Electromyographic analysis of the pectoralis major and deltoideus anterior in the inclined "flying" exercise with loads

Due to a shortage of textbooks with specific data on muscular activity concerning physical conditioning and sports, we analysed electromyographically the muscles pectoralis major and deltoideus anterior, bilaterally, in inclined "flying" exercises, during the concentric and eccentric phases, with external loads of 25, 50, 75 and 100% of the maximum load. The electromyographic analysis was performed in eleven male volunteers with MEDI-TRACE-200 surface electrodes connected to a six-channel biologic signal acquisition module coupled to a PC/AT computer. The electromyographic signals were processed and the obtained effective values were normalized through maximum voluntary isometric contraction. Statistically, the results showed that all the muscles studied presented significant differences between the concentric and the eccentric phases, with higher electromyographic activity during the concentric phase. By analysing the different loads for each muscle in both phases, significant electromyographic activity was observed for all muscles. When the effect of each load on each muscle during the concentric phase was analysed, it was noticed that the muscles on the left were more active than those on the right side, while in the eccentric phase the muscles had different behavior.     

Electromyographic analysis of the pectoralis major and deltoideus anterior muscles in horizontal "flyer" exercises with loads

The effective activity of the pectoralis major and deltoideus anterior muscles in horizontal "flyer" exercises with external loads of 25, 50, 75 and 100% of the maximum load was studied in 11 male volunteers. The electromyographic analysis was done by using MEDI-TRACE-200 surface electrodes connected to a biological signal acquisition mode coupled to a PC/AT computer. The electromyographic signals were processed and the values obtained were normalized through maximum voluntary isometric contraction. It was statistically observed that in all types and loads of this exercise, the muscles presented significant differences in the concentric and eccentric phases. In the concentric phase, when different loads were compared, the muscles were more active with 75 and 100% of the maximum load, while in the eccentric phase, higher activity was observed with 100% of the maximum load. By analyzing each load effect in the concentric phase, it was verified that the muscles on the left side were more active than those on the right side with 25, 75 and 100% of the maximum load.     

Muscle activation during maximal voluntary eccentric and concentric knee extension

Summary The aim of this investigation was to study the relationships among movement velocity, torque output and electromyographic (EMG) activity of the knee extensor muscles under eccentric and concentric loading. Fourteen male subjects performed maximal voluntary eccentric and concentric constant-velocity knee extensions at 45, 90, 180 and 360° · s^–1. Myoelectric signals were recorded, using surface electrodes, from the vastus medialis, vastus lateralis and rectus femoris muscles. For comparison, torque and full-wave rectified EMG signals were amplitude-averaged through the central half (30°–70°) of the range of motion. For each test velocity, eccentric torque was greater than concentric torque (range of mean differences: 20%–146%,P < 0.05). In contrast, EMG activity for all muscles was lower under eccentric loading than velocity-matched concentric loading (7%–31%,P < 0.05). Neither torque output nor EMG activity for the three muscles changed across eccentric test velocities (P > 0.05). While concentric torque increased with decreasing velocity, EMG activity for all muscles decreased with decreasing velocity (P < 0.05). These data suggest that under certain high-tension loading conditions (especially during eccentric muscle actions), the neural drive to the agonist muscles was reduced, despite maximal voluntary effort. This may protect the musculoskeletal system from an injury that could result if the muscle was to become fully activated under these conditions.     

Electromyographic analysis of the arm muscles in "front support" exercises

The electromyographic activity of the biceps brachii--BB (long head), triceps brachii--TB (long head) and deltoideus--DA (clavicular portion) muscles, during the going (G) and return (R) phases in "front support" exercise, as well the efficacy of this exercise for the development of these muscles strength were studied in 10 male volunteers. The values were normalized through maximum voluntary isometric contraction (MVIC = 100%) and statistically analyzed using the Friedman, DMS and Wilcoxon non-parametric test. A value of p < or = 0.05 indicated significance (Campos, 1983). All the muscles presented higher electromyographic activity in the return phase of the movement. The triceps brachii was the muscle which had higher activity in both phases of the movement. It was concluded that the "front support" exercise is efficient for strength development mainly in the triceps brachii muscle.     

Differences in leg muscle activity during running and cycling in humans

Delta (Δ) efficiency is defined as the ratio of an increment in the external mechanical power output to the increase in metabolic power required to produce it. The purpose of the present study was to investigate whether differences in leg muscle activity between running and cycling can explain the observed difference in Δ efficiency between the two activities. A group of 11 subjects performed incremental submaximal running and cycling tests on successive days. The Δ efficiencies during running and cycling were based on five exercise stages. Electromyograph (EMG) measurements were made of three leg muscles (gastrocnemius, vastus lateralis and biceps femoris). Kendall's correlation coefficients between the mean EMG activity and the load applied were calculated for each muscle, for both running and cycling. As expected, the mean Δ efficiency during running (42%) was significantly greater than that during cycling (25%). For cycling, all muscles showed a significant correlation between mean EMG activity and the load applied. For running, however, only the gastrocnemius muscle showed a significant, but low correlation (r=0.33). The correlation coefficients of the vastus lateralis and biceps femoris muscles were not significantly different from 0. The results were interpreted as follows. In contrast to cycling, which includes only concentric contractions, during running up inclines eccentric muscle actions play an important role. With steeper inclines, more concentric contractions must be produced to overcome the external force, whereas the amount of eccentric muscle actions decreases. This change in the relative contribution of concentric and eccentric muscle actions, in combination with the fact that eccentric muscle actions require much less metabolic energy than concentric contractions, can explain the difference between the running and cycling Δ efficiency. Electronic Publication     

EMG differences between concentric and eccentric maximum voluntary contractions are evident prior to movement onset

This investigation addressed the question of whether the muscle activation signal prior to movement onset, as measured by surface EMG, differs if the contraction to be performed is concentric (shortening) or eccentric (lengthening). Specifically, the purpose was to determine if differences in knee extensor muscle EMG prior to voluntary maximum concentric and eccentric contractions and initiated from the same knee joint angle are evident at a time before muscle length changes could be influential. A protocol was designed using isokinetic knee extensions. The EMG of the vastus lateralis, vastus medialis, rectus femoris, and hamstrings muscles and the associated knee extension moment were measured during the isometric phase preceding the onset of dynamometer motion. During this isometric phase the muscles initially contracted under identical conditions, irrespective of whether the contraction was to be concentric or eccentric. The EMG of the eccentric contractions was significantly smaller than that of the concentric contractions. However, the rate of change of knee extension moment generally did not differ between the two conditions. This was found for both the monoarticular and multiarticular knee extensor muscles. The results suggest that initial differences between the EMG of maximum voluntary concentric and eccentric knee extensor contractions are selected a priori and support the contention that the central nervous system distinguishes between maximum eccentric and concentric contractions. The emergence of differences in activation prior to muscle length changes suggests supraspinal influences.     

Muscular adaptations to computer-guided strength training with eccentric overload

AIMS: In order to investigate the muscular adaptations to a novel form of strength training, 18 male untrained subjects performed 4 weeks of low resistance-high repetition knee extension exercise. METHODS: Nine of them trained on a conventional weight resistance device (Leg curler, CON/ECC group), with loads equivalent to 30% of the concentric one-repetition maximum (1RM) for both the concentric and eccentric phase of movement. The other nine trained on a newly developed computer-driven device (CON/ECC-OVERLOAD group) with the concentric load equivalent to 30% of the concentric 1RM and the eccentric load equivalent to 30% of the eccentric 1RM. RESULTS: Training resulted in significantly (P < or = 0.05) increased peak torque and a tendency (P=0.092) to increased muscle cross-sectional area for the CON/ECC-OVERLOAD but not the CON/ECC group, while strength endurance capacity was significantly (P < or = 0.05) increased in the CON/ECC group only. RT-PCR revealed significantly increased myosin heavy chain (MHC) IIa and lactate dehydrogenase (LDH) A mRNAs, a tendency for increased MHC IIx mRNA (P = 0.056) and high correlations between the changes in MHC IIx and LDH A mRNAs (r=0.97, P=0.001) in the CON/ECC-OVERLOAD group. CONCLUSIONS: These results indicate a shift towards a more type II dominated gene expression pattern in the vasti laterales muscles of the CON/ECC-OVERLOAD group in response to training. We suggest that the increased eccentric load in the CON/ECC-OVERLOAD training leads to distinct adaptations towards a stronger, faster muscle.     

Modulation of EMG power spectrum frequency during motor imagery

To provide evidence that motor imagery (MI) is accompanied by improvement of intramuscular conduction velocity (CV), we investigated surface electromyographic (EMG) activity of 3 muscles during the elbow flexion/extension. Thirty right-handed participants were asked to lift or to imagine lifting a weighted dumbbell under 3 types of muscular contractions, i.e. concentric, isometric and eccentric, taken as independent variables. The EMG activity of the agonist (long and short heads of biceps brachii) and the antagonist (long portion of triceps brachii) muscles was recorded and processed to determine the median frequency (MF) of EMG power spectrum as dependant variable. The MF was significantly higher during the MI sessions than during the resting condition while the participants remained strictly motionless. Moreover, the MF during imagined concentric contraction was significantly higher than during the eccentric. Thus, the MF variation was correlated to the type of contraction the muscle produced. During MI, the EMG patterns corresponding to each type of muscle contraction remained comparable to those observed during actual movement. In conclusion, specific motor programming is hypothesized to be performed as a function of muscle contraction type during MI.     

Changes in Motor Unit Activity and Metabolism in Human Skeletal Muscle during and after Repeated Eccentric and Concentric Contractions

This study was designed to investigate electromyographic (EMG), muscle glycogen and blood lactate changes in quadriceps muscle group during repeated 40 maximal eccentric and concentric contractions, and to follow the recovery in EMG, muscle glycogen and serum creatine kinase values during a 4 day period following the work test. The subjects were normal males and the test order (eccentric or concentric) was randomly selected. The results indicated first, that the EMG parameters (IEMG, AMUP), muscle glycogen and blood lactate changed in a similar manner during the both fatigue loads. Despite the high tension work no selective depletion of glycogen could be observed in the slow or fast twitch muscle fibres in either type of work. The restoring of muscle glycogen occurred in a similar manner after the both fatigue loads, and no significant differences were present between eccentric and concentric works in the serum creatine kinase levels for a 2 days period. The eccentric work was associated with muscle soreness, which was strongest during the second day after the termination of the work test. The recovery of the EMG parameters were also delayed in eccentric fatigue. After concentric fatigue EMG-activity returned to normal values within 2 days.     

Muscular responses during motor imagery as a function of muscle contraction types.

This study was designed to gain more insight into the mechanisms underlying motor imagery (MI). While there is ample evidence that motor performance and MI share common central neural mechanisms, the question whether MI is accompanied by subliminal electromyographic (EMG) activity remained unsolved. Thirty right-handed volunteers were asked to lift or to imagine lifting a weighted dumbbell using different types of muscle contraction, i.e. heavy concentric, light concentric, isometric and eccentric contractions. EMG activity from 9 muscles of the dominant arm (agonist, antagonist, synergist and fixator muscles) was monitored. Autonomic nervous system responses were also recorded on the non-dominant hand, thus attesting mental activity at the peripheral level. A significant increased pattern of EMG activity was recorded in all muscles during MI, when compared to the rest condition, while the goniometric data did not reveal any movement. Although being subliminal, the magnitude of this activation was found to be correlated to the mental effort required to lift a weight mentally, as more EMG activity was recorded during imaginary lifting of heavy than light concentric contractions. When considering the different types of contraction, our results provided evidence of selective changes in EMG activity. Especially, the imagined eccentric condition elicited a significant weaker muscular activity than all other conditions. In addition, the changes in the EMG pattern mirrored those usually observed during physical movement. These findings support the hypotheses of a selective effect of MI at the level of muscular activity and of incomplete inhibition of the motor command during MI.     

Activation of quadriceps femoris including vastus intermedius during fatiguing dynamic knee extensions

Purpose

Fatigue-related muscle activity in the superficial quadriceps femoris (QF) muscles has been widely examined; however, there is no information on the activity of the deep vastus intermedius (VI) muscle during fatiguing dynamic knee extensions. The purpose of this study was to investigate neuromuscular activation patterns of the QF synergists, including the VI, during fatiguing dynamic knee extensions at two submaximal loads.

Methods

Nine healthy men performed dynamic knee extensions with loads of 50 and 70 % of one-repetition maximum (1RM) until failure. Muscle activation of the VI, vastus lateralis, vastus medialis (VM) and rectus femoris was recorded using surface electrodes. Root mean square (RMS) amplitude was calculated during the concentric (CON) and eccentric (ECC) phases of each repetition, and normalized to the RMS amplitude during the CON and ECC phases of the 1RM. Each CON and ECC phase was further divided into three subphases according to knee joint angle.

Results

The normalized RMS amplitude of the four individual QF muscles during the CON phase linearly increased with fatigue with contractions at both 50 and 70 % 1RM. The highest RMS amplitude was found in VI at flexed knee joint angles until fatigue. This activation pattern was more prominent at 70 % 1RM than 50 % 1RM. The RMS amplitude of VM at extended knee joint angles was selectively higher at 70 % 1RM than 50 % 1RM.

Conclusions

These results suggest that the contribution of the four individual QF muscles to fatiguing dynamic knee extensions differs according to knee joint angle and intensity of load.     

Greater movement-related cortical potential during human eccentric versus concentric muscle contractions

Despite abundant evidence that different nervous system control strategies may exist for human concentric and eccentric muscle contractions, no data are available to indicate that the brain signal differs for eccentric versus concentric muscle actions. The purpose of this study was to evaluate electroencephalography (EEG)-derived movement-related cortical potential (MRCP) and to determine whether the level of MRCP-measured cortical activation differs between the two types of muscle activities. Eight healthy subjects performed 50 voluntary eccentric and 50 voluntary concentric elbow flexor contractions against a load equal to 10% body weight. Surface EEG signals from four scalp locations overlying sensorimotor-related cortical areas in the frontal and parietal lobes were measured along with kinetic and kinematic information from the muscle and joint. MRCP was derived from the EEG signals of the eccentric and concentric muscle contractions. Although the elbow flexor muscle activation (EMG) was lower during eccentric than concentric actions, the amplitude of two major MRCP components-one related to movement planning and execution and the other associated with feedback signals from the peripheral systems-was significantly greater for eccentric than for concentric actions. The MRCP onset time for the eccentric task occurred earlier than that for the concentric task. The greater cortical signal for eccentric muscle actions suggests that the brain probably plans and programs eccentric movements differently from concentric muscle tasks.     

Co-activation of vastus lateralis and biceps femoris muscles in pubertal children and adults

Determining the mechanisms of co-activation around the knee joint with respect to age and sex is important in terms of our greater understanding of strength development. The purpose of this study was to examine the effects of age, sex and muscle action on moment of force and electromyographic (EMG) activity of the agonist and antagonist muscle groups during isokinetic eccentric and concentric knee extension and flexion. The study comprised nine pubertal boys [mean age 12.6 (SD 0.5) years], nine girls [12.7 (SD 0.5) years] nine adult men [23.1 (SD 2.1) years] and nine adult women [23.7 (SD 3.1) years] who performed maximal isometric eccentric and concentric efforts of knee extensors and flexors on a dynamometer at 30°?·?s^?1. The moment of force and surface EMG activity of vastus lateralis and biceps femoris muscles were recorded. The moment of force:agonist averaged EMG (aEMG) ratios were calculated. The antagonist aEMG values were expressed as a percentage of the aEMG activity of the same muscle, at the same angle, angular velocity and muscle action when the muscle was acting as agonist. Three-way analysis of variance (ANOVA) designs indicated no significant effects of age or sex on moment:aEMG ratios. Eccentric ratios were significantly higher than the corresponding concentric ones (P?P?相似文献   

Muscular adaptations to computer‐guided strength training with eccentric overload

Aims: In order to investigate the muscular adaptations to a novel form of strength training, 18 male untrained subjects performed 4 weeks of low resistance–high repetition knee extension exercise. Methods: Nine of them trained on a conventional weight resistance device (Leg curler, CON/ECC group), with loads equivalent to 30% of the concentric one‐repetition maximum (1RM) for both the concentric and eccentric phase of movement. The other nine trained on a newly developed computer‐driven device (CON/ECC‐OVERLOAD group) with the concentric load equivalent to 30% of the concentric 1RM and the eccentric load equivalent to 30% of the eccentric 1RM. Results: Training resulted in significantly (P ≤ 0.05) increased peak torque and a tendency (P = 0.092) to increased muscle cross‐sectional area for the CON/ECC‐OVERLOAD but not the CON/ECC group, while strength endurance capacity was significantly (P ≤ 0.05) increased in the CON/ECC group only. RT‐PCR revealed significantly increased myosin heavy chain (MHC) IIa and lactate dehydrogenase (LDH) A mRNAs, a tendency for increased MHC IIx mRNA (P = 0.056) and high correlations between the changes in MHC IIx and LDH A mRNAs (r = 0.97, P = 0.001) in the CON/ECC‐OVERLOAD group. Conclusions: These results indicate a shift towards a more type II dominated gene expression pattern in the vasti laterales muscles of the CON/ECC‐OVERLOAD group in response to training. We suggest that the increased eccentric load in the CON/ECC‐OVERLOAD training leads to distinct adaptations towards a stronger, faster muscle.     

Electromyographic fatigue threshold of the biceps brachii: the effect of endurance time

Muscle fatigue can be a limiting factor to determine index as the electromyographic fatigue threshold (EMGFT) due the alterations in motivation and disconfots. This way, the purpose of this study was to identify the right biceps brachii and left biceps brachii obtained from repetitive elbow flexions at each 100% of total time. Nine healthy subjects performed the exercise named biceps curl until exhaustion with 25%, 35%, and 45%0 of one repetition maximum, in three different days. EMG amplitude (root mean square--RMS) was obtained for concentric contractions during these load levels and correlated with time to determine the slope values for each load and them determine the EMGFT. The EMGFT was obtained within of each 10% of total time and they were compared by analysis of variance. The results showed a progressive increase in RMS with time, for both muscles in all loads, characterizing the muscle fatigue process, and for the EMGFT values ware not found predominantly significant differences between the execution time, as well as between muscles (right biceps x left biceps). This protocol allowed to identify the EMGFT to both muscles during the biceps curl, which was similar at different percentage of total time, indicating the possibility to reduce the length of the contraction test without the need to maintain the contraction until exhaustion. Further studies are needed to evaluate the applicability of this method to determining the effects on performance.     

Viscosity of the elbow flexor muscles during maximal eccentric and concentric actions

The aim of the present study was to estimate the damping coefficient (B factor) of the elbow flexor muscles during both eccentric and concentric muscle actions. We used a muscle model consisting of a viscous damper associated in parallel with a contractile component, both in series with an elastic component. The viscous damper allowed the concentric loss and the eccentric gain of force to be modelled. Eight volunteer subjects performed maximal eccentric and concentric elbow movements on an isokinetic dynamometer at angular velocities of 0.52, 1.04 and 2.09 rad·s^–1. Torques at an elbow joint angle of 90° were recorded. Electromyogram (EMG) signals from the belly of the right elbow flexor and from the long head of the triceps brachia muscles were recorded using two pairs of bipolar surface electrodes. The root mean square (rms) of the EMG was determined. Eccentric and concentric rms were not significantly different (P>0.05). The B factor was higher in the concentric than in the eccentric conditions (P<0.05), and, whatever the muscle action type it decreased as the velocity increased. These results indicated that the concentric loss and the eccentric gain of force were attributable to the behaviour of the contractile machinery. Furthermore, whatever the exact cause of loss and gain of tension, our study showed that the total effect can be modelled by the viscous damper of a three-component muscle model.     

Mechanical efficiency of locomotion in females during different kinds of muscle action

Summary The mechanical efficiencies (ME) of pure positive and pure negative work as well as of stretch-shortening cycle (SSC) exercise were investigated with a special sledge apparatus. The subjects were 20 young females who performed six different types of submaximal exercise: two of pure concentric exercise (positive work), two of pure eccentric exercise (negative work) and two SSC exercises. The work intensities were determined individually, from the recordings of distance obtained during a single maximal concentric exercise. Each exercise involved 60 muscle actions lasting a total of 3 min per testing condition. The MEs of pure positive work with intensities of 30% and 60% maximum (C₃₀ and C₆₀ respectively) were 15.5%, SD 2.6% and 14.3%, SD 1.9%, respectively. In pure negative work, when the dropping heights were 20 cm (E₂₀) and 80 cm (E₈₀), MEs were 28.4%, SD 6.9% and 47.9%, SD 10.1%, respectively. In SSC-exercise, the MEs during the positive phase of the take-off were 31.3%, SD 6.3% (E₂₀/C₉₀) and 35.0%, SD 7.0% (E₈₀/C₆₉). The total MEs in SSC-exercise were 29.1%, SD 4.0% (E₂₀/C₉₀) and 40.1%, SD 5.2% (E₈₀/C₆₀ × 100). In pure negative work, the increased stretching velocity increased the value of ME. In the concentric phase of SSC-exercise, the integrated electromyographic activity (iEMG) of vastus lateralis (VL) and vastus medialis (VM) muscles were lower (P<0.05) than in pure concentric work, when the mechanical work was the same (C₆₀ vs E₈₀/C₆₀). During pure eccentric work, iEMGs were lower in comparison to the eccentric phase of SSC-exercise. The EMG activity of VL, VM and soleus muscles was potentiated in SSC-exercise during the eccentric phase of the take-off, when the dropping height was 80 cm. The results of the present study demonstrate the role of stretch reflexes as an increasing factor of ME in the positive work of SSC-exercise, when prestretch intensity is high enough. When muscle stiffness increases via reflex pathways, it may also increase the elasticity of the muscles and decrease their metabolic demands.     

Concentric and eccentric muscle strength before,during and after fatigue in 13 year-old boys

Summary The purpose of this study was to investigate the force-producing characteristics of boys aged 13 years in relation to fatigue of elbow flexor muscles. Maximal voluntary force in elbow flexion was measured before and after a muscle endurance test (MET) by using an isokinetic dynamometer isometrically, concentrically and eccentrically at three velocities, i.e. 0.21, 0.52, and 1.05 rad · s^–1. The MET consisted of maximal concentric and eccentric muscle actions performed alternately at 0.52 rad · s^–1 for 50 consecutive trials. Muscle cross-sectional area (CSA) of elbow flexor muscles (biceps brachii and brachialis) was measured by a B-mode ultrasound apparatus. Although eccentric force showed significantly higher values than concentric force during MET, there was no significant difference in the rate of decline in force between the two actions. There was no significant difference in the rate of decline in force after MET for each velocity and muscle action. Isometric, concentric and eccentric force before MET was significantly related to muscle CSA whereas, after MET, concentric force significantly correlated with muscle CSA but there was no significant correlation between muscle CSA and isometric or eccentric force. From our study, it is therefore suggested that in development to maturity, isometric, concentric and eccentric force decrease at the same rate with advancing muscle fatigue; however, there might be differences among muscle actions in facors affecting force development.     

Electromyographic analysis of the arm muscles in "back support" exercises

This study aims at quantifying through electromyography the actions of the biceps brachii-BB (long head), triceps brachii-TB (long head) and deltoideus-DA (clavicular portion) muscles, during the going (G) and return (R) phases in "back support" exercises. Surface electrodes were placed at the muscles, according to DELAGI (1981). It was used a specific software and a A/D plate to take the signals. After being collected, the records were processed resulting in efficient values (RMS), were normalized by maximum isometric contraction (MVIC = 100%) and statistically analysed using the Friedman, DSM and Wilcox non-parametric tests. All the muscles presented electromyographic activity of the movements. The triceps brachii was the muscle with higher activity in both phases of the movement. It was concluded that the exercise is indicated for the arm muscle strength development.     

Muscle architecture and EMG activity changes during isotonic and isokinetic eccentric exercises

The present study aimed to compare muscle architecture and electromyographic activity during isotonic (IT) and isokinetic (IK) knee extensors eccentric contractions. Seventeen subjects were assigned in test and reproducibility groups. During test session, subjects performed two IT and two IK sets of eccentric contractions of knee extensor muscles. Torque, angular velocity, VL architecture and EMG activity of agonist (vastus lateralis, VL; vastus medialis; rectus femoris) and antagonist (semitendinosus; biceps femoris, BF) muscles were simultaneously recorded and averaged on a 5° window. Torque–angle and angular velocity–angle relationships exhibited differences in mechanical load between the IT and IK modes. Changes in muscle architecture were similar in both modes, since VL fascicles length increased and fascicle angle decreased, resulting in a decrease in muscle thickness during eccentric contraction. Agonist activity and BF co-activity levels were higher in IT mode than in IK mode at short muscle lengths, whereas agonist activity was higher in IK mode than in IT mode at long muscle lengths. Differences in mechanical load between both modes induced specific neuromuscular responses in terms of agonist activity and antagonist co-activity. These results suggest that specific neural adaptations may occur after IT or IK eccentric training. This hypothesis needs to be tested in order to gain new insights concerning the most effective eccentric protocols based on whether the objective is sportive or clinical.