident between groups. Development of muscle soreness after exercise was significantly (P<0.05) lower (approximately a half of the value) for the middle-aged group compared with the young group. These results did not support the hypothesis that middle-aged men would be more susceptible to muscle damage than young men.

Fluctuations of isometric force after eccentric exercise of the elbow flexors of young, middle-aged, and old men

This study compared force fluctuations during isometric contraction following eccentric exercise of the elbow flexors between young, middle-aged, and old subjects. Ten young (20 +/- 2.0 years), 12 middle-aged (48 +/- 7.3 years), and 10 old (71 +/- 4.1 years) men performed six sets of five eccentric actions of the elbow flexors using a dumbbell weighing 40% of maximal voluntary isometric contraction strength (MVC) at an elbow joint angle of 90 degrees (1.57 rad). MVC was measured before, immediately after, and 1-5 days following exercise, and the force fluctuations were assessed at 30, 50, and 80% of the corresponding time point MVC using coefficient of variation (CV) of force data collected at a frequency of 100 Hz for 4 s. Changes in MVC and CV over time were compared between groups by a two-way repeated measures ANOVA. Changes in MVC following exercise were not significantly different between the young and middle-aged groups, but the old group showed significantly (P < 0.05) smaller decreases in MVC compared with other groups. CV increased significantly (P < 0.05) only immediately after exercise without a significant difference among the three intensities, and no significant differences between groups were evident. It was concluded that force fluctuations during submaximal isometric tasks after eccentric exercise were not affected by age.

Responses of old men to repeated bouts of eccentric exercise of the elbow flexors in comparison with young men

A bout of eccentric exercise confers protection against subsequent bouts of the same exercise. This study investigated whether the protective effect would be produced similarly between old and young adults. Eight old men (70.5 +/- 4.1 years) and ten young men (20.4 +/- 2.0 years) performed two bouts of eccentric exercise of the elbow flexors (six sets of five eccentric actions) separated by 4 weeks. Changes in maximal isometric strength, range of motion (ROM), upper arm circumference (CIR), plasma creatine kinase (CK) activity, myoglobin (Mb) concentration, and muscle soreness (SOR) before, immediately after, and 1, 24, 48, 72 and 96 h following exercise were compared between bouts, and between groups by a two-way repeated measures ANOVA. Changes in the measures following the first bout were significantly (P < 0.05) smaller for the old than the young group. The young group showed significantly (P < 0.05) smaller changes in all measures following the second bout than the first bout; however, the old group had the protective effect only for ROM, Mb, and SOR. The magnitude of the effect observed for ROM and Mb concentration in the old group was significantly (P < 0.05) smaller compared with that of the young group. These results suggest that the protective effect conferred by the first bout was less for the old than the young group. This may be due to the less muscle damage after the first bout in the old subjects, but it is also possible that the protective effect of old adults does not last as long as that of young adults.