Search

This study aimed to compare neuromuscular alterations and perceptions of effort and muscle pain induced by concentric and eccentric cycling performed at the same power output or effort perception. Fifteen participants completed three 30-min sessions: one in concentric at 60% peak power output (CON) and two in eccentric, at the same power output (ECCPOWER ) or same perceived effort (ECCEFFORT ). Muscle pain, perception of effort, oxygen uptake as well as rectus femoris and vastus lateralis electromyographic activities were collected when pedaling. The knee extensors maximal voluntary contraction (MVC) torque, the torque evoked by double stimulations at 100 Hz and 10 Hz (Dt100; Dt10), and the voluntary activation level (VAL) were evaluated before and after exercise. Power output was higher in ECCEFFORT than CON (89.1 ± 23.3% peak power). Muscle pain and effort perception were greater in CON than ECCPOWER (p 0.43). MVC torque, Dt100, and VAL dropped in all conditions (p

Corticospinal excitability, and particularly the balance between cortical inhibitory and excitatory processes (assessed in a muscle using single and paired-pulse transcranial magnetic stimulation), are affected by neurodegenerative pathologies or following a stroke. This review describes how locomotor exercises may counterbalance these neuroplastic alterations, either when performed under its conventional form (e.g., walking or cycling) or when comprising eccentric (i.e., active lengthening) muscle contractions. Non-fatiguing conventional locomotor exercise decreases intracortical inhibition and/or increases intracortical facilitation. These modifications notably seem to be a consequence of neurotrophic factors (e.g., brain-derived neurotrophic factor) resulting from the hemodynamic solicitation. Furthermore, it can be inferred from non-invasive brain and peripheral stimulation studies that repeated activation of neural networks can endogenously shape neuroplasticity. Such mechanisms could also occur following eccentric exercises (lengthening of the muscle), during which motor-related cortical potential (electroencephalography) is of greater magnitude and lasts longer than during concentric exercises (i.e., muscle shortening). As single-joint eccentric exercise decreased short- and long-interval intracortical inhibition and increased intracortical facilitation, locomotor eccentric exercise (e.g., downhill walking or eccentric cycling) may be even more potent by adding hemodynamic-related neuroplastic processes to endogenous processes. Besides, eccentric exercise is especially useful to develop relatively high force levels at low cardiorespiratory and perceived intensities, which can be a training goal alongside the induction of neuroplastic changes. Even though indirect evidence let us think that locomotor eccentric exercise could shape neuroplasticity in ways relevant to neurorehabilitation, its efficacy remains speculative. We provide future research directions on the neuroplastic effects and underlying mechanisms of locomotor exercise.

Your muscles can contract in different ways: when you walk upstairs, the muscles at the fronts of your thighs shorten (concentric contraction), whereas when you walk downstairs, they lengthen (eccentric contraction). Concentric contractions require more oxygen and thus make you burn more calories. Eccentric contractions are easier but break parts of the muscle and make you feel sore for several days. If you repeat eccentric exercises, however, your muscles will probably get bigger and stronger than they would by repeating concentric contractions. Most physical activities (like running and jumping) include both concentric and eccentric phases. Scientists have designed tools to study each type of muscle contraction, such as eccentric cycling, which uses a bike on which you must resist the pedals as they are driven backward by an engine.

Corticospinal excitability and particularly the balance between cortical inhibitory and excitatory processes (assessed in a muscle using transcranial magnetic stimulation), are affected by neurodegenerative pathologies or following a stroke. Non-fatiguing conventional locomotor exercise, such as cycling or walking, decreases intracortical inhibition and/or increases intracortical facilitation. These modifications notably seem to be a consequence of neurotrophic factors (e.g., brain-derived neurotrophic factors) resulting from hemodynamic solicitation. Furthermore, it can be inferred from non-invasive brain and peripheral stimulation studies that repeated activation of neural networks can endogenously shape neuroplasticity. Such mechanisms could also occur following eccentric exercises (i.e., active lengthening of the muscle), during which motor-related cortical potential is of greater magnitude and lasts longer (assessed by electroencephalography) than during concentric exercises (i.e., muscle shortening). As single-joint eccentric exercise decreased short- and long-interval intracortical inhibition and increased intracortical facilitation (assessed by paired-pulse transcranial magnetic stimulation immediately after), locomotor eccentric exercise may be even more potent by adding hemodynamic-related neuroplastic processes to endogenous processes. Besides, eccentric exercise is especially useful to develop relatively high force levels at low cardiorespiratory and perceived intensity, which can be a training goal in addition to inducing neuroplastic changes. Further studies are required to understand how neuroplasticity is 1) acutely influenced by locomotor exercise characteristics (e.g., intensity, duration), 2) modulated by an exercise-based rehabilitation program, 3) related to functional cognitive and motor outcomes relevant to pathological population.

International audience; Purpose To examine corticospinal excitability and neuromuscular function following the completion of eccentric (ECC) or concentric (CON) maximal exercises of same mechanical work. Methods Ten males (29.9 +/- 11.8 years) performed maximal isokinetic knee extensor contractions in four experimental sessions. The two first sessions (one in ECC and one in CON) ended with a dynamic peak torque loss of 20%. The work completed in each contraction type was then achieved in the other contraction type. Neuromuscular function- maximal voluntary isometric contraction (MVIC), voluntary activation level (VAL), potentiated doublet (Dt), M-wave- and corticospinal excitability- motor evoked potential (MEP) amplitude and silent period (SP)-were assessed in the vastus lateralis (VL) and rectus femoris (RF) muscles at 20% MVIC before and immediately after exercise. Results To lose 20% of dynamic peak torque subjects performed 1.8 times more work in ECC than CON (P = 0.03), inducing a non-different decline in MVIC (P = 0.15). VAL dropped after the ECC sessions only (- 8.5 +/- 6.7%; all P < 0.027). Only, the CON session featuring the greatest work affected Dt amplitude (- 9.4 +/- 23.8%; P = 0.047). In both muscles, MEP amplitude decreased (all P < 0.001) and MEP SP stayed constant (all P > 0.45), irrespective of contraction type (all P > 0.15). Conclusion Same-work maximal ECC and CON exercises induced similar fatigue level but from different origins (preferentially central for ECC vs peripheral for CON). Yet, net corticospinal excitability did not depend on contraction type.

As discussed in the current Viewpoint (2), there have been a number of methodologically different applications of the verification phase for maximal oxygen uptake (Vo2max) over the past decade, incorporating seemingly arbitrary determination criteria. This is not to say that through observation and experiment, a more exact validation cannot be found. But rather, the immediate focus should be on developing updated protocols for accurately identifying Vo2max for various populations...

To the editor: We read with interest the recent Viewpoint on the different eccentric exercise modalities (4), and we commend the authors for having raised this interesting topic. Since the eccentric-exercise family is variegated, characterizing each modality helps in identifying their specific intrinsic stimuli. However, a between-modality comparison is not an easy matter. Exercise volume is a key factor in resistance training. A recent meta-analysis showed comparable exercise volumes led to similar strength gains (5). When performing an isoweight eccentric exercise, the volume can be manipulated a priori, given the total number of repetitions and for each repetition the range of motion, time under tension, and intensity (i.e., the external load) (2). When performing an isokinetic eccentric exercise, the intensity depends on the subject’s ability to gradually or maximally perform each repetition. To possibly match the eccentric isoweight vs isokinetic exercise intensity, we previously calculated the maximal eccentric:concentric isokinetic ratio and then transferred such a ratio as a percentage of the maximal concentric isoweight load (i.e., %1-RM) (2). It resulted in comparable isoweight versus isokinetic training intensity and volume, which led to overall similar muscle strength and architecture changes (2, 3). To further entangle this picture, the eccentric phase of isoinertial exercise is preceded by a maximal explosive-concentric phase (1). Thus, isoinertial cannot be considered as a purely eccentric exercise because of the effects of the eccentric or concentric phase, or the combination of both. Therefore, encouraging new studies to compare isoweight versus isokinetic versus isoinertial eccentric training, we recommend a thorough exercise volume calculation for appropriate matching.