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The peripheral adaptation process associated with repeating eccentric training over a longer period of time was studied in m. vastus lateralis of eleven healthy males aged 24 +/- 4 years. The maximal dynamic concentric muscle strength was only slightly improved after 8 weeks of training. However, eccentric work capacity was dramatically increased (375%). A maximal eccentric stint immediately after fulfilled 8 weeks of training caused a selective glycogen depletion from the type 28 fibers. An increased number of type 2C fibers was observed. The ultrastructure analysis showed an essentially well-preserved fine structure. Volume density of mitochondria was somewhat higher in all fiber types after training. Z-band widths were not affected by eccentric training. It is concluded that skeletal musculature adapts itself in a functional manner to the extreme tension demands put on them. Improved coordination and reorganization of the contractile apparatus of muscle fibers are the determining mechanisms of this adaptation.

1. Increases in strength and size of the quadriceps muscle have been compared during 12 weeks of either isometric or dynamic strength training. 2. Isometric training of one leg resulted in a significant increase in force (35 +/- 19%, mean +/- S.D., n = 6) with no change in the contralateral untrained control leg. 3. Quadriceps cross-sectional area was measured from mid-thigh X-ray computerized tomography (c.t.) scans before and after training. The increase in area (5 +/- 4.6%, mean +/- S.D., n = 6) was smaller than, and not correlated with, the increase in strength. 4. The possibility that the stimulus for gain in strength is the high force developed in the muscle was examined by comparing two training regimes, one where the muscle shortened (concentric) and the other where the muscle was stretched (eccentric) during the training exercise. Forces generated during eccentric training were 45% higher than during concentric training. 5. Similar changes in strength and muscle cross-sectional area were found after the two forms of exercise. Eccentric exercise increased isometric force by 11 +/- 3.6% (mean +/- S.D., n = 6), and concentric training by 15 +/- 8.0% (mean +/- S.D., n = 6). In both cases there was an approximate 5% increase in cross-sectional area. 6. It is concluded that as a result of strength training the main change in the first 12 weeks is an increase in the force generated per unit cross-sectional area of muscle. The stimulus for this is unknown but comparison of the effects of eccentric and concentric training suggest it is unlikely to be solely mechanical stress or metabolic fluxes in the muscle.

This research was supported by a Duke University Research Council Grant. The purpose of this study was to examine mode and speed specificity of strength training by comparing concentric and eccentric isokinetic exercise of the quadriceps. Forty-eight healthy men (mean age = 23.9 years) were randomly assigned to one of three groups: concentric training (C), eccentric training (E), or control (K). Average force (in Newtons) of 3 concentric and of 3 eccentric quadriceps contractions on the KIN-COM(R) dynamometer at 60, 120, and 180 degrees /sec was evaluated prior to and following a 6 week period during which only the C and E groups trained. Training sessions (3/week) included 4 submaximal and 1 maximal warm-up followed by 10 maximal effort isokinetic contractions of the quadriceps at 120 degrees /sec for each leg. Group C subjects trained concentrically only while Group E subjects trained eccentrically only. A t-test for independent means showed no significant right/left differences. ANOVA and Scheffe's F-tests were then used to assess the differences in training effects among the 3 groups for the left leg only. Results showed that although Group C increased slightly in both concentric and eccentric force at all speeds, the gains were significant only for concentric force at 180 degrees /sec. Group E showed significant gains (p0.05) in eccentric force at all speeds but not in concentric force. The K group had no significant change in concentric or eccentric force at any speed. We conclude that the eccentric mode of isokinetic exercise has highly specific strength training effects while the concentric mode has less specific training effects. In addition, speed of exercise does not appear to have specific training effects. J Orthop Sports Phys Ther 1989;11(2):70-75.

BackgroundThe standard method to treat physically active patients with anterior cruciate ligament (ACL) rupture is ligament reconstruction surgery. The rehabilitation training program is very important to improve functional performance in recreational athletes following ACL reconstruction.ObjectivesThe aims of this study were to compare the effects of three different training programs, eccentric training (ECC), plyometric training (PLYO), or combined eccentric and plyometric training (COMB), on dynamic balance (Y-BAL), the Lysholm Knee Scale (LKS), the return to sport index (RSI), and the leg symmetry index (LSI) for the single leg hop test for distance in elite female athletes after ACL surgery.Materials and MethodsFourteen weeks after rehabilitation from surgery, 40 elite female athletes (20.3 ± 3.2 years), who had undergone an ACL reconstruction, participated in a short-term (6 weeks; two times a week) training study. All participants received the same rehabilitation protocol prior to the training study. Athletes were randomly assigned to three experimental groups, ECC (n= 10), PLYO (n= 10), and COMB (n= 10), and to a control group (CON:n= 10). Testing was conducted before and after the 6-week training programs and included the Y-BAL, LKS, and RSI. LSI was assessed after the 6-week training programs only.ResultsAdherence rate was 100% across all groups and no training or test-related injuries were reported. No significant between-group baseline differences (pre-6-week training) were observed for any of the parameters. Significant group-by-time interactions were found for Y-BAL (p< 0.001, ES = 1.73), LKS (p< 0.001, ES = 0.76), and RSI (p< 0.001, ES = 1.39). Contrast analysis demonstrated that COMB yielded significantly greater improvements in Y-BAL, LKS, and RSI (allp< 0.001), in addition to significantly better performances in LSI (allp< 0.001), than CON, PLYO, and ECC, respectively.ConclusionIn conclusion, combined (eccentric/plyometric) training seems to represent the most effective training method as it exerts positive effects on both stability and functional performance in the post-ACL-surgical rehabilitation period of elite female athletes.

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.

The aim of the study was to show that the addition of extracorporeal shockwave therapy (ESWT) may significantly improve beneficial effects of eccentric training together with high efficiency focused acoustic waves for jumper's knee. We speculate that such an effect may be due to increased mechanotransduction effects on affected tissues. We assessed changes in pain and function in 42 male football players (aged 1834 years) after a treatment protocol consisting of I session with focused ESWT per week combined with 3 physiotherapy sessions per week, for 3 consecutive weeks. While treatment protocol was administered, ordinary activities, but not playing football were permitted. Their condition was evaluated before treatment, at the end of the rehabilitation period (3 weeks) and at 2 months, 4 months and 6 months after the end of treatment by clinical examination, instrumental analysis and VAS for pain assessment. Functional ability related to symptoms was assessed with VISA score. At the end of 2005,2006,2007,2008 and 2009 we carried out a telephone interview to investigate changes in pain and function and the efficacy of the treatment over time. Follow-up controls showed a reduction of average VAS score; after 6 months, tendons showed a structure closer to normal at ultrasonographic investigation. At the last telephone interview in 2009 many patients reported to consider ESWT as an effective treatment and described a significant improvement in their functional abilities, a significant reduction in drug consumption and 88% of subjects continued to play agonistic football. In conclusion, our results showed that, through the addition of ESWT, the effects of the classic vibration and eccentric training combination were improved compared to those found in our experience without ESWT. Although a control group was not included in the study (vibration and eccentric training without ESWT), results show a promising improvement and justify future prospective studies with a control group and more case series.

The aims of this study were to examine two ski simulators, Skimagic and Skier's Edge, and to evaluate their efficacy as functional training devices for skiers. Vertical ground reaction forces, knee flexion angle kinematics and muscles activity were recorded on these devices and compared with those measured in similar condition while skiing on snow. Five ski instructors performed three randomized testing sessions (snow, Skimagic and Skier's Edge). During the testing sessions, vertical ground reaction forces were recorded by means of pressure insoles in synchronisation with a portable data logger that collected values of knee flexion-extension and EMG activation of rectus femoris and vastus medialis. EMG activations and ground reaction forces measured while skiing on simulators were lower than on snow. Although less overall EMG activation was present on the simulators, the pattern of EMG activity was closer to real snow on Skimagic than on Skiers' Edge. Results of the present study suggested that the two devices are not effectively applicable for strength training. However, based on the recorded EMG patterns, the Skimagic treadmill is potentially suitable to act as a functional training device for recreational skiers provided that an increase of speed and slope on Skimagic could induce a closer matching of the studied biomechanical parameters with the snow skiing conditions. Key pointsEMG activation and ground reaction forces were lower on both simulators with respect to snow.Both simulators were not able to provide an effective contribution to strength development for skiers.In term of functional training Skier's Edge showed a predominance of concentric action over eccentric which is in contrast with competitive skiing.Skimagic treadmill could be potentially suitable to act as a functional training device for recreational skiers only if an increase of speed and slope will induce a closer matching of the studied biomechanical parameters with the snow skiing conditions.

Eccentric loading is an effective stimulus for muscle hypertrophy and strength gains, however, the effect of lengthening velocity is under debate. The purpose of the current study was to investigate the influence of muscle lengthening velocity during eccentric training on muscle hypertrophy and strength gains at a given overall loading volume. Forty-seven participants were randomly assigned to a control (n = 14, age: 26.9 ± 4.1 years) and an experimental group (n = 33, age: 27.1 ± 4.4 years). Each leg of the participants in the experimental group was randomly assigned to one of the four eccentric training protocols with different angular velocities (i.e., 45, 120, 210, and 300°/s). Both the magnitude of loading (100% of the isometric maximum) and overall time under tension was matched between the protocols. The training was performed for 33 sessions, 3 times per week with 5 training sets per session. Before and after the intervention, the maximum isometric knee extension moments were measured in all groups using dynamometry, vastus lateralis (VL) muscle anatomical cross-sectional area, and VL muscle volume were measured in the experimental group using magnetic resonance imaging. Data was analyzed in a mixed-design analysis of variance. After the training intervention, the maximum knee joint moments increased in the experimental group (14.2%, p 0.05). The present study provides evidence that muscle hypertrophy and strength gains after eccentric exercise is velocity-independent when load magnitude and overall time under tension are matched between conditions. This is likely due to the similar mechanical demand for the muscle induced by the loading conditions of all four training protocols. The better control of motion and the potentially decreased joint loading compared to high lengthening velocity contractions support the application of slow eccentric exercises in special populations like elderly and people with neurological and musculoskeletal diseases.

Objective: To examine the effects of combining whey protein isolate supplement with preoperative isokinetic eccentric training on quadriceps mass and strength following anterior cruciate ligament rupture. Design: Randomized controlled trial. Subjects: A total of 37 male subjects with anterior cruciate ligament rupture. Methods: Participants were randomly assigned to an isokinetic eccentric training group (n = 19) or an isokinetic eccentric training + whey protein isolate group (n = 18). Both groups received isokinetic eccentric training for 6 weeks. The isokinetic eccentric training + whey protein isolate group received 22 g whey protein isolate daily. Results: After the intervention, the cross-sectional area of the affected quadriceps had increased only in the isokinetic eccentric training + whey protein isolate group (7.6 ± 6.8%; p = 0.012), whereas there was no change in the isokinetic eccentric training group (3.7 ± 4.5%; p = 0.11). Both groups showed increased quadriceps strength; however, there were no further effects for the isokinetic eccentric training + whey protein isolate group. Lysholm and IKDC 2000 knee function scores increased only in the isokinetic eccentric training + whey protein isolate group (p

Eight male university students served as subjects in an investigation designed to develop strength using two different muscle training routines over a six week period. The subjects trained the arm and leg on one side of their bodies using concentric contractions and the arm and leg on the opposite side of their bodies with identical exercises using eccentric contractions. Concentric movements were against a resistance 80% of one-repetition-maximum (1-Rm) for 10 repetitions and two sets; eccentric movements were against a force of 120% of concentric 1-RM for 6 repetitions and two sets. Both routines produced significant gains in strength in all subjects, but neither training procedure produced dynamic or static strength gains significantly different from the other. Subjective evaluations by the subjects indicated that the eccentric training movements were easier to perform than the concentric training movements.

Objectives To evaluate, in chronic heart failure (CHF) patients, feasibility, safety, compliance and functional improvements of an eccentric (ECC) cycle training protocol personalized by the rate of perceived exertion (RPE; 9–11 Borg Scale), compared to concentric (CON) training at workload corresponding to the first ventilatory threshold. Methods Thirty patients were randomly allocated to ECC or CON training (20 sessions). Compliance was evaluated with RPE, visual analog scale for muscle soreness and monitoring of heart rate (HR). Functional parameters were measured by the distance walked and the VO 2 uptake during the 6-minute walk test (6MWT) before and after training. Results Two patients were excluded due to adverse effects in each group. RPE was 9–11 in ECC training while it reached 12–14 in CON training. HR remained stable in ECC group during exercise whereas it increased during CON exercise. 6MWT distance improved in both group (ECC: +53 m; CON: +33 m). 6MWT VO 2 uptake remained stable in ECC group whereas it increased in CON group. Conclusion ECC training tailored by RPE appears to be an efficient and safe alternative for CHF patients. Indeed, it induces functional improvement similar to conventional CON training with lower demand on the cardiovascular system during exercise.