ANATOMIE DES MUSCLES ET TENDONS

Name: ANATOMIE DES MUSCLES ET TENDONS
Uploaded: 2024-03-19T14:09:46.000Z
Duration: 2 h 16 min 10 s

Welcome and Introduction

Opening Remarks

The speaker welcomes students, research teams, and the French Federation of Rugby to the conference organized by the laboratory in conjunction with this year's Olympic and Paralympic events.

Acknowledgment is given to Antonio Morales for his contributions, with a note on changes to the conference format focusing on expert presentations rather than larger events due to upcoming Olympic preparations.

Speaker Introduction

Jonathan Folland is introduced as a professor at the University of Lovebro, noted for his expertise in biomechanics and physiology.

Folland's affiliations include membership in the American College of Sports Medicine and the Royal Society of Biology; he also co-directs a research center focused on arthrosis.

Research Focus

Areas of Expertise

Folland has experience advising various organizations including Technogym and British Athletics, emphasizing his dual focus on clinical research and applied performance training.

His research primarily investigates physical performance, muscle strength, power functions, and their implications across different sports contexts.

Recent Work

Discussion includes recent publications related to high-end muscle function that have applications in performance enhancement, injury prevention, and health maintenance.

Contextualization of Presentation

Overview by Antonio Morales

Antonio begins contextualizing Jonathan's presentation while switching to English for broader accessibility. He invites questions from attendees regardless of language preference.

Importance of Muscle Strength Research

Emphasis is placed on understanding muscle strength not only from mechanistic perspectives but also its critical role in optimizing athletic performance.

Training Interventions

Methodological Insights

Discussion highlights basic questions regarding force production and tissue interaction that are central to translating research into practical applications.

Training Study Example

An eight-week training intervention involving Nordic hamstring exercises is mentioned; ultrasonography was used to measure muscle fascicle behavior during this study.

Advanced Techniques

The use of elastography is introduced as a method for assessing mechanical properties during passive cycles within hamstring muscles.

Muscle-Tendon Unit Mechanics and Research Insights

Exploring Passive Mechanical Properties

The discussion begins with an exploration of passive mechanical properties, including concepts like the John modulus and hysteresis at a local muscle level.

Effects of Warm-Up Techniques

A study conducted in the lab examined the effects of different warm-up techniques (foam rolling vs. cycling) on the elastic properties of hamstrings, highlighting variations in research topics.

Surface Interaction Studies

Enzo Lville's PhD work focused on how muscles and tendons interact when working on various surfaces, providing insights into their responses under different conditions.

Heat Exposure Impact

Adele Mornas' research during her PhD investigated how heat exposure affects active and passive elements of muscle-tendon units during tasks such as running, contributing to recent findings published in a scientific journal.

Technological Advances in Measurement

The speaker emphasizes that while technology presents challenges in measuring muscle-tendon properties in vivo, advancements like elastography are helping overcome limitations by moving from 2D to 3D approaches for better understanding muscle behavior.

The Role of AI and Engineering in Muscle Analysis

Automation in MRI Segmentation

Current MRI techniques are time-consuming due to manual segmentation; however, ongoing AI developments aim to streamline this process for more efficient analysis of muscle architecture.

Broader Research Scope at INSEP

The speaker notes that INSEP considers various factors within sports science beyond just experimental research, aiming for comprehensive integration across disciplines. This is illustrated through a representative image shared during the talk.

Introduction to Loughborough University and Its Reputation

Personal Connection to Canoeing

Jonathan shares his long-standing interest in canoeing and kayaking, mentioning his excitement about visiting INSEP after hearing about it as a teenager due to its association with top athletes.

Overview of Loughborough University

He introduces Loughborough University as a mid-sized institution known for its strong reputation in sports-related studies, ranking highly among UK universities with around 20,000 students on a green campus equipped with extensive sports facilities.

Muscle Anatomy: Importance for Performance and Injury Risk

Themes Addressed

Jonathan outlines three main themes:

The significance of muscle anatomy (especially size) for athletic performance.

Hamstring anatomy's implications regarding sports injuries.

Effects of resistance training on muscle-tendon structures.

Perception of Muscle Strength

He humorously poses a question about who has the strongest muscles based on appearance, noting that people often associate larger muscles with greater strength—a common misconception he plans to address further along in his presentation.

Muscle Size and Strength: Insights from Scientific Studies

Physiological Foundations of Muscle Strength

The relationship between muscle size and strength is grounded in physiological principles, highlighted by a 1968 study from Japan measuring elbow flexor muscle size and its correlation with strength.

A broad relationship exists where individuals with larger muscles tend to exhibit greater strength, explained by the number of cross bridges or sarcomeres arranged in parallel within the muscle.

Increased contractile material (sarcomeres/cross bridges) leads to enhanced force production; larger muscles can generate more force due to this arrangement.

Despite understanding these concepts for decades, there remains limited knowledge about the anatomy and size of high-performing athletes' muscles and their impact on athletic performance.

Study on Muscle Anatomy and Cycling Power

A series of studies were conducted to explore muscle anatomy's role in sprint cycling power, collaborating with the English Institute of Sport.

The study involved 35 elite male cyclists across various disciplines, showcasing their impressive performance credentials including Olympic appearances and world championship medals.

Athletes performed ISO velocity sprints at varying speeds on an ergometer, allowing researchers to establish a power-cadence relationship for each participant.

MRI scans measured thigh muscle volume (quadriceps and hamstrings), providing detailed anatomical data crucial for analyzing performance outcomes.

Findings on Muscle Volume and Power Output

Results indicated a strong correlation (0.81 coefficient) between quadriceps muscle volume and peak power output during cycling; hamstrings showed a slightly weaker correlation (0.72).

The conclusion emphasized that quadriceps volume is a primary determinant of cycling peak power output, critical for sprint cycling performance.

Notably, while ergometer power output is relevant, it does not directly equate to actual competitive performance metrics among athletes.

Next Steps: Investigating Sprint Running Performance

Future studies shifted focus towards sprint running performance in collaboration with British athletics, recognizing elite sprinting as a significant aspect of human athleticism.

Fast running ability is essential across various sports beyond track athletics; however, specific muscular contributions to speed have been inadequately defined in prior research.

Observations from animal physiology suggest that successful land mammals possess proximal rather than distal muscle mass distribution—insights that could inform future studies on human sprinters.

Muscle Development in Elite Sprinters

Hypothesis and Study Overview

Our hypothesis posits that elite human sprinters exhibit specific muscular development concentrated around the hip joint.

Two separate studies were conducted: one focusing on males and another on females, employing similar methodologies to compare results.

Male Study Results

The male study compared elite sprinters (personal best under 10 seconds) with sub-elite sprinters (average time of 10.6 seconds) and untrained controls.

A small group of elite sprinters was analyzed due to the rarity of individuals capable of such fast times.

MRI scans were performed from thoracic vertebra number 12 down to the ankle, measuring muscle volume across 23 individual muscles or compartments.

Muscle Volume Findings

Muscle volume data was expressed both in absolute terms (cubic centimeters) and relative to body mass; however, absolute units were used for clarity in presentation.

Significant differences were observed in hip extensor volumes among groups: untrained controls had about 2000 cc, while sub-elite and elite sprinters had approximately a third more muscle volume each.

Female Study Results

In the female study, only elite and sub-elite sprinter groups were included due to prior findings indicating notable differences between these two categories.

The most significant difference was found in hip flexor volumes, which were 28% larger in elite versus sub-elite female sprinters; no differences existed for plantar flexors across both genders.

Visual Evidence of Muscle Differences

MRI images illustrated clear visual distinctions between muscle sizes in sub-elite versus elite sprinters, particularly around the hips and pelvis area.

The gluteus maximus showed dramatic size increases: averaging around 900 cc for untrained participants compared to nearly 1800 cc for elite sprinters—equivalent to two large steaks per buttock!

Summary of Individual Muscle Differences

A detailed plot presented percentage differences between elite and sub-elites across various muscles, highlighting that zero indicates equal volume while positive values indicate greater size in elites.

Muscle Differences in Elite vs. Subelite Sprinters

Overview of Muscle Differences

The ranking of muscles shows significant differences between elite and subelite sprinters, with the largest differences favoring elite athletes.

Female sprinters exhibit similar patterns in muscularity, indicating a consistent trend across genders regarding muscle size differences.

Anatomical Specificity in Muscularity

A pronounced pattern exists in muscular development among sprinters; not all muscles are uniformly larger, highlighting specific anatomical adaptations.

Two studies reveal that three key muscles—tensor fasciae latae, sartorius, and gluteus maximus—show the most significant size differences between male and female sprinters.

Key Muscles and Their Functions

The sartorius is unique as it functions as both a hip and knee flexor during the swing phase of running, crucial for rapid limb movement.

The gluteus maximus plays a vital role in generating high leg momentum during late swing phases, aiding in effective ground contact for propulsion.

Evolutionary Significance of Gluteus Maximus

As the largest muscle in the human body, the gluteus maximus may have evolved to enhance running speed through its biomechanical advantages.

Correlations show that gluteus maximus size significantly impacts 100m sprint performance, explaining up to 43% of variability among athletes.

Implications for Training

Understanding these muscle characteristics suggests that training should be anatomically targeted rather than generalized to improve athletic performance effectively.

Elite sprinters demonstrate distinct muscular patterns primarily involving proximal muscle groups like hip extensors and flexors critical for sprinting success.

Hamstring Anatomy and Injury Implications

Importance of Hamstrings

Hamstring injuries are prevalent in sports like football, with an average of five injuries per professional club each season.

The hamstrings stabilize the knee joint and play a crucial role in preventing severe injuries such as ACL ruptures.

Gender Differences in Injury Incidence

There are notable gender disparities in lower limb injury rates; females experience ACL injuries at rates two to ten times higher than males during agility sports.

Is There a Sex Difference in Knee Strength?

Maximum Strength Relative to Body Mass

The discussion begins with data on isometric maximum strength relative to body mass, comparing untrained females and males. It highlights that both sexes show similar scores in knee extensor strength (quadriceps).

Knee Flexor Strength Disparities

In contrast, when examining knee flexors (hamstrings), females exhibit a significant disadvantage, showing 15% lower knee flexion strength compared to males.

The hamstrings-to-quadriceps ratio, an indicator of knee joint stability and injury risk, reveals that females have a lower ratio (50%) than males (56%).

Implications for ACL Injury Risk

The lower hamstring strength may influence the stability of the knee joint, as the hamstrings help prevent anterior tibial translation—a movement linked to ACL ruptures.

An MRI study was conducted to explore whether females possess smaller hamstring muscles relative to their quadriceps.

MRI Findings on Muscle Size Ratios

Results indicate that untrained females have a disproportionately smaller size ratio of knee flexors compared to extensors than males. This could contribute to higher ACL injury rates among women.

Understanding Hamstring Structure and Injury Risks

Focus on Bicep Femoris Long Head

The presentation shifts focus to the bicep femoris long head muscle, which is commonly injured during hamstring strains.

Detailed anatomical structures are discussed, including muscle fibers and tendons; specifically how force transmission occurs through the aponeurosis rather than directly onto the tendon.

Mechanical Strain Concentration

The proximal region adjacent to the aponeurosis is identified as a common site for injuries due to concentrated mechanical strain.

Aponeurosis Size Study

A study measuring the size of the proximal aponeurosis in healthy young men revealed variability in contact area between muscle and aponeurosis using MRI techniques.

Hypothesis on Injury Predisposition

A hypothesis emerges suggesting that a smaller bicep femoris long head proximal aponeurosis may lead to concentrated mechanical stress in adjacent muscle tissue, increasing strain injury risk.

Retrospective Study on Hamstring Injuries

Athlete Recruitment for Injury Analysis

A retrospective study involved recruiting male athletes who had previously sustained multiple clinically verified strain injuries in the proximal bicep femoris long head but had returned to normal training at least three months prior.

Historical Injuries and Aponeurosis Size

Overview of Injury History

The study focuses on historical injuries among a group of 23 athletes, noting that some had bilateral injuries while others had unilateral injury histories.

Among the participants, 12 athletes had a history of injury on one leg, with the other leg remaining healthy throughout.

Analysis of Aponeurosis Size

An analysis was conducted comparing the previously injured leg to the healthy leg using two measures: maximum width and aponeurosis area.

Results indicated that both measures showed a smaller aponeurosis in the previously injured legs compared to healthy legs from a control group.

Comparison with Control Group

A total of 28 clinically verified injured legs were compared against 46 healthy legs matched for sport, age, sex, and height.

Findings confirmed that prior hamstring strain injured legs exhibited smaller aponeurosis sizes than their healthy counterparts.

Implications of Aponeurosis Size on Injury Risk

Conclusions from Retrospective Study

The study suggests that a small aponeurosis may be associated with hamstring strain injury history; however, causation cannot be established due to its retrospective nature.

Further prospective studies are needed to clarify whether small aponeurosis leads to injuries or if injuries result in reduced aponeurosis size.

Resistance Training and Tissue Adaptations

Importance of Muscle Size for Performance

Emphasizes muscle size's role in athletic performance and resilience against injuries; resistance training is highlighted as a method to increase muscle and tendon tissue size.

Study Design on Resistance Training Effects

A study involving 39 young men over 15 weeks examined muscle and tendon adaptations through resistance training combined with collagen peptide supplementation.

Findings on Strength and Muscle Volume

Isometric Strength Improvements

Both collagen peptide and placebo groups showed similar improvements in isometric strength (approximately 22%).

Quadriceps Muscle Volume Changes

Collagen peptide group demonstrated greater increases in quadriceps volume (15%) compared to placebo (10%), indicating enhanced training response.

Tendon Adaptations Post Resistance Training

Tendon Size vs. Material Properties

No significant changes were observed in patellar tendon size post-training; changes were less than 2%.

Tendon Stiffness Improvements

Patellar tendon stiffness increased significantly by approximately 21% for collagen peptides and 17% for placebo, showing no difference between groups.

Aponeurosis Response to Training

Adaptation Observations

Aponeurosis within vastus lateralis adapted positively with training but did not respond significantly to supplementation.

Need for Extended Training Duration

Suggestion that free tendons may require longer training periods for adaptation compared to other tissues.

Muscle and Tendon Adaptations in Resistance Training

Strength and Muscle Size Differences

The long-term trained group exhibited nearly 60% greater maximum voluntary torque compared to untrained controls, indicating significant isometric strength improvements.

Quadriceps volume was also notably larger, with the long-term trained group having muscles that were 56% bigger than those of untrained individuals.

Aponeurosis and Tendon Observations

A modest increase in aponeurosis size (17% larger) was observed in the vastus lateralis of the long-term trained group, suggesting adaptability to training.

Despite regular heavy weight training, the patellar tendon cross-sectional area remained identical between both groups, indicating no apparent adaptation in tendon size over time.

Conclusions on Tissue Adaptation

The study concluded that while aponeurosis size increases with medium to long-term resistance training, tendon size does not show similar adaptations. Collagen peptide supplementation may enhance muscle hypertrophy but does not affect tendon tissues significantly. Additionally, hypertrophic effects do not necessarily translate into strength gains due to other influencing factors like neural adaptations.

Insights from Eddie Hall: World's Strongest Man

Functional Testing and Measurements

Eddie Hall, a former world's strongest man and deadlift champion, underwent functional tests and MRI scans for detailed anatomical measurements about a year after his title win.

His quadriceps muscle volume was found to be approximately 213% larger than that of untrained controls, showcasing extreme muscular development.

Tendon Size Comparisons

While Hall's patellar tendon was 30% larger than that of untrained individuals, it still fell within expected ranges for large athletes; thus highlighting inherent differences rather than direct training effects.

Mechanical Leverage Advantages

Hall had a 21% greater patellar tendon moment arm compared to both untrained and long-term trained individuals, which could provide advantages for strength and power performance due to improved mechanical leverage around the knee joint.

Discussion on Muscle Morphology

Hypertrophy of Tensor Fasciae Latae (TFL)

A question arose regarding TFL hypertrophy in elite sprinters; it remains unclear why this muscle is particularly developed alongside gluteus maximus during sprinting phases despite its smaller size and perceived lesser importance. Possible stabilization roles for the iliotibial band were suggested as an explanation.

Proximal Aponeurosis Measurement Inquiry

An inquiry about measuring proximal aponeurosis in elite athletes highlighted that while adaptations occur slowly relative to muscle growth, increasing aponeurosis size could help manage mechanical stress during force transmission effectively. This suggests ongoing research potential in understanding these dynamics better.

Understanding Muscle Adaptation and Performance

The Relationship Between Muscle Growth and Injury Risk

Discussion on how muscle growth can lead to disproportionate development compared to the aponeurosis, potentially creating issues despite increased strength.

Noted that while the bicep femoris long head adapts with training, it does so at a lesser rate than muscle growth, which is counterintuitive regarding injury risk reduction.

Gluteus Muscles and Athletic Performance

Inquiry into the role of gluteus muscles in performance, particularly in relation to athletes with different morphological characteristics (e.g., sprinters vs. rugby players).

Open question about whether there is a ceiling for muscle mass and strength in enhancing performance; uncertainty remains.

Force Transmission and Muscle Size

Examination of common anatomical traits among sprinters that enhance force transmission to the ground, questioning the utility of large gluteus maximus muscles without this ability.

Debate over absolute versus relative muscle volume values; findings suggest absolute volumes may hold significance contrary to traditional beliefs.

Insights on Elite Sprinter Characteristics

Observation that elite male sprinters tend to be taller and larger on average, implying that absolute size may contribute positively to sprinting performance.

Acknowledgment of variability among sprinters' sizes but noting a trend towards larger body types among elite performers.

Data Interpretation Challenges

Discussion on data dispersion related to gluteus maximus size and sprinting speed; difficulty in determining if observed patterns are systematic or coincidental.

Recognition of pronounced gluteal development in assessed male sprinters but caution due to small sample size affecting conclusions.