Series: The Real Cost: The Body After Pharmacology - Episode 9: Tendons, Ligaments and the Imbalance Between Muscle and Connective Tissue

When strength increases, it is tempting to view muscle as the main engine of performance. But muscular force must be transmitted through tendons to bone, while joints are stabilized by ligaments and the rest of the connective-tissue system. A stronger engine is of limited value if the transmission does not adapt at the same pace.

In the context of performance pharmacology, this difference in adaptation rate becomes important. AAS can accelerate gains in muscle mass and strength, while collagen remodeling and changes in tendon mechanical properties occur more slowly. The possible result is a gap between what muscle can produce and what the force-transmitting system can tolerate.

This episode separates what is well supported by evidence from what remains a hypothesis. Human evidence is stronger for tendons and for the association between AAS use and tendon rupture than it is for ligaments, and the precise mechanisms remain incompletely defined.

1. Connective tissue is not a simple rope

A tendon is living tissue whose cells can detect mechanical loading and remodel the extracellular matrix. It transmits force, stores elastic energy and contributes to movement control. When its properties change, the way force reaches the joint changes as well.

2. Tendons and ligaments are not the same structure

Tendons connect muscle to bone, whereas ligaments connect bone to bone and help limit excessive joint motion. Both are collagen-rich, but they differ in architecture, vascularity, loading patterns and healing capacity. Findings about tendons should not automatically be extrapolated to ligaments.

3. Muscle and tendon adapt at different speeds

Muscle can increase relatively quickly in size and force-producing capacity. Tendon adapts too, but collagen remodeling, stiffness changes and increases in cross-sectional area occur on a slower timescale. This gap is central to understanding the mechanical imbalance.

4. Type I collagen is the mechanical backbone of tendon

Much of a tendon's tensile resistance comes from hierarchically organized type I collagen bundles. The fibers are oriented to tolerate repeated tension, and the quality of their organization matters as much as the simple amount of collagen present.

5. Tenocytes are the sensors and builders of the matrix

Tendon cells respond to mechanical loading by changing synthesis and breakdown of extracellular-matrix components. Adaptation is dynamic rather than passive reinforcement. Too little loading and excessive loading can both create problems, although through different mechanisms.

6. Collagen turnover is slow

Contractile muscle proteins can respond quickly to training and anabolic signaling, while the tendon matrix turns over more slowly. Rapid performance gains therefore do not guarantee proportional maturation of connective tissue. The feeling of strength can outpace the biological infrastructure.

7. Tendon stiffness does not automatically mean absolute strength

A stiffer tendon elongates less under a given force and can improve force transmission. Yet stiffness, elastic modulus, cross-sectional area and ultimate failure strength are distinct properties. No single measurement can fully describe tendon health.

8. Loading creates strain, and strain is a biological signal

Tendon responds to deformation created by force. Appropriate strain can stimulate adaptation, while excessive strain, excessive frequency or a rapid increase in loading can exceed repair capacity. Load programming is therefore a question of biology, not only ambition.

9. Tendons need time, not only intensity

Meta-analyses in healthy adults show that resistance training can increase tendon stiffness, modulus and, to a smaller degree, cross-sectional area. These changes emerge through repeated exposure over time, not from a few weeks of aggressive progression.

10. Muscular strength can outpace tendon adaptation

If strength rises over a short interval, the tendon is immediately exposed to greater loads even if its material properties have not changed proportionally. This is the practical meaning of the muscle-tendon mismatch: demand can rise faster than capacity.

11. AAS can accelerate gains in muscle mass and strength

Anabolic-androgenic steroids can increase protein synthesis, lean mass and training capacity. Mechanically, that can rapidly raise the forces applied to tendons. Even if the tendon were not directly altered, the larger load alone could change the injury-risk profile.

12. The mechanical mismatch hypothesis is plausible

One explanation for the association between AAS and tendon rupture is rapid muscular strength gain without equivalent connective-tissue adaptation. The hypothesis is biologically plausible and consistent with adaptation physiology, but it should not be presented as the only proven mechanism. Several pathways may act together.

13. A direct effect on the matrix is another hypothesis

Experimental and observational studies have suggested that AAS may alter collagen synthesis, organization or extracellular-matrix properties. In humans, however, it is difficult to separate those effects from training, cumulative exposure, nutrition, previous injury and other substances.

14. Human evidence has important limitations

There are no ethical randomized trials in which healthy athletes receive supraphysiological AAS doses and are then followed for tendon rupture. The literature therefore relies on cohorts, case series, imaging studies and experimental models.

15. A 2015 cohort found a strong association

In a study of 142 experienced male bodybuilders, 22% of AAS users reported at least one lifetime tendon rupture compared with 6% of non-users. The estimated hazard ratio for a first rupture was 9.0, with a wide confidence interval: a strong association, but not a mechanistic proof.

16. Upper-body tendon ruptures stood out

In the same cohort, upper-body tendon ruptures occurred exclusively in the AAS group. This pattern matters in strength sports, where the pectoralis, biceps and triceps experience very high tension during pressing, pulling and stabilization.

17. Association is not the same as proof of causation

AAS users may lift heavier loads, train more frequently, have longer training histories and use multiple substances. All of these factors can contribute to injury. Observational studies cannot perfectly separate pharmacological effects from behavioral and mechanical effects.

18. The pectoralis major tendon is a classic risk site

Pectoralis major rupture often occurs during heavy pressing, especially when the arm is extended and abducted under load. The AAS literature contains many reports involving this injury, but the final mechanism combines loading, position, tissue history and exposure.

19. The distal biceps experiences very high tension

The distal biceps tendon can be loaded severely when the elbow is forced toward extension while the biceps attempts to maintain flexion and supination. Pulling movements, unstable objects and unexpected changes in grip can create load spikes that are difficult to predict.

20. The triceps tendon can fail during explosive extension

Triceps tendon rupture is less common than some other tendon injuries, but it can occur during violent elbow extension or heavy pressing. In overhead events, log press or large-object handling, a positional error can turn a tolerable load into a sudden tension peak.

21. The patellar tendon and quadriceps tendon should be considered separately

Quadriceps tendon rupture and patellar tendon rupture are different injuries even though both affect the knee extensor mechanism. Heavy squatting, sudden changes of direction, jumping and eccentric loading can place substantial stress on this system.

22. The Achilles tendon is exposed to enormous forces

The Achilles tendon can experience forces several times bodyweight during running and jumping. In a very large athlete, acceleration, sprinting, yoke carries or rapid changes of direction increase absolute demand. Body mass and speed matter together, not separately.

23. The evidence is less clear for ligaments

Ligaments are often included in discussions of connective tissue, but human evidence specifically linking AAS to ligament injury is much thinner than the tendon literature. It is reasonable to discuss a possible biological concern without pretending that the association is equally well established.

24. Previous injury changes the risk profile

A tendon with previous injury, scar tissue, tendinopathy or surgery does not start from the same baseline as a healthy tendon. Pharmacology, training and age are layered on top of that history. An old injury can become the weak link when strength rises rapidly.

25. High volume can matter as much as high intensity

One heavy set does not describe total load. Dozens of heavy repetitions, multiple weekly sessions and frequent competitions increase the number of mechanical cycles. Tendon tissue must repair between exposures, and the recovery window can become too small.

26. Progressing too quickly shifts the capacity-demand balance

If an athlete simultaneously increases load, volume, frequency and the number of events trained, mechanical demand rises along several dimensions. When muscle strength is also accelerated pharmacologically, the gap between tissue capacity and real-world demand can widen.

27. Eccentric loading can generate high tension

Eccentric contractions can generate large forces and are useful for adaptation and rehabilitation when programmed well. But an uncontrolled eccentric under very high load can create tension peaks beyond what the tendon tolerates. Context determines whether eccentric work is stimulus or hazard.

28. Ballistic movement adds speed to the equation

Force is not the only factor. The rate at which force is applied also affects mechanical stress. A rapid movement, a lost grip or a sudden change in trajectory can increase local demand faster than the neuromuscular system can redistribute it.

29. Strongman combines heavy loading with unpredictability

Barbells and machines are relatively stable. Stones, sandbags, yokes, farmers implements, axles and asymmetric objects are not. Tendon loading can vary from step to step or repetition to repetition, and that variability can turn a small vulnerability into an injury.

30. Grip and large objects can transmit unexpected stress

In strongman events the hand may remain fixed while the body or implement moves. This can create rotation and tension around the elbow, shoulder and tendon insertions. When the load is near maximal, the margin for technical correction becomes very small.

31. Warming up does not make a tendon immune

A warm-up raises tissue temperature, prepares the nervous system and allows load to rise gradually. It is useful, but it cannot erase tendinopathy, structural injury or poorly managed progression. A vulnerable tendon remains vulnerable even if it feels better after a few sets.

32. Pain is a signal, not a precise map of tissue damage

Pain intensity does not perfectly match structural damage. Some tendinopathies are painful without major tearing, while some acute ruptures occur with little warning. Clinical assessment should combine history, examination and imaging when indicated.

33. Tendinopathy and rupture are different processes

Tendinopathy involves tendon-related pain and dysfunction, often accompanied by changes in matrix structure and load response. Rupture is a partial or complete structural failure. A painful tendon is not automatically close to rupture, and rupture does not always require a long history of pain.

34. Warning symptoms may be absent

In the classic AAS cohort, only some ruptures were preceded by nonspecific local symptoms. The absence of pain therefore does not guarantee perfect tendon integrity. Monitoring should also consider changes in function, strength, control and load tolerance.

35. Ultrasound and MRI answer different questions

Ultrasound can assess a tendon dynamically and can be useful for thickness, structure and some tears in experienced hands. MRI provides a broader view of tissues and is often used when complex injury is suspected. Neither should be interpreted without clinical context.

36. Collagen synthesis rises after loading

Tendons respond to exercise with changes in collagen synthesis and matrix turnover. That response is one reason progressive loading can be therapeutic and adaptive. But increased synthesis does not mean the tissue becomes mechanically stronger immediately.

37. Sufficient tendon strain can stimulate adaptation

Modern meta-analyses show that resistance training, particularly when it creates sufficient tendon strain, can increase stiffness and modulus. The practical message is that connective tissue needs meaningful loading, but that loading should be dosed, repeated and sustained over time.

38. Recovery is part of the training stimulus

Adaptation does not occur during the heavy set itself but while the body repairs and remodels tissue afterward. If heavy exposures overlap without adequate recovery, accumulated fatigue can exceed remodeling capacity. More training does not automatically mean more adaptation.

39. Age changes tissue properties

Collagen turnover, mechanical properties and recovery capacity change with age. A program tolerated at 20 may not be equivalent at 35 or 45, especially after tens of thousands of heavy repetitions have accumulated across a training career.

40. Sleep and nutrition influence repair

Connective tissue needs energy, amino acids, micronutrients and an appropriate hormonal environment for remodeling. Poor sleep and chaotic nutrition do not by themselves cause rupture, but they can reduce recovery quality in a system already exposed to large and frequent loads.

41. Energy availability matters for connective tissue too

Severe energy deficits can disrupt repair processes and reduce the resources available for adaptation. During aggressive weight loss or frequent competition, risk is not created only by heavy loading but also by asking the body to repair tissue with limited resources.

42. Collagen supplements are not armor

Recent studies suggest that some collagen or gelatin protocols combined with resistance training may favorably influence certain tendon measures. The effects are variable, studies remain relatively small, and supplementation cannot compensate for poorly managed load progression.

43. GH and IGF-1 can stimulate collagen synthesis

In human studies, growth hormone administration increased collagen synthesis in tendon and muscle without producing the same rise in myofibrillar protein synthesis. This shows that the GH-IGF-1 axis affects extracellular matrix biology, but it does not prove that pharmacological use prevents tendon rupture.

44. More collagen synthesis does not automatically mean better tissue

Tendon quality depends on fiber organization, cross-linking, geometry, remodeling and integration with bone and muscle. A short-term increase in a synthesis marker does not guarantee a mature structure that is resistant to maximal loading.

45. GH does not make tendons invulnerable

The idea that growth hormone simply “heals tendons” overstates the evidence. Some effects on collagen synthesis are real, but complex injuries depend on mechanics, vascularity, time, tissue type and severity. There is no pharmacological shortcut around the biology of healing.

46. Stiffness has benefits and trade-offs

A sufficiently stiff tendon can transmit force efficiently and support performance. A very compliant tendon may lose efficiency, but “as stiff as possible” is not a useful goal either. The muscle-tendon system needs properties appropriate to the task and movement, not one mechanical maximum.

47. Cumulative exposure matters

Biological risk is better understood across years of training, repeated overload episodes and cumulative exposure than within a single week. A structure may tolerate stress for a long time and then fail when fatigue, high load and pre-existing vulnerability converge.

48. Stopping AAS does not instantly reset the system

After cessation, muscular strength, body mass, hormones and training volume can change at different rates. Connective tissue does not instantly return to a simple “normal” state. Previous exposure and injury history remain relevant.

49. Previous injuries are an important predictor

A surgically repaired tendon, a tendon with chronic tendinopathy or a painful insertion requires individualized progression. Returning to maximal loads simply because pain has decreased can exceed the real mechanical capacity of the structure.

50. Rehabilitation means progressive loading

Tendons generally respond poorly both to complete abandonment of loading and to a sudden return to maximal work. Modern rehabilitation typically uses controlled load progression matched to the tendon, function and injury stage, under medical or physiotherapy guidance when appropriate.

51. Isometrics and slow resistance can have a role

Isometric exercises and heavy slow resistance are commonly used in the management of some tendinopathies. They are not universal solutions and are not appropriate for every tear or insertional problem, but they illustrate that tendon treatment still relies on intelligent force dosing.

52. Load management is prevention, not weakness

Temporarily reducing volume, changing an event or avoiding a painful angle does not mean athletic regression. Sometimes it is precisely the intervention that allows tissue capacity to catch up with demand before a manageable problem becomes structural.

53. Return to sport should be criterion-based

Time since injury is only one reference point. Strength, load tolerance, symmetry, movement control and the actual demands of the event must be considered. In strongman, tolerating a standard barbell does not automatically prove readiness for stones, axle, yoke or farmers carries.

54. Complete ruptures require prompt assessment

A complete tendon rupture can cause a pop, sudden loss of function, deformity, bruising or inability to continue normal movement. Prompt medical evaluation is appropriate because some injuries have preferred windows for surgical repair.

55. Surgery does not end the story

Surgical repair restores continuity, but months of remodeling and neuromuscular recovery follow. Returning too quickly to extreme loading can compromise the result. For a strength athlete, the goal is not merely healing but regaining tolerance for sport-specific loading.

56. Prevention in pharmacology-exposed athletes starts with realism

If strength rises quickly, external progression should respect the fact that tendons do not receive an instant upgrade. Large jumps in volume and intensity, very frequent competition and persistent disregard of pain increase pressure on a system that adapts on its own timeline.

57. Acute red flags are not negotiable

A pop, sudden weakness, loss of function, deformity or extensive bruising after a heavy movement justifies stopping and obtaining assessment. Trying another repetition to “test it” can turn a partial injury into a more severe one.

58. Blood tests do not measure tendon strength

Testosterone, IGF-1, inflammatory markers or enzymes cannot tell how close a tendon is to rupture. Connective-tissue health is evaluated through history, function, clinical examination and imaging when needed, not through a single laboratory marker.

59. The engine and chassis must be built together

An athlete can have muscles capable of producing a force that the tendons, insertions and joints are not yet ready to transmit repeatedly. Intelligent programming targets adaptation of the entire chain, not only a larger number on the bar.

60. Conclusion: strength is produced by muscle, but paid for by the entire chain

AAS can accelerate strength gains, and human data associate their use with a greater risk of tendon rupture, particularly in the upper body. The mechanisms are probably mixed: greater loads, slower connective-tissue adaptation and possible direct matrix effects. Tendons and ligaments must be treated as real biological constraints on performance.

The first key point is that muscle, tendon and ligament do not adapt at the same rate. Rapid strength gains can increase mechanical demand faster than connective tissue remodels.

The second point is that the association between AAS and tendon rupture is supported by observational human evidence, but the exact mechanism remains mixed and cannot be fully separated from training, loading, age and other exposures.

The third point is that evidence is stronger for tendons than for ligaments. The literature does not justify treating all connective tissues as if they respond identically to AAS.

The fourth point is that connective tissue responds to loading. Well-dosed progression, recovery and sufficiently long exposure can improve tendon mechanical properties, while sudden load jumps increase the gap between demand and capacity.

Finally, performance depends not only on how much force muscle can produce, but also on how much force tendons, insertions, ligaments and joints can safely transmit and control.

Sources and recommended reading

1. Kanayama G, DeLuca J, Meehan WP III, Hudson JI, Isaacs S, Baggish A, Weiner R, Micheli L, Pope HG Jr. Ruptured Tendons in Anabolic-Androgenic Steroid Users: A Cross-Sectional Cohort Study. American Journal of Sports Medicine. 2015.

2. Pope HG Jr, Wood RI, Rogol A, Nyberg F, Bowers L, Bhasin S. Adverse Health Consequences of Performance-Enhancing Drugs: An Endocrine Society Scientific Statement. Endocrine Reviews.

3. Żywiec W et al. Impact of Anabolic Steroids on Tendons: A Narrative Review. Cureus. 2025.

4. Lazarczuk SL, Maniar N, Opar DA, Duhig SJ, Shield A, Barrett RS, Bourne MN. Mechanical, Material and Morphological Adaptations of Healthy Lower Limb Tendons to Mechanical Loading: A Systematic Review and Meta-Analysis. Sports Medicine. 2022.

5. Bohm S, Mersmann F, Arampatzis A. Human Tendon Adaptation in Response to Mechanical Loading: A Systematic Review and Meta-Analysis of Exercise Intervention Studies on Healthy Adults. Sports Medicine - Open.

6. Doessing S et al. Growth Hormone Stimulates the Collagen Synthesis in Human Tendon and Skeletal Muscle Without Affecting Myofibrillar Protein Synthesis. Journal of Physiology. 2010.

7. Kjaer M. Role of Extracellular Matrix in Adaptation of Tendon and Skeletal Muscle to Mechanical Loading. Physiological Reviews.

8. Magnusson SP, Langberg H, Kjaer M. The Pathogenesis of Tendinopathy: Balancing the Response to Loading. Nature Reviews Rheumatology.

9. Sports-medicine literature on tendinopathy, pectoralis major rupture, distal biceps rupture, triceps rupture and extensor-mechanism injuries in strength athletes.

10. Rehabilitation literature on progressive loading, tendon mechanical properties, return to sport and functional criteria after tendon injury.

Editorial note: this article is educational and does not provide instructions for AAS or other PED use. Persistent pain, sudden loss of function, deformity, extensive bruising or suspected tendon rupture requires assessment by a qualified medical professional.