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The Effects of Eccentric Strength Training on Flexibility and Strength in Healthy Samples and Laboratory Settings: A Systematic Review

Vetter, S., Schleichardt, A., Köhler, H.P. and Witt, M., 2022. The effects of eccentric strength training on flexibility and strength in healthy samples and laboratory settings: A systematic review. Frontiers in Physiology, 13, p.873370.

In today’s letter

• Overview of the study looking at eccentric training and its effects on range of motion & strength

• Rapid Results = There is high evidence showing that eccentric training is a highly effective approach for altering muscle architecture, resulting in better outcomes in both lower limb flexibility and strength

• 3 Reads to check out to further you knowledge about eccentric training

• Meme of the week: Just one more set? 🥲 

Aim of study

The aim of this review is to investigate whether eccentric exercise is capable of improving both strength and flexibility within highly standardised settings

Did you know?

• High-performance sports demands a lot from your body due to frequent training and limited recovery

• Prolonged exposure to such stressors often results in degeneration, lesions, and injuries affecting both upper and lower body joints.

• While strength training is commonly linked with performance enhancement, flexibility training primarily helps in recovery and is often overlooked in athletes' schedules.

• Effective athletic training should target both flexibility and strength simultaneously to optimise time management, minimise injury risks, and prevent training interruptions.

• The muscle-tendon unit contributes to 51% to joint flexibility, which is why its important for both performance and injury prevention.

• Common prevention and rehabilitation methods include static stretching and concentric training.

• Neither stretching nor concentric training has shown evidence of fascicle lengthening in lower limb testing

• Reduced fascicle length is associated with increased injury risk, suggesting stretching may not be suitable for injury prevention.

• Eccentric training for the lower limb aims to increase flexibility, increase fascicle length, and enhance isokinetic torque performance

Torque performance = it measures the strength of a muscle when it contracts at a consistent rate of movement

• Eccentric training's impact on muscular excursion range and eccentric torque may lead to improved motor performance and reduced injury risk.

• Eccentric training also enhances muscular energy absorption, buffering surrounding structures after intense training sessions

• Existing systematic reviews and meta-analyses primarily focus on the lower limb and lack comprehensive assessment of existing flexibility and strength effects.

• Many studies on flexibility strength training suffer from low methodological quality and produce conflicting results.

Results

Total of 18 studies met all inclusion criteria

Characteristics of Eccentric Training

• Training protocols varied significantly across studies, with 13 studies comparing the effects of a training group against a non-training control group.

• Among these, 11 studies included multiple training groups, with 6 studies featuring a comparison against concentric training and 4 studies comparing different eccentric protocols.

• Seven out of 18 studies used an isokinetic dynamometer for participant training.

• Additionally, 7 studies implemented various eccentric field exercises.

• The average duration of interventions was 7.1 ± 2 weeks, spanning from 4 to 10 weeks.

• Only 3 studies had interventions lasting less than 6 weeks.

• On average, the number of sets per session was 4.5 ± 1.2, with a minimum of 2 sets and a maximum of 6 sets.

• Repetitions per set averaged at 9.1 ± 2.8, ranging from 5 to 16 repetitions.

• Training intensity varied widely, from 40% to at least 100% of the concentric one-repetition maximum (1RM).

Methodological Quality

Eccentric Strength

• 18 eccentric training subgroups were tested for eccentric strength, 3 groups without significant changes

• Simple pooled analysis of 15 eccentric training subgroups showed an average improvement of +19 ± 10% of eccentric strength. 4 subgroups with concentric training revealed +19 ± 11% improvement

Concentric Strength

• Concentric strength values were reported for 12 eccentric training subgroups, 6 of which showed no significant changes

• 11 eccentric training subgroups were used for simple pooled analysis

• After eccentric training, concentric strength improved by +9 ± 6%.

• 3 concentric training groups showed an mean improvement of +16 ± 7%

• For the simple pooled analysis, 11 eccentric training subgroups were included - eccentric training improved concentric strength by +16 ± 10%.

Isometric Strength

• All of 15 eccentric training groups revealed isometric strength gains. Results varied between +5.9% and a significant gain of +44% after eccentric training.

• In contrast, the maximum improvement in isometric strength after concentric training was +20.4%

Pennation Angle

Pennation angle = The pennation angle represents the angle between muscle fibers and the direction of force generation.

Muscles with a larger pennation angle generally have a greater ability to generate force because the muscle fibers are arranged in a way that allows for more cross-sectional area and thus more force-producing capacity

• Pennation angle values were reported for 15 eccentric training subgroups, 7 of which showed no significant changes

• 14 eccentric training subgroups were used for simple pooled analysis After eccentric training the average angular change in Pennation angle was +5 ± 7%.

• In comparison, 5 concentric training subgroups showed an average Pennation angle change of +15 ± 11%

Passive Range of Motion

• 7 subgroups were tested for range of motion, 1 of which showed no significant changes Results ranged from −19.6% up to +12.7% improvement

• Simple pooled analysis of 6 eccentric training subgroups showed an average range of motion improvement of +9 ± 7%

Muscle Fascicle Length

• Fascicle length values were reported for 21 subgroups, 7 of which showed no significant changes

• Results ranged from a non-significant result of −3% to a significant improvement of Fascicle length by +33.5%

• Simple pooled analysis revealed an average gain of Fascicle length by +10 ± 9% for 16 eccentric training subgroups 5 concentric training showed an average change of −1 ± 8%

Discussion

Main Findings

• 17 out of 18 studies demonstrated significant enhancements in at least one strength measure, while 16 out of 18 studies showed improvements in at least one flexibility measure following eccentric training

• A basic combined analysis of eccentric training outcomes indicated overall positive changes, including:

1. +19% increase in eccentric strength

2. +9% in concentric strength, +10% in fascicle length

3. +9% in range of motion

• On the other hand, concentric training showed improvements in eccentric (19%) and notably larger effects in concentric (16%) strength but failed to enhance Fascicle length (−1%).

• Hence, evidence suggests that eccentric training effectively enhances both flexibility and strength parameters by integrating the benefits of strengthening and stretching interventions into a single exercise.

Interpretation of Results

• The review highlights significant advantages of eccentric training over concentric training, particularly in inducing improvements in range of motion (ROM).

• While strength gains between eccentric training and concentric training are similar, eccentric training results in substantially larger increases in ROM compared

• Studies comparing eccentric training to various stretching exercises show that ROM enhancement are comparable to ballistic stretching (11%) but lesser than static stretching (18–21%).

• Eccentric training , by simultaneously impacting both stretching and strength, offers 2-fold benefits, which enhancing training efficiency.

• Unique to eccentric training is the fascicle lengthening, not observed in oncentric training or stretching exercises.

• Eccentric training effects can be attributed to several mechanisms, with sarcomerogenesis being crucial for improving the torque-angle relationship.

• Sarcomerogenesis involves longitudinal hypertrophy of muscular fascicles, occurring after repeated overstretching followed by reconstruction and addition of new sarcomeres to prevent muscle trauma within the newly attained ROM.

• Positive changes in fascicle length correlate closely with shifts in the torque-angle relationship, as demonstrated in studies focusing on the vastus lateralis.

• Further evidence supports the positive association between sprinting performance and fascicle length.

• Eccentric training , which combine stretching and strengthening, appear to be highly effective in simultaneously enhancing strength and flexibility.

Top 3 resources:

To further you understanding of eccentric training

1. A guide to eccentric training

   https://www.sportsmith.co/articles/an-essential-guide-to-eccentric-training/

2. Periodise eccentric training in season

   https://journal.iusca.org/index.php/Journal/article/view/151/224

3. VIDEO: Eccentric hamstring strength in team sports

   https://www.uksca.org.uk/uksca-iq/article/2048/resistance-training/eccentric-hamstring-strength-and-sagittal-plane-lower-limb-running-kinematics-across-team-sports

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