Eccentric exercise: many questions unanswered

Skeletal Muscle Heat Shock Protein Content and the Repeated Bout Effect

The "Repeated Bout Effect" (RBE) occurs when a skeletal muscle is preconditioned with a few lengthening contractions (LC) prior to exposing the muscle to a greater number of LC. The preconditioning (PC) results in significantly less damage and preservation of force. Since it takes only a few LC to increase muscle heat shock protein (HSP) content, it was of interest to examine the relationship between HSPs and the RBE. To do this, one tibialis anterior (TA) muscle from Sprague-Dawley rats (n = 5/group) was preconditioned with either 0, 5, or 15 lengthening contractions (LC) and exposed to a treatment of 60 LC 48 h later. Preconditioning TA muscles with 15 LC, but not 5 LC, significantly elevated muscle αB-crystallin (p < 0.05), HSP25 (p < 0.05), and HSP72 content (p < 0.001). These preconditioned TA muscles also showed a significantly (p < 0.05) reduced loss of active torque throughout the subsequent 60 LC. While there was a trend for all preconditioned muscles to maintain higher peak torque levels throughout the 60 LC, no significant differences were detected between the groups. Morphologically, preconditioned muscles appeared to show less discernible muscle fiber damage. In conclusion, an elevated skeletal muscle HSP content from preconditioning may contribute to the RBE.

Should We Void Lactate in the Pathophysiology of Delayed Onset Muscle Soreness? Not So Fast! Let's See a Neurocentric View!

The pathophysiology of delayed onset muscle soreness is not entirely known. It seems to be a simple, exercise-induced delayed pain condition, but has remained a mystery for over 120 years. The buildup of lactic acid used to be blamed for muscle fatigue and delayed onset muscle soreness; however, studies in the 1980s largely refuted the role of lactate in delayed onset muscle soreness. Regardless, this belief is widely held even today, not only in the general public, but within the medical and scientific community as well. Current opinion is highlighting lactate's role in delayed onset muscle soreness, if neural dimension and neuro-energetics are not overlooked. By doing so, lactate seems to have an essential role in the initiation of the primary damage phase of delayed onset muscle soreness within the intrafusal space. Unaccustomed or strenuous eccentric contractions are suggested to facilitate lactate nourishment of proprioceptive sensory neurons in the muscle spindle under hyperexcitation. However, excessive acidosis and lactate could eventually contribute to impaired proprioception and increased nociception under pathological condition. Furthermore, lactate could also contribute to the secondary damage phase of delayed onset muscle soreness in the extrafusal space, primarily by potentiating the role of bradykinin. After all, neural interpretation may help us to dispel a 40-year-old controversy about lactate's role in the pathophysiology of delayed onset muscle soreness.

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 (χ214 = 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.

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.

Motor Cortical Excitability Changes in Preparation to Concentric and Eccentric Movements

Specific neural mechanisms operate at corticospinal levels during eccentric and concentric contractions. Here, we investigated the difference in corticospinal excitability (CSE) when preparing these two types of contraction. In this study we enrolled 16 healthy participants. They were asked to perform an instructed-delay reaction time (RT) task involving a concentric or an eccentric contraction of the right first dorsal interosseus muscle, as a response to a proprioceptive cue (Go signal) presented 1 s after a warning signal. We tested CSE at different time points ranging from 300 ms before up to 40 ms after a Go signal. CSE increased 300-150 ms before the Go signal for both contractions. Interestingly, significant changes in CSE in the time interval around the Go signal (from -150 ms to +40 ms) were only revealed in eccentric contraction. We observed a significant decrease in excitability immediately before the Go cue (Pre_50) and a significant increase 40 ms after it (Post_40) with respect to the MEPs recorded at Pre_150. Finally, CSE in eccentric contraction was lower before the Go cue (Pre_50) and greater after it (Post_40) compared to the concentric contraction. A similar result was also found in NoMov paradigm, used to disentangle the effects induced by movement preparation from those induced by the movement preparation linked to the proprioceptive cue. We could conclude that different neural mechanisms observed during concentric and eccentric contractions are mirrored with a different time-specific modulation of CSE in the preparatory phase to the movement.

Does Compression Sensory Axonopathy in the Proximal Tibia Contribute to Noncontact Anterior Cruciate Ligament Injury in a Causative Way?-A New Theory for the Injury Mechanism

Anterior cruciate ligament injury occurs when the ligament fibers are stretched, partially torn, or completely torn. The authors propose a new injury mechanism for non-contact anterior cruciate ligament injury of the knee. Accordingly, non-contact anterior cruciate ligament injury could not happen without the acute compression microinjury of the entrapped peripheral proprioceptive sensory axons of the proximal tibia. This would occur under an acute stress response when concomitant microcracks-fractures in the proximal tibia evolve due to the same excessive and repetitive compression forces. The primary damage may occur during eccentric contractions of the acceleration and deceleration moments of strenuous or unaccustomed fatiguing exercise bouts. This primary damage is suggested to be an acute compression/crush axonopathy of the proprioceptive sensory neurons in the proximal tibia. As a result, impaired proprioception could lead to injury of the anterior cruciate ligament as a secondary damage, which is suggested to occur during the deceleration phase. Elevated prostaglandin E2, nitric oxide and glutamate may have a critical neuro-modulatory role in the damage signaling in this dichotomous neuronal injury hypothesis that could lead to mechano-energetic failure, lesion and a cascade of inflammatory events. The presynaptic modulation of the primary sensory axons by the fatigued and microdamaged proprioceptive sensory fibers in the proximal tibia induces the activation of N-methyl-D-aspartate receptors in the dorsal horn of the spinal cord, through a process that could have long term relevance due to its contribution to synaptic plasticity. Luteinizing hormone, through interleukin-1β, stimulates the nerve growth factor-tropomyosin receptor kinase A axis in the ovarian cells and promotes tropomyosin receptor kinase A and nerve growth factor gene expression and prostaglandin E2 release. This luteinizing hormone induced mechanism could further elevate prostaglandin E2 in excess of the levels generated by osteocytes, due to mechanical stress during strenuous athletic moments in the pre-ovulatory phase. This may explain why non-contact anterior cruciate ligament injury is at least three-times more prevalent among female athletes.

Delayed Onset Muscle Soreness (DOMS): The Repeated Bout Effect and Chemotherapy-Induced Axonopathy May Help Explain the Dying-Back Mechanism in Amyotrophic Lateral Sclerosis and Other Neurodegenerative Diseases

Delayed onset muscle soreness (DOMS) is hypothesized to be caused by glutamate excitotoxicity-induced acute compression axonopathy of the sensory afferents in the muscle spindle. Degeneration of the same sensory afferents is implicated in the disease onset and progression of amyotrophic lateral sclerosis (ALS). A series of “silent” acute compression proprioceptive axonopathies with underlying genetic/environmental factors, damaging eccentric contractions and the non-resolving neuroinflammatory process of aging could lead to ALS disease progression. Since the sensory terminals in the muscle spindle could not regenerate from the micro-damage in ALS, unlike in DOMS, the induced protective microcircuits and their long-term functional plasticity (the equivalent of the repeated bout effect in DOMS) will be dysfunctional. The acute stress invoking osteocalcin, bradykinin, COX1, COX2, GDNF, PGE2, NGF, glutamate and N-methyl-D-aspartate (NMDA) receptors are suggested to be the critical signalers of this theory. The repeated bout effect of DOMS and the dysfunctional microcircuits in ALS are suggested to involve several dimensions of memory and learning, like pain memory, inflammation, working and episodic memory. The spatial encoding of these memory dimensions is compromised in ALS due to blunt position sense from the degenerating proprioceptive axon terminals of the affected muscle spindles. Dysfunctional microcircuits progressively and irreversibly interfere with postural control, with motor command and locomotor circuits, deplete the neuroenergetic system, and ultimately interfere with life-sustaining central pattern generators in ALS. The activated NMDA receptor is suggested to serve the “gate control” function in DOMS and ALS in line with the gate control theory of pain. Circumvention of muscle spindle-loading could be a choice of exercise therapy in muscle spindle-affected neurodegenerative diseases.

Moving forward with backward pedaling: a review on eccentric cycling

PURPOSE

There is a profound gap in the understanding of the eccentric cycling intensity continuum, which prevents accurate exercise prescription based on desired physiological responses. This may underestimate the applicability of eccentric cycling for different training purposes. Thus, we aimed to summarize recent research findings and screen for possible new approaches in the prescription and investigation of eccentric cycling.

METHOD

A search for the most relevant and state-of-the-art literature on eccentric cycling was conducted on the PubMed database. Literature from reference lists was also included when relevant.

RESULTS

Transversal studies present comparisons between physiological responses to eccentric and concentric cycling, performed at the same absolute power output or metabolic load. Longitudinal studies evaluate responses to eccentric cycling training by comparing them with concentric cycling and resistance training outcomes. Only one study investigated maximal eccentric cycling capacity and there are no investigations on physiological thresholds and/or exercise intensity domains during eccentric cycling. No study investigated different protocols of eccentric cycling training and the chronic effects of different load configurations.

CONCLUSION

Describing physiological responses to eccentric cycling based on its maximal exercise capacity may be a better way to understand it. The available evidence indicates that clinical populations may benefit from improvements in aerobic power/capacity, exercise tolerance, strength and muscle mass, while healthy and trained individuals may require different eccentric cycling training approaches to benefit from similar improvements. There is limited evidence regarding the mechanisms of acute physiological and chronic adaptive responses to eccentric cycling.

31 P magnetic resonance spectroscopy in skeletal muscle: Experts' consensus recommendations

Skeletal muscle phosphorus-31 31 P MRS is the oldest MRS methodology to be applied to in vivo metabolic research. The technical requirements of 31 P MRS in skeletal muscle depend on the research question, and to assess those questions requires understanding both the relevant muscle physiology, and how 31 P MRS methods can probe it. Here we consider basic signal-acquisition parameters related to radio frequency excitation, TR, TE, spectral resolution, shim and localisation. We make specific recommendations for studies of resting and exercising muscle, including magnetisation transfer, and for data processing. We summarise the metabolic information that can be quantitatively assessed with 31 P MRS, either measured directly or derived by calculations that depend on particular metabolic models, and we give advice on potential problems of interpretation. We give expected values and tolerable ranges for some measured quantities, and minimum requirements for reporting acquisition parameters and experimental results in publications. Reliable examination depends on a reproducible setup, standardised preconditioning of the subject, and careful control of potential difficulties, and we summarise some important considerations and potential confounders. Our recommendations include the quantification and standardisation of contraction intensity, and how best to account for heterogeneous muscle recruitment. We highlight some pitfalls in the assessment of mitochondrial function by analysis of phosphocreatine (PCr) recovery kinetics. Finally, we outline how complementary techniques (near-infrared spectroscopy, arterial spin labelling, BOLD and various other MRI and 1 H MRS measurements) can help in the physiological/metabolic interpretation of 31 P MRS studies by providing information about blood flow and oxygen delivery/utilisation. Our recommendations will assist in achieving the fullest possible reliable picture of muscle physiology and pathophysiology.

Eccentric Muscle Contractions: Risks and Benefits

Eccentric contractions, characterized by the lengthening of the muscle-tendon complex, present several unique features compared with other types of contractions, which may lead to unique adaptations. Due to its specific physiological and mechanical properties, there is an increasing interest in employing eccentric muscle work for rehabilitation and clinical purposes. However, unaccustomed eccentric exercise is known to cause muscle damage and delayed pain, commonly defined as “Delayed-Onset Muscular Soreness” (DOMS). To date, the most useful preventive strategy to avoid these adverse effects consists of repeating sessions involving submaximal eccentric contractions whose intensity is progressively increased over the training. Despite an increased number of investigations focusing on the eccentric contraction, a significant gap still remains in our understanding of the cellular and molecular mechanisms underlying the initial damage response and subsequent adaptations to eccentric exercise. Yet, unraveling the molecular basis of exercise-related muscle damage and soreness might help uncover the mechanistic basis of pathological conditions as myalgia or neuromuscular diseases. In addition, a better insight into the mechanisms governing eccentric training adaptations should provide invaluable information for designing therapeutic interventions and identifying potential therapeutic targets.

Supramaximal Eccentrics Versus Traditional Loading in Improving Lower-Body 1RM: A Meta-Analysis

Guidelines for improving maximal concentric strength through resistance training (RT) have traditionally included large muscle-group exercises, full ranges of motion, and a load approximating 85% of the 1-repetition maximum (1RM). Supramaximal eccentric training (SME; controlled lowering of loads above the concentric 1RM) has also been shown to be effective at increasing concentric 1RM in the lower body, but concerns regarding injury risk, postexercise soreness, and null benefit over traditional methods (TRAD) may limit the practical utility of this approach.

PURPOSE

The purpose of this study was to determine whether SME elicits greater lower-body strength improvements than TRAD.

METHOD

Key inclusion criteria were regular exercise modalities typical of nonspecialized exercise facilities (e.g., leg press; key exclusion: isokinetic dynamometer) and at least 6 weeks of RT exposure, leading to 5 studies included in the current meta-analysis. Unbiased effect-size measures that quantify the mean difference in lower-body 1RM between SME and TRAD were extracted.

RESULTS

Supramaximal eccentric training did not appear to be more effective than TRAD at increasing lower-body 1RM ([Formula: see text] = .33, SE = .26, z = 1.26, 95% CI [-0.20, 0.79], p = .20, I² = 56.78%) under a random-effects model where between-study variance was estimated using maximum likelihood estimation ([Formula: see text] 2 = .25).

CONCLUSION

The selection of SME over TRAD in RT programs designed to increase lower-body 1RM does not appear warranted in all populations. Further research should clarify the merit of periodic SME in TRAD-dominant RT programs as well as whether a differential effect exists in trained individuals.

Basic science and clinical use of eccentric contractions: History and uncertainties

The peculiar attributes of muscles that are stretched when active have been noted for nearly a century. Understandably, the focus of muscle physiology has been primarily on shortening and isometric contractions, as eloquently revealed by A.V. Hill and subsequently by his students. When the sliding filament theory was introduced by A.F. Huxley and H.E. Huxley, it was a relatively simple task to link Hill's mechanical observations to the actions of the cross bridges during these shortening and isometric contractions. In contrast, lengthening or eccentric contractions have remained somewhat enigmatic. Dismissed as necessarily causing muscle damage, eccentric contractions have been much more difficult to fit into the cross-bridge theory. The relatively recent discovery of the giant elastic sarcomeric filament titin has thrust a previously missing element into any discussion of muscle function, in particular during active stretch. Indeed, the unexpected contribution of giant elastic proteins to muscle contractile function is highlighted by recent discoveries that twitchin-actin interactions are responsible for the "catch" property of invertebrate muscle. In this review, we examine several current theories that have been proposed to account for the properties of muscle during eccentric contraction. We ask how well each of these explains existing data and how an elastic filament can be incorporated into the sliding filament model. Finally, we review the increasing body of evidence for the benefits of including eccentric contractions into a program of muscle rehabilitation and strengthening.

Eccentric cycling emphasising a low cardiopulmonary demand increases leg strength equivalent to workload matched concentric cycling in middle age sedentary males

OBJECTIVES

This study determined if eccentric endurance cycling, eliciting a low cardiovascular demand, could stimulate muscle strength adaptations in sedentary middle-aged males.

DESIGN

Twenty-four middle-aged sedentary males were allocated to concentric (CON) or matched workload eccentric (ECC) cycling (60% peak concentric workload) according to their maximal voluntary isometric quadriceps strength.

METHODS

Seventeen participants [42.7±8.3 years, BMI 28.6±5.2, peak oxygen consumption [30.5±5.8mLkg^-1min^-1] completed 8 weeks (2 sessions per week) of CON (n=8) or ECC (n=9) cycle training. Incline leg press (6RM), maximal voluntary isometric contraction (MVIC) torque of the quadriceps and peak oxygen consumption were measured at baseline and 8 weeks.

RESULTS

Eccentric cycle training resulted in low cardiovascular demand (CON 154±2; ECC 95±3bmin^-1P<0.05) and ratings of perceived exertion (CON 14.9±0.3; ECC 9.5±0.3/20 P<0.05). Peak oxygen consumption improved within the CON group (Baseline 27.4±2.1; 8 weeks: 30.0±1.7mLkg^-1min^-1P<0.05) and not within the ECC group (Baseline 33.2±1.5; 8 weeks 33.3±1.6mLkg^-1min^-1) following training. 6RM (CON 176±20; ECC 192±11kg) and MVIC (CON 199±25; ECC 199±25Nm) strength were equivalent at baseline (P>0.05). Both groups significantly increased 6RM (CON 13.0±3.0; ECC 10.7±3.2%) and MVIC (CON 12.9±4.3; ECC 18.8±3.0%) relative to their own baseline (P<0.05). Therefore, improved leg strength was equivalent between CON and ECC groups despite the varied training (P>0.05).

CONCLUSIONS

In sedentary middle age males, eccentric endurance cycling with a low cardiovascular demand, increased both quadriceps isometric and 6RM strength comparable to a matched workload concentric cycling program.

Effectiveness of a Home-Based Eccentric-Exercise Program on the Torque-Angle Relationship of the Shoulder External Rotators: A Pilot Study

CONTEXT

The role of the rotator cuff is to provide dynamic stability to the glenohumeral joint. Human and animal studies have identified sarcomerogenesis as an outcome of eccentric training indicated by more torque generation with the muscle in a lengthened position.

OBJECTIVE

The authors hypothesized that a home-based eccentric-exercise program could increase the shoulder external rotators' eccentric strength at terminal internal rotation (IR).

DESIGN

Prospective case series.

SETTING

Clinical laboratory and home exercising.

PARTICIPANTS

10 healthy subjects (age 30 ± 10 y).

INTERVENTION

All participants performed 2 eccentric exercises targeting the posterior shoulder for 6 wk using a home-based intervention program using side-lying external rotation (ER) and horizontal abduction.

MAIN OUTCOME MEASURES

Dynamic eccentric shoulder strength measured at 60°/s through a 100° arc divided into 4 equal 25° arcs (ER 50-25°, ER 25-0°, IR 0-25°, IR 25-50°) to measure angular impulse to represent the work performed. In addition, isometric shoulder ER was measured at 5 points throughout the arc of motion (45° IR, 30° IR, 15° IR, 0°, and 15° ER). Comparison of isometric and dynamic strength from pre- to posttesting was evaluated with a repeated-measure ANOVA using time and arc or positions as within factors.

RESULTS

The isometric force measures revealed no significant differences between the 5 positions (P = .56). Analysis of the dynamic eccentric data revealed a significant difference between arcs (P = .02). The percentage-change score of the arc of IR 25-50° was found to be significantly greater than that of the arc of IR 0-25° (P = .007).

CONCLUSION

After eccentric training the only arc of motion that had a positive improvement in the capacity to absorb eccentric loads was the arc of motion that represented eccentric contractions at the longest muscle length.

Back to the future! Revisiting the physiological cost of negative work as a team-based activity for exercise physiology students

We implemented a team-based activity in our exercise physiology teaching laboratory that was inspired from Abbott et al.'s classic 1952 Journal of Physiology paper titled "The physiological cost of negative work." Abbott et al. connected two bicycles via one chain. One person cycled forward (muscle shortening contractions, positive work) while the other resisted the reverse moving pedals (muscle lengthening contractions, negative work), and the cost of work was compared. This study was the first to link human whole body energetics with isolated muscle force-velocity characteristics. The laboratory activity for our students (n = 35) was designed to reenact Abbott et al.'s experiment, integrate previously learned techniques, and illustrate differences in physiological responses to muscle shortening and lengthening contractions. Students (11-12 students/laboratory section) were split into two teams (positive work vs. negative work). One student from each team volunteered to cycle against the other for ~10 min. The remaining students in each team were tasked with measuring: 1) O₂ consumption, 2) heart rate, 3) blood lactate, and 4) perceived exertion. Students discovered that O₂ consumption during negative work was about one-half that of positive work and all other physiological parameters were also substantially lower. Muscle lengthening contractions were discussed and applied to rehabilitation and sport training. The majority of students (>90%) agreed or strongly agreed that they stayed engaged during the activity and it improved their understanding of exercise physiology. All students recommended the activity be performed again. This activity was engaging, emphasized teamwork, yielded clear results, was well received, and preserved the history of classic physiological experiments.

Moderate Load Eccentric Exercise; A Distinct Novel Training Modality

Over the last 20 years a number of studies have been published using progressive eccentric exercise protocols on motorized ergometers or similar devices that allow for controlled application of eccentric loads. Exercise protocols ramp eccentric loads over an initial 3 weeks period in order to prevent muscle damage and delayed onset muscle soreness. Final training loads reach 400-500 W in rehabilitative settings and over 1200 W in elite athletes. Training is typically carried out three times per week for durations of 20-30 min. This type of training has been characterizes as moderate load eccentric exercise. It has also been denoted RENEW (Resistance Exercise via Negative Eccentric Work by LaStayo et al., 2014). It is distinct from plyometric exercises (i.e., drop jumps) that impose muscle loads of several thousand Watts on muscles and tendons. It is also distinct from eccentric overload training whereby loads in a conventional strength training setting are increased in the eccentric phase of the movement to match concentric loads. Moderate load eccentric exercise (or RENEW) has been shown to be similarly effective as conventional strength training in increasing muscle strength and muscle volume. However, as carried out at higher angular velocities of joint movement, it reduces joint loads. A hallmark of moderate load eccentric exercise is the fact that the energy requirements are typically 4-fold smaller than in concentric exercise of the same load. This makes moderate load eccentric exercise training the tool of choice in medical conditions with limitations in muscle energy supply. The use and effectiveness of moderate load eccentric exercise has been demonstrated mostly in small scale studies for cardiorespiratory conditions, sarcopenia of old age, cancer, diabetes type 2, and neurological conditions. It has also been used effectively in the prevention and rehabilitation of injuries of the locomotor system in particular the rehabilitation after anterior cruciate ligament surgery.