Submaximal Eccentric Exercise Research Articles

Immediate crossover fatigue after unilateral submaximal eccentric contractions of the knee flexors involves peripheral alterations and increased global perceived fatigue.

After a unilateral muscle exercise, the performance of the non-exercised contralateral limb muscle can be also impaired. This crossover fatigue phenomenon is still debated in the literature and very few studies have investigated the influence of eccentric contractions. This study was designed to assess neuromuscular adaptations involved in the crossover fatigue of the non-exercised contralateral knee flexor muscles. Seventeen healthy young men performed a unilateral submaximal eccentric exercise of the right knee flexors until a 20% reduction in maximal voluntary isometric contraction torque was attained in the exercised limb. Before (PRE), immediately after exercise cessation (POST) and 24 hours later (POST24), neuromuscular function and perceived muscle soreness were measured in both the exercised limb and non-exercised limb. In addition, global perceived fatigue was assessed at each measurement time. At POST, significant reductions in maximal voluntary isometric contraction were observed in the exercised limb (-28.1%, p < 0.001) and in the non-exercised limb (-8.5%, p < 0.05), evidencing crossover fatigue. At POST, voluntary activation decreased in the exercised limb only (-6.0%, p < 0.001), while electrically evoked potentiated doublet torque was impaired in both the exercised limb and the non-exercised limb (-11.6%, p = 0.001). In addition, global perceived fatigue significantly increased at POST (p < 0.001). At POST24, all measured variables returned to PRE values, except for perceived muscle soreness scores exhibiting greater values than PRE (p < 0.05). A possible cumulative interaction between peripheral alterations and global perceived fatigue may account for the immediate crossover fatigue observed in the non-exercised limb.

Reliability and Variability of Lower Limb Muscle Activation as Indicators of Familiarity to Submaximal Eccentric Cycling.

Submaximal eccentric (ECC) cycling exercise is commonly used in research studies. No previous study has specified the required time naïve participants take to familiarize with submaximal ECC cycling. Therefore, we designed this study to determine whether critical indicators of cycling reliability and variability stabilize during 15 min of submaximal, semi-recumbent ECC cycling (ECC cycling). Twenty-two participants, aged between 18–51 years, volunteered to complete a single experimental session. Each participant completed three peak eccentric torque protocol (PETP) tests, nine countermovement jumps and 15 min of submaximal (i.e., 10% peak power output produced during the PETP tests) ECC cycling. Muscle activation patterns were recorded from six muscles (rectus femoris, RF; vastus lateralis, VL; vastus medialis, VM; soleus, SOL; medial gastrocnemius, GM; tibialis anterior, TA), during prescribed-intensity ECC cycling, using electromyography (EMG). Minute-to-minute changes in the reliability and variability of EMG patterns were examined using intra-class correlation coefficient (ICC) and variance ratios (VR). Differences between target and actual power output were also used as an indicator of familiarization. Activation patterns for 4/6 muscles (RF, VL, VM and GM) became more consistent over the session, the RF, VL and VM increasing from moderate (ICC = 0.5–0.75) to good (ICC = 0.75–0.9) reliability by the 11th minute of cycling and the GM good reliability from the 1st minute (ICC = 0.79, ICC range = 0.70–0.88). Low variability (VR ≤ 0.40) was maintained for VL, VM and GM from the 8th, 8th and 1st minutes, respectively. We also observed a significant decrease in the difference between actual and target power output (χ2 14 = 30.895, p = 0.006, W = 0.105), expressed primarily between the 2nd and 3rd minute of cycling (Z = -2.677, p = 0.007). Indicators of familiarization during ECC cycling, including deviations from target power output levels and the reliability and variability of muscle activation patterns stabilized within 15 min of cycling. Based upon this data, it would be reasonable for future studies to allocate ∼ 15 min to familiarize naïve participants with a submaximal ECC cycling protocol.

Tolerance to submaximal eccentric exercise in women with and without fibromyalgia, moving away from anecdotal beliefs

We have shown people with fibromyalgia experience exacerbated pain in the exercising limb up to three days following submaximal isometric and concentric exercise however, the pain response following eccentric exercise has not been investigated. This study investigated the change in experimental pain up to two days following submaximal eccentric exercise while clinical pain was assessed through the 7-day recovery period in women with and without FM. Eighteen women with fibromyalgia (49.1±11.8yr, BMI: 31.4±7.6) and 18 controls (49.5±10.1yr, BMI: 27.1±4.8) completed session 1 (exercise) and session 2 (recovery assessment) separated by 2 days; session 1 included a 10-minute bout of submaximal (20% of maximal voluntary contraction) eccentric exercise with the right elbow flexors. Pressure pain thresholds (PPTs), mechanical pain summation, and punctate pain summation were assessed before, immediately after exercise, and in session 2. Clinical pain (0-10 NRS) in the exercising arm and whole-body was assessed before, during, immediately after, and up to seven days following the exercise bout. PPTs and mechanical pain summation did not change immediately following exercise or session 2 (Time, p>0.05). Punctate pain summation changed following exercise (Time x Summation, p=0.003) however, post hoc analysis did not reveal a significant difference immediately after exercise (p=0.296) or at session two (p=0.03). The fibromyalgia group reported greater increases in exercising arm pain during (Time x Group, p

Effects of Submaximal Eccentric Exercise on Muscle Activity at Different Elbow Joint Angles

Our study aimed to determine whether electrical and mechanical factors contributing to acute or long-term maximal torque reduction and muscle soreness due to submaximal eccentric exercise (ECC) are elbow-joint-angle specific and to what extent the joint angle affects the contribution of antagonist coactivation to this torque reduction. Maximal isometric torque (MIT), muscle soreness assessment, agonist electromechanical activities, and antagonist coactivation during the maximal voluntary contraction (MVC) were measured at elbow joint angles of 60°, 90°, and 150° before ECC, immediately after exercise, and 24, 48, 72, and 120 hr after exercise. ECC causes an immediate decrease in MIT as well as increased antagonist coactivation at three angles. Antagonist coactivation returned to its baseline level at 24 hr regardless of joint angle. The most rapid torque recovery and the highest force level at which pain occurred were found after ECC at a joint angle of 60°. During the recovery period, no mechanomyographical changes were observed when measuring surface mechanomyography changes at three angles, while the electrical activity differed between angles.

Potent Protective Effect Conferred by Four Bouts of Low-Intensity Eccentric Exercise

It is known that submaximal eccentric exercise does not confer as strong a protective effect as maximal eccentric exercise. This study tested the hypothesis that four bouts of submaximal eccentric exercise would confer a similar protective effect to one bout maximal eccentric exercise. Thirty untrained men were placed into 4 x 40% (40%) or control (CON) groups (n = 15 per group) by matching preexercise maximal voluntary isometric contraction strength (MVC). The 40% group performed 30 eccentric contractions with a load of 40% MVC (40% ECC) every 2 wk for four times followed 2 wk later by 30 maximal eccentric exercise (100% ECC) of the elbow flexors of the nondominant arm. The CON group performed two bouts of the 100% ECC separated by 2 wk. MVC at six angles, optimum angle (OA), concentric isokinetic strength (30 degrees x s(-1) and 300 degrees x s(-1)), range of motion, upper arm circumference, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo intensity of B-mode ultrasound images were taken before to 5 d after each exercise. No significant differences in the changes in any measures were evident between the 100% ECC of the 40% group and the second 100% ECC of the CON group. Changes in all measures except for OA and upper arm circumference after the second to the fourth 40% ECC bouts were significantly smaller than those after the first 40% ECC bout. The changes in the measures after any of the 40% ECC bouts were significantly (P < 0.05) smaller than those after the first 100% ECC bout of the CON group. These results suggest that repeating submaximal eccentric exercise confers the same magnitude of protective effect as one bout of maximal eccentric exercise against the subsequent maximal eccentric exercise.

Counterpoint: Estrogen and Sex do not Significantly Influence Post-Exercise Indexes of Muscle Damage, Inflammation, and Repair

Exercise-induced muscle damage (EIMD) occurs following strenuous, novel exercise and is assessed directly via tissue analysis and characterized indirectly by muscle dysfunction, inflammation, delayed onset muscle soreness, and increased levels of muscle proteins [e.g., creatine kinase (CK),

Shift of Peak Torque Angle After Eccentric Exercise

This study aims to investigate the changes in the mechanical properties of quadriceps muscle following a sub-maximal concentric-eccentric stepping exercise protocol. Twenty-four untrained healthy subjects aged 21.9 +/- 0.55 years were asked to perform a 10-minute stepping exercise where the dominant leg worked eccentrically and the non-dominant leg worked concentrically at a rate of 15 cycles/min. The quadriceps isokinetic peak torque and the corresponding peak torque angle at angular velocity of 60 degrees /sec, and muscle soreness were determined at baseline, immediately after, day 1 and day 2 after the exercise protocol. Repeated measures of ANOVA showed no change in the peak torque after the eccentric exercise and concentric exercise (p > 0.05). There was a significant shift in the peak torque angle to longer muscle lengths in the eccentrically-exercised leg immediately (65.6 +/- 2.21 degrees ) and on the following two days after exercise (day 1: 68.3 +/- 2.71 degrees ; day 2: 67.4 +/- 2.51 degrees ) when compared with baseline (61.4 +/- 1.55 degrees , p < 0.05). These features were not observed in the concentrically-exercised leg. Eccentric exercise produced a higher level of soreness than concentric exercise at day 1 and 2 after the protocol. Submaximal eccentric exercise could bring about changes in the muscle properties resulting in a shift in the angle-torque relationship to longer muscle length without significant force deficit.

Maximal lengthening contractions increase p70 S6 kinase phosphorylation in human skeletal muscle in the absence of nutritional supply

The aim of this study was to compare the training stimuli of eccentric (lengthening) and concentric (shortening) contractions regarding the effect on signaling enzymes involved in protein synthesis. Ten male subjects performed 4 x 6 maximal eccentric contractions on one leg followed by 4 x 6 maximal concentric contractions on the other. Six additional subjects performed the same protocol, but with maximal concentric and submaximal eccentric exercise of equal force to that of the maximal concentric contractions. Muscle biopsy samples were taken from the vastus lateralis before, immediately after, and 1 and 2 h after exercise in both legs. The average peak force produced during the maximal eccentric exercise was 31% higher than during the maximal concentric exercise, 2,490 (+/-100) vs. 1,894 (+/-108) N (P < 0.05). The maximal eccentric contractions led to two- to eightfold increases in the phosphorylation of p70 S6 kinase (p70(S6k)) and the ribosomal protein S6 that persisted for 2 h into recovery but no significant changes in phosphorylation of Akt or mammalian target of rapamycin (mTOR). Maximal concentric and submaximal eccentric contractions did not induce any significant changes in Akt, mTOR, p70(S6k), or S6 phosphorylation up to 2 h after the exercise. The results indicate that one session of maximal eccentric contractions activates p70(S6k) in human muscle via an Akt-independent pathway and suggest that maximal eccentric contractions are more effective than maximal concentric contractions in stimulating protein synthesis in the absence of a nutritional intake, an effect that may be mediated through a combination of greater tension and stretching of the muscle.

The magnitude of muscle damage induced by downhill backward walking

While various models for exercise-induced muscle damage (EIMD) have been introduced, many of them use maximal voluntary contractions of the elbow flexors and knee extensors performed on isokinetic dynamometers. Few studies have used exercise protocols that attempt to replicate submaximal eccentric muscle actions that commonly occur during daily activities. Downhill backwards walking has been used previously as an EIMD model. However, the common markers of muscle damage have not been systematically examined for this model. The purpose of this study was to determine the magnitude of muscle damage induced by downhill backward walking with regard to changes in commonly-used indirect markers of EIMD. Twenty subjects aged between 19 y and 42 y completed a bout of 60 min of downhill (-15%) backward walking in which a single limb performed submaximal eccentric actions at a stepping rate of 30 - 35 strides per min. A repeated measures ANOVA revealed significant (p < 0.05) increases from baseline for soreness (24 hr- 96 hr), tenderness (24 hr - 96 hr), and plasma creatine kinase activity (0.5 hr - 96 hr), and significant decreases (p < 0.05) in maximal voluntary isometric (approximately 25%) and isokinetic (-15%) strength (0.5 hr - 96 hr) post-walk for the exercised limb. The time course of observed changes in these markers was similar to that reported for EIMD models of the elbow flexors and knee extensors. However, the magnitude of muscle damage appeared more consistent with that demonstrated following submaximal eccentric exercise.

Comparison between leg and arm eccentric exercises of the same relative intensity on indices of muscle damage

Many exercise models have demonstrated associations between eccentric muscle actions and muscle damage. However, the magnitude of muscle damage varies among the models. It appears that responses to eccentric exercise are different between leg and arm muscles but this has not been systematically clarified. This study compared leg and arm eccentric exercises of the same relative intensity for indices of muscle damage. Eleven healthy untrained males [Age: 21.2 (1.0) years, Height: 179.4 (3.0) cm, Weight: 78.4 (3.1) kg] performed a sub-maximal eccentric exercise of the knee extensors (LEGS) and the elbow flexors (ARMS), separately. Both LEGS and ARMS consisted of six sets of 12 repetitions with an intensity corresponding to 75% of the predetermined maximal eccentric peak torque (EPT) of each muscle. Range of motion (ROM), delayed onset muscle soreness (DOMS), serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities, myoglobin (Mb) concentration, and muscle strength [EPT and isometric peak torque (IPT)] were assessed before and 24, 48, 72, and 96 h following exercise. Significant (P < 0.05) changes in DOMS and ROM were observed up to 96 h after both exercise bouts, and the magnitude of the change was similar between LEGS and ARMS. Increases in CK and Mb were significantly (P < 0.05) larger after ARMS than LEGS at 72 and 96 h post-exercise. EPT and IPT were significantly (P < 0.05) lower than the baseline up to 96 h post-exercise for ARMS but were fully recovered by 96 h post-exercise for LEGS. Decreases in muscle strength were significantly (p < 0.05) larger following ARMS than LEGS at 48, 72, and 96 h post-exercise for EPT, and from 24 h to 96 h post-exercise for IPT. These results suggest that the magnitude of muscle damage is greater and the recovery of muscle function was slower after eccentric exercise of arm elbow flexors than the knee extensors.

Delayed onset muscle soreness induced by eccentric isokinetic exercise

Delayed onset muscle soreness (DOMS) follows unaccustomed muscular exercise, most notably in the eccentric mode. That concept refers to a dull ache combined with tenderness, stiffness and weakness of the previously activemuscles. Isokinetic device constitutes a specific model in generating and investigating DOMS. Respective effects of concentric and eccentric actions have been compared, emphasizing on the variability in the response (serum activity of CK for instance). The particular sensitivity of the hamstrings was underlined although causes remained unexplained. Some treatment have been proposed in the management of DOMS. Several studies reported that anti-inflammatory agents fail to alleviate pain and discomfort even if other authors indicated a relative effectiveness. Based on the repeated-bout effect, submaximal eccentric exercise currently represent the most useful preventive strategy.

Proprioceptive and reflex responses of triceps surae to submaximal eccentric exercise

Proprioceptive and reflex responses of triceps surae to submaximal eccentric exercise

Difference in the Magnitude of Muscle Damage Between Maximal and Submaximal Eccentric Loading

This study compared maximal (MAX-ECC) and submaximal (50%-ECC) eccentric exercise of the elbow flexors. Untrained male students (n = 8) performed 3 sets of 10 repetitions of MAX-ECC with one arm and 50%-ECC with the other arm, separated by 4 weeks. In MAX-ECC, the elbow joint was forcibly extended from a flexed (90 degrees ) to a full-extended position (180 degrees ) in 3 seconds while producing maximal force. For 50%-ECC, a dumbbell set at 50% of the maximal isometric strength at 90 degrees of the elbow joint was lowered from the flexed to the extended position in 3 seconds. Changes in indicators of muscle damage were compared between the bouts by a 2-way repeated-measures analysis of variance. Changes in isometric strength, range of motion, upper arm circumference, and plasma creatine kinase activity were significantly smaller and the recovery was significantly faster for 50%-ECC compared with MAX-ECC, although the differences in the changes immediately after exercise were small. It appeared that the magnitude of initial muscle damage was similar between the bouts; however, secondary damage was less after 50%-ECC.

Cardiovascular Responses to Submaximal Concentric and Eccentric Isokinetic Exercise in Older Adults

Our purpose was to describe heart rate (HR), mean arterial blood pressure (MAP), and perceived exertion (RPE) responses to submaximal isokinetic concentric (CON) and eccentric (ECC) exercise at the same absolute torque output in older adults. Peak torques for ECC and CON knee extension were determined in healthy older males (n = 13) and females (n = 7). Subjects then performed separate, randomly ordered, 2-min bouts of CON and ECC exercise. Heart rate and MAP increased (p &lt; .001) from resting values throughout both exercise bouts. CON exercise elicited a significantly greater cardiovascular response than ECC exercise after 60 s. Peak HR, MAP, and RPE after CON exercise were greater than after ECC exercise (p &lt; .01). At the same absolute torque output, isokinetic CON knee extension exercise resulted in a significantly greater level of cardiovascular stress than ECC exercise. These results are relevant to resistance testing and exercise in older people.

Prolonged submaximal eccentric exercise is associated with increased levels of plasma IL-6.

To study the relationship between exercise-related muscle proteolysis and the cytokine response, a prolonged eccentric exercise model of one leg was used. Subjects performed two trials [a branched-chain amino acid (BCAA) supplementation and a control trial]. The release of amino acids from muscle during and after the eccentric exercise was decreased in the BCAA trial, suggesting a suppression of net muscle protein degradation. The plasma concentrations of interleukin (IL)-6 increased from 0.75 +/- 0.19 (preexercise) to 5.02 +/- 0.96 pg/ml (2 h postexercise) in the control trial and in the BCAA supplementation trial from 1.07 +/- 0.41 to 4.15 +/- 1.21 pg/ml. Eccentric exercise had no effect on the concentrations of neutrophils, lymphocytes, CD16+/CD56+, CD4+, CD8+, CD14+/CD38+, lymphocyte proliferative response, or cytotoxic activities. BCAA supplementation reduced the concentration of CD14+/CD38+ cells. This study shows that the concentration of IL-6 in plasma is increased after prolonged eccentric exercise and suggests that the cytokine response is independent of the muscle proteolysis that occur during exercise.

Creatine kinase isoenzyme MB may be elevated in healthy young women after submaximal eccentric exercise.

Elevations in serum creatine kinase isoenzyme MB (CK MB) after exercise may be of clinical importance for the diagnosis of myocardial infarction. However, CK MB has been observed to increase after exercise in highly trained endurance runners. No data exist relating to the effect of exercise in a heterogeneous female population with regard to CK MB. The purpose of the present investigation was to determine whether an elevation in serum CK MB can be measured in women (heterogeneous for aerobic capacity, estradiol, and lean body mass) and to make a preliminary analysis of the relationships of postexercise serum CK MB concentration and CK activity, estradiol, lean body mass, and peak oxygen consumption. Lean body mass and peak oxygen consumption were measured for 15 college-age women (19 to 29 years) after the performance of a stepping exercise for 40 minutes at 70% of peak oxygen consumption to elicit the efflux of intramuscular enzymes. Serum CK MB concentration, CK activity, and estradiol level were measured before exercise and 24 and 48 hours after exercise. Serum estradiol level was also measured immediately after exercise. Four of the 15 subjects had elevations in CK MB concentrations ranging from 18.4 to 101.2 micrograms/L, many times the upper normal limit (4.7 micrograms/L). All subjects with high serum CK MB concentrations had high CK activity, and the two measures were significantly related (p < 0.01) in the postexercise period. It was concluded that exercise can cause large elevations in serum CK MB in some women.(ABSTRACT TRUNCATED AT 250 WORDS)