High-intensity Eccentric Contractions Research Articles

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

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. 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 72hr) in Bout 1 and 14days 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 7min (126 steps per limb). Two-way repeated measures ANOVAs were conducted to identify any significant effects (P ≤ 0.05). Eccentric strength significantly decreased (-13%) in Bout 1 at 24hr 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. Submaximal multi-joint eccentric exercise results in minimal disruption to neuromuscular function associated with falls in older adults after the initial bout.

Power loss is attenuated following a second bout of high-intensity eccentric contractions due to the repeated bout effect's protection of rate of torque and velocity development.

High-intensity unaccustomed eccentric contractions result in weakness and power loss because of fatigue and muscle damage. Through the repeated bout effect (RBE), adaptations occur, then damage and weakness are attenuated following a subsequent bout. However, it is unclear whether the RBE protects peak power output. We investigated the influence of the RBE on power production and estimated fatigue- and damage-induced neuromuscular impairments following repeated high-intensity eccentric contractions. Twelve healthy adult males performed 5 sets of 30 maximal eccentric elbow flexions and repeated an identical bout 4 weeks later. Recovery was tracked over 7 days following both bouts. Reduced maximum voluntary isometric contraction torque, and increased serum creatine kinase and self-reported soreness indirectly inferred muscle damage. Peak isotonic power, time-dependent measures- rate of velocity development (RVD) and rate of torque development (RTD)- and several electrophysiological indices of neuromuscular function were assessed. The RBE protected peak power, with a protective index of 66% 24 h after the second eccentric exercise bout. The protection of power also related to preserved RVD (R2 = 0.61, P < 0.01) and RTD (R2 = 0.39, P < 0.01). Furthermore, the RBE's protection against muscle damage permitted the estimation of fatigue-associated neuromuscular performance decrements following eccentric exercise. Novelty: The repeated bout effect protects peak isotonic power. Protection of peak power relates to preserved rates of torque and velocity development, but more so rate of velocity development. The repeated bout effect has little influence on indices of neuromuscular fatigue.

Damage protective effects conferred by low-intensity eccentric contractions on arm, leg and trunk muscles.

Low-intensity eccentric contractions with a load corresponding to 10% of maximal voluntary isometric contraction strength (10% EC) attenuate muscle damage in a subsequent bout of higher-intensity eccentric contractions performed within 2 weeks for the elbow flexors, knee flexors and knee extensors. However, it is not known whether this strategy could be applied to other muscles. This study investigated whether 10% EC would confer damage protective effect on high-intensity eccentric contractions (80% EC) for nine different muscle groups. Untrained young men were placed to an experimental or a control group (n = 12/group). Experimental group performed 50 eccentric contractions with a load corresponding to 10% EC at 2 days prior to 50 eccentric contractions with 80% EC for the elbow flexors and extensors, pectoralis, knee flexors and extensors, plantar flexors, latissimus, abdominis and erector spinae. Control group performed 80% EC without 10% EC. Changes in maximal voluntary isometric contraction strength (MVC) and muscle soreness, plasma creatine kinase (CK) activity and myoglobin concentration after 80% EC were compared between groups by a mixed-factor ANOVA. MVC recovered faster (e.g., 6-31% greater MVC at 5 days post-exercise), and peak muscle soreness was 36-54% lower for Experimental than Control group for the nine muscles (P < 0.05). Increases in plasma CK activity and myoglobin concentration were smaller for Experimental (e.g., peak CK: 2763 ± 3459IU/L) than Control group (120,360 ± 50,158IU/L). These results showed that 10% EC was effective for attenuating the magnitude of muscle damage after 80% EC for all muscles, although the magnitude of the protective effect differed among the muscles.

Prevention of downhill walking-induced muscle damage by non-damaging downhill walking.

PurposeMountain trekking involves level, uphill, and downhill walking (DW). Prolonged DW induces damage to leg muscles, reducing force generating ability and muscle coordination. These increase risks for more serious injuries and accidents in mountain trekking, thus a strategy to minimize muscle damage is warranted. It has been shown that low-intensity eccentric contractions confer protective effect on muscle damage induced by high-intensity eccentric contractions. This study tested the hypothesis that 5-min non-damaging DW would attenuate muscle damage induced by 40-min DW, but 5-min level walking (LW) would not.MethodsUntrained young men were allocated (n = 12/group) to either a control or one of the two preconditioning groups (PRE-DW or PRE-LW). The PRE-DW and PRE-LW groups performed 5-min DW (-28%) and 5-min LW, respectively, at 5 km/h with a load of 10% body mass, 1 week before 40-min DW (-28%, 5 km/h, 10% load). The control group performed 40-min DW only. Maximal knee extension strength, plasma creatine kinase (CK) activity, and muscle soreness (0–100 mm visual analogue scale) were measured before and 24 h after 5-min DW and 5-min LW, and before and 24, 48, and 72 h after 40-min DW.ResultsNo significant changes in any variables were evident after 5-min DW and 5-min LW. After 40-min DW, the control and PRE-LW groups showed significant (P<0.05) changes in the variables without significant differences between groups (control vs. PRE-LW; peak strength reduction: -19.2 ± 6.9% vs. -18.7 ± 11.0%, peak CK: 635.5 ± 306.0 vs. 639.6 ± 405.4 U/L, peak soreness: 81.4 ± 14.8 vs. 72.0 ± 29.2 mm). These changes were significantly (P<0.05) attenuated (47–64%) for the PRE-DW group (-9.9 ± 9.6%, 339.3 ± 148.4 U/L, 27.8 ± 16.8 mm).ConclusionsThe results supported the hypothesis and suggest that performing small volume of downhill walking is crucial in preparation for trekking.

Photobiomodulation therapy (PBMT) and/or cryotherapy in skeletal muscle restitution, what is better? A randomized, double-blinded, placebo-controlled clinical trial.

Cryotherapy for post-exercise recovery remains widely used despite the lack of quality evidence. Photobiomodulation therapy (PBMT) studies (with both low-level laser therapy and light-emitting diode therapy) have demonstrated positive scientific evidence to suggest its use. The study aims to evaluate PBMT and cryotherapy as a single or combined treatment on skeletal muscle recovery after eccentric contractions of knee extensors. Fifty healthy male volunteers were recruited and randomized into five groups (PBMT, cryotherapy, cryotherapy + PBMT, PMBT + cryotherapy, or placebo) for a randomized, double-blinded, placebo-controlled trial that evaluated exercise performance (maximum voluntary contraction (MVC)), delayed onset muscle soreness (DOMS), and muscle damage (creatine kinase (CK)). Assessments were performed at baseline; immediately after; and at 1, 24, 48, 72, and 96h. Comparator treatments was performed 3min after exercise and repeated at 24, 48, and 72h. PBMT was applied employing a cordless, portable GameDay™ device (combination of 905nm super-pulsed laser and 875- and 640-nm light-emitting diodes (LEDs); manufactured byMulti Radiance Medical™, Solon - OH, USA), and cryotherapy by flexible rubber ice packs. PBMT alone was optimal for post-exercise recovery with improved MVC, decreased DOMS, and CK activity (p < 0.05) from 24 to 96h compared to placebo, cryotherapy, and cryotherapy + PBMT. In the PBMT + cryotherapy group, the effect of PBMT was decreased (p > 0.05) but demonstrated significant improvement in MVC, decreased DOMS, and CK activity (p < 0.05). Cryotherapy as single treatment and cryotherapy + PBMT were similar to placebo (p > 0.05). We conclude that PBMT used as single treatment is the best modality for enhancement of post-exercise restitution, leading to complete recovery to baseline levels from 24h after high-intensity eccentric contractions.

Precipitation Of Muscle Damage In Females Following A Sport-specific Bout Of Repeated Sprints

High intensity eccentric contractions can result in exercise-induced muscle damage (EIMD), the symptoms of which are temporary, but last for several days following the initial bout. Although the responses have been well described in the literature, there is a paucity of data surrounding this response in females. PURPOSE: The aim of this study was to examine the damage responses from a sport-specific bout of repeated sprints on well-trained collegiate female athletes. METHODS: Eleven well-trained females (mean ± SD; age 22 ± 3 y, height 166.6 ± 5.7 cm, mass 62.7 ± 4.5 kg) took part in a repeated sprint protocol designed to induce EIMD (15 by 30 m sprints, with an enforced deceleration, and a 60 s rest period between repetitions). Markers of EIMD were assessed before and up to 72 hours following the repeated sprint protocol. These included creatine kinase (CK), jump height (CMJ), maximum voluntary contractions (MVC), sprint times, limb girth and muscle soreness (DOMS). All participants were tested throughout the luteal phase of the menstrual cycle. RESULTS: CK was elevated at 24, 48 and 72 h (p≤0.035), peaking at 24 h (+418%) and returning towards baseline at 72 h. CMJ significantly reduced immediately post, 24 and 48 h (p<0.05) post exercise, with a mean jump height decline of 12% from pre exercise (26.4 ± 3.3 cm) to immediately post exercise (23.4 ± 4 cm). Sprint performance was also negatively affected immediately post, 24 h, 48 h and 72 h post exercise, nadir at 48 h (5.25 ± 0.4 s) equating to a 6 % increase from pre exercise times. Muscle soreness peaked at 48 h (p<0.001) and stayed significantly elevated at 72 h post exercise (p<0.003). Limb girth or MVC did not alter over time. CONCLUSIONS: The current study demonstrates that a sport specific bout of repeated sprints precipitates EIMD in trained females and has the potential to negatively affect performance in the subsequent days, which is evidenced by decrements in muscle function and soreness. Further research is needed to examine the damage responses in this population following other damaging exercise paradigms, and importantly if the menstrual cycle influences the EIMD response.

Soil properties, bacterial community composition, and metabolic diversity responses to soil salinization of a semiarid grassland in northeast China

High-intensity eccentric contractions induce performance decrements and delayed onset muscle soreness. The purpose of this investigation was to study the magnitude and time course of such decrements and their interrelationships in 26 young women of mean(s.d.) age 21.4(3.3) years. Subjects performed 70 maximal eccentric contractions of the elbow flexors on a pulley system, specially designed for the study. The non-exercised arm acted as the control. Measures of soreness, tenderness, swelling (SW), relaxed elbow joint angle (RANG) and isometric strength (STR) were taken before exercise, immediately after exercise (AE), analysis of variance and at 24-h intervals for 11 days. There were significant (P &lt; 0.01, analysis of variance) changes in all factors. Peak effects were observed between 24 and 96 h AE. With the exception of STR, which remained lower (P &lt; 0.01), all variables returned to baseline levels by day 11. A non-significant correlation between pain and STR indicated that pain was not a major factor in strength loss. Also, although no pain was evident, RANG was decreased immediately AE. There was no relationship between SW, RANG and pain. The prolonged nature of these symptoms indicates that repair to damaged soft tissue is a slow process. Strength loss is considered particularly important as it continues when protective pain and tenderness have disappeared. This has implications for the therapeutic management of patients with myopathologies and those receiving eccentric exercise for rehabilitation.

Linear and nonlinear analyses of multi-channel mechanomyographic recordings reveal heterogeneous activation of wrist extensors in presence of delayed onset muscle soreness

In this study, we applied multi-channel mechanomyographic (MMG) recordings in combination with linear and nonlinear analyses to investigate muscular and musculotendinous effects of high intensity eccentric exercise. Twelve accelerometers arranged in a 3×4 matrix over the dominant elbow muscles were used to detect MMG activity in 12 healthy participants. Delayed onset muscle soreness was induced by repetitive high intensity eccentric contractions of the wrist extensor muscles. Average rectified values (ARV) as well as percentage of recurrence (%REC) and percentage of determinism (%DET) extracted from recurrence quantification analysis were computed from data obtained during static–dynamic contractions performed before exercise, immediately after exercise, and in presence of muscle soreness. A linear mixed model was used for the statistical analysis. The ARV, %REC, and %DET maps revealed heterogeneous MMG activity over the wrist extensor muscles before, immediately after, and in presence of muscle soreness (P<0.01). The ARVs were higher while the %REC and %DET were lower in presence of muscle soreness compared with before exercise (P<0.05). The study provides new key information on linear and nonlinear analyses of multi-channel MMG recordings of the wrist extensor muscles following eccentric exercise that results in muscle soreness. Recurrence quantification analysis can be suggested as a tool for detection of MMG changes in presence of muscle soreness.

Black Currant Nectar Reduces Muscle Damage and Inflammation Following a Bout of High-Intensity Eccentric Contractions

ABSTRACTThis investigation determined the efficacy of black currant nectar (BCN) in reducing symptoms of exercise-induced muscle damage (EIMD). Sixteen college students were randomly assigned to drink either 16 oz of BCN or a placebo (PLA) twice a day for eight consecutive days. A bout of eccentric knee extensions (3 × 10 sets @ 115% of 1RM) was performed on the fourth day. Outcome measures included muscle soreness (subjective scale from 0 to 10) and blood markers of muscle damage (creatine kinase, CK), inflammation (interleukin-6, IL-6), and oxygen radical absorbance capacity (ORAC). Although there were no differences in reported soreness between groups, consumption of BCN reduced CK levels at both 48 (PLA = 82.13% vs. BCN = −6.71%, p = .042) and 96 h post exercise (PLA = 74.96% vs. BCN = −12.11%, p = .030). The change in IL-6 was higher in the PLA group (PLA = 8.84% vs. BCN = −6.54%, p = .023) at 24 h post exercise. The change in ORAC levels was higher in the treatment group (BCN = 2.68% vs. PLA = −6.02%, p = .039) at 48 h post exercise. Our results demonstrate that consumption of BCN prior to and after a bout of eccentric exercise attenuates muscle damage and inflammation.

Creatine kinase, myosin heavy chains and magnetic resonance imaging after eccentric exercise

The aim of this study was to examine the relationship between myosin heavy chain (MHC) release as a specific marker of slow-twitch muscle fibre breakdown and magnetic resonance imaging (MRI) of skeletal muscle injury after eccentric exercise. The effects of a single series of 70 high-intensity eccentric contractions of the quadriceps femoris muscle group (single leg) on plasma concentrations of creatine kinase and MHC fragments were assessed in 10 young male sport education trainees before and 1 and 4 days after exercise. To visualize muscle injury, MRI of the loaded thigh was performed before and 4 days after the eccentric exercise. All participants recorded an increase ( P ≪ 0.05) in creatine kinase after exercise. In five participants, T2 signal intensity was unchanged post-exercise compared with pre-exercise and MHC plasma concentration was normal; however, they showed an increase ( P ≪ 0.05) in creatine kinase after exercise. For the remaining five participants, there was an increase in T2 signal intensity of the loaded vastus intermedius and vastus lateralis. These changes in MRI were accompanied by an increase in MHC plasma concentration ( P ≪ 0.01) as well as an increase in creatine kinase ( P ≪ 0.01). We suggest that changes in MRI T2 signal intensity after muscle damage induced by eccentric exercise are closely related to damage to structurally bound contractile filaments of some muscle fibres. Additionally, MHC plasma release indicates that this damage affects not only fast-twitch fibres but also some slow-twitch fibres.

Can exercise-induced muscle damage be avoided?

All athletes have experienced the discomfort and debilitating effects of exercise-induced muscle damage. Symptoms are most common at the beginning of the season when intense training is reintroduced after a period of relative inactivity. A plethora of scientific data describes exercise conditions that lead to muscle damage. It is well accepted that damage occurs with unfamiliar exercise, primarily involving eccentric contractions. For example, downhill running places a large eccentric stress on the quadriceps muscle group and commonly results in muscle damage.1 However, muscles that have been preconditioned with eccentric contractions are protected against damage from subsequent bouts of eccentric exercise. This muscle damage is known as the “repeated-bout effect” and has been shown with various forms of exercise in both humans and animal models.2 Despite the many studies describing muscle damage and its various clinical symptoms, few have identified intrinsic causative factors or suitable interventions for limiting the symptoms. Clinically, it is important to first identify people at risk of developing more severe symptoms and then to design interventions that might limit those symptoms. Three recent experimental studies provide clinically relevant information for athletes and physicians.3,4,5 Controlled experimental studies have shown wide variation in symptoms between subjects after a bout of unfamiliar eccentric exercise. These data indicate that some people are more susceptible to damage than others, but it is not clear why. Recently musculoskeletal flexibility has been shown to be an important factor affecting the severity of symptoms after eccentric exercise.3 Flexibility was quantified according to a measure of passive muscle stiffness, and subjects' muscles were categorized as “stiff,” “normal,” or “compliant.” After a bout of eccentric exercise, subjects with stiff muscles had significantly greater loss of strength, pain, muscle tenderness, and elevation of plasma creatine kinase activity than those with compliant muscles. Greater apparent muscle damage was attributed to the inability of the tendon and aponeurosis of stiffer muscles to absorb the lengthening imposed by the eccentric contractions. Warm-up and stretching are known to greatly reduce muscle stiffness.6 Because stiffness seems to predispose muscles to damage, it follows that appropriately warming up before exercise may reduce the severity of exercise-induced muscle damage. It has also been shown that warm-up reduces subsequent symptoms of muscle damage.4 Eccentric contractions of the elbow flexors preceded by a warm-up resulted in significantly less loss of strength and elevation of plasma creatine kinase activity than eccentric contractions without a prior warm-up. The protective effect was attributed to decreased passive muscle stiffness, although actual stiffness measurements were not made. Besides the possible role of warm-ups in limiting the symptoms of muscle damage, preconditioning the muscle with eccentric contractions clearly provides a protective effect (repeated-bout effect). Recent data suggest that it may not be necessary to damage the muscle with the initial bout to provide a protective effect.5 Brown and associates showed that as few as 10 maximal eccentric contractions of the knee extensors were sufficient to reduce symptoms appreciably after a subsequent bout of 50 maximal contractions performed three weeks later. There was a clear repeated-bout effect despite that 10 contractions did not result in appreciable muscle damage. These data indicate that preconditioning muscles with a few maximal eccentric contractions can considerably reduce symptoms after a subsequent, more intense, bout of eccentric exercise. The key elements for the repeated-bout effect are that the preconditioning contractions are eccentric, that high-intensity contractions are performed, and that the preconditioning contractions affect the same muscle groups that will be working eccentrically in the repeated bout. All dynamic sports activities involve a large component of high-intensity eccentric contractions, whether the activity is in a game or a practice. Athletes typically experience considerable symptoms of muscle damage when returning to these activities after a prolonged layoff because of injury or between seasons. The severity of these symptoms may be reduced by maintaining good flexibility, especially of the principal muscle groups involved in the given sport; preconditioning the principal muscle groups with a few high-intensity eccentric contractions one to two weeks before returning to full activities; and performing specific warm-up exercises for the principal muscle groups immediately before the first few training sessions or games. Increasing the athletes' awareness of the cause of symptoms will increase compliance with any intervention directed at limiting muscle damage. This is especially important in sports that do not place a large emphasis on warm-up or flexibility.

Muscle soreness, swelling, stiffness and strength loss after intense eccentric exercise.

High-intensity eccentric contractions induce performance decrements and delayed onset muscle soreness. The purpose of this investigation was to study the magnitude and time course of such decrements and their interrelationships in 26 young women of mean(s.d.) age 21.4(3.3) years. Subjects performed 70 maximal eccentric contractions of the elbow flexors on a pulley system, specially designed for the study. The non-exercised arm acted as the control. Measures of soreness, tenderness, swelling (SW), relaxed elbow joint angle (RANG) and isometric strength (STR) were taken before exercise, immediately after exercise (AE), analysis of variance and at 24-h intervals for 11 days. There were significant (P < 0.01, analysis of variance) changes in all factors. Peak effects were observed between 24 and 96 h AE. With the exception of STR, which remained lower (P < 0.01), all variables returned to baseline levels by day 11. A non-significant correlation between pain and STR indicated that pain was not a major factor in strength loss. Also, although no pain was evident, RANG was decreased immediately AE. There was no relationship between SW, RANG and pain. The prolonged nature of these symptoms indicates that repair to damaged soft tissue is a slow process. Strength loss is considered particularly important as it continues when protective pain and tenderness have disappeared. This has implications for the therapeutic management of patients with myopathologies and those receiving eccentric exercise for rehabilitation.