Aging, Strength, and Tendons: What Really Happens, and How to Train for It

The biggest misconception in strength training is that aging is the primary reason athletes lose muscle, strength, and tendon capacity. The narrative is pessimistic. You hit 30, things start falling apart, and by 40 or 50 the decline is supposedly unavoidable. The good news is that research shows something completely different.

Muscle tissue remains highly trainable into the seventh, eighth, and even ninth decade of life. Tendons also remain adaptable, but the inputs required to maintain them become more precise with age. The problem isn’t aging, but disuse, poor programming, inadequate nutrition, and abrupt spikes in load.

This article breaks down what actually happens to muscles and tendons in aging athletes, and what the science tells us about how to train for long-term performance, resilience, and tissue health.

1. Muscle Loss Is Mostly Behavioral, Not Biological

Population studies show a slow, linear decline in muscle mass beginning around age 20. Many people assume this represents a biological aging clock ticking down. But when we look at the determinants of muscle loss, two factors dominate:

  • Physical inactivity

  • Insufficient protein and calorie intake

A major review by Kim et al. stated it bluntly:

“The primary causes of sarcopenia include a sedentary lifestyle and malnutrition.”

When you compare sedentary adults to master athletes, the gap is enormous. Lifelong exercisers show dramatically less muscle loss and often maintain high-level function well into older adulthood.

Even in controlled training environments, older adults produce similar hypertrophy to younger adults:

  • Adults in their 60s and 70s gain as much lean mass as people in their 20s during supervised strength training.

  • In several studies, 70-year-olds gained the same muscle volume and strength as people 50 years younger.

  • People in their 80s and 90s still demonstrate significant strength increases, 174% in one study over eight weeks.

A large meta-analysis found that age only explains 10% of the variation in hypertrophy after 60. The other 90% comes from training load, volume, nutrition, recovery, and lifestyle. The bottom line is that age changes the inputs required, not the potential to adapt.

2. Tendons Do Age Biologically, But They’re Still Trainable

The muscle’s story is straightforward, it stays robust with training. Tendons are more nuanced. They undergo real biological and mechanical changes with age:

Structural Changes

  • Increased collagen cross-linking (AGEs)

  • Reduced proteoglycans and water content

  • Disorganized collagen alignment

  • Reduced stem cell activity and increased cellular senescence

These changes affect the material properties of the tendon. Essentially how the tendon behaves under load.

Mechanical Changes

Sedentary aging tends to produce:

  • Reduced stiffness

  • Reduced elastic modulus

  • Increased strain for the same load

  • Poorer energy storage and return

  • Slower force transmission

Functionally, these changes can decrease power output, impair stretch–shortening efficiency, and increase injury risk.

Active Master Athletes Look Completely Different

In contrast, people who continue to train, a lot, age very differently:

  • Tendon stiffness is often maintained or increased

  • Tendon cross-sectional area can increase with heavy loading

  • Muscle–tendon behavior remains smooth and coordinated

  • Heavy strength training increases tendon stiffness even in 60–75-year-olds

Tendon adaptation slows with age, but it does not stop. And well-planned strength training mitigates nearly every degenerative change we worry about.

3. Why Tendon Injury Risk Increases With Age

Age alone isn’t the issue, load management is. Injury risk increases when:

  1. Tendons decondition from years of underloading

  2. Strength gains outpace tendon adaptation

  3. Abrupt volume or intensity spikes exceed tendon tolerance

  4. ECM quality declines from inactivity

  5. Recovery windows aren't respected

Most tendon injuries in aging athletes are predictable. A sudden return to high-intensity training after years of inconsistent load. The tendon simply isn’t conditioned to buffer those forces.

4. How to Train Muscle and Tendon Health as You Age

The solution is not backing off. The solution is precision.

1. Training Volume

  • 10–15 hard sets per muscle group per week

  • 12–18 sets/week for legs and back

  • 8–12 sets/week for forearms and smaller groups

Climbers specifically need:

  • Finger flexors: 8–12 high-tension sets/week

  • Shoulder stabilizers: 8–12 sets

  • Forearm/biceps: 6–10 sets

2. Training Frequency

  • Each muscle group 2–3×/week

  • Tendons respond better to frequent moderate loading than infrequent maximal loading

  • Climbers should train fingers 3–4×/week (at mixed intensities)

3. Intensity

  • Strength maintenance: ≥70% 1RM

  • Strength gains: 80–90% 1RM

  • Heavy isometrics: 85–95% MVIC for 4–6 seconds

  • Hypertrophy across 30–85% 1RM as long as sets reach 0–2 RIR

Finger training:

  • Density hangs: 50–70% MVIC

  • Recruitment pulls/lifts: 85–95%

  • Velocity hangspower: lower load, higher intent

4. Power Training

Power is the first capacity to decline with age. It needs direct training.

  • 2×/week

  • 3–5 sets of 3–5 reps

  • 30–50% 1RM or bodyweight

  • Maximal intent/speed

Climbers:

  • Velocity pulls

  • Contact strength drills

  • Power-style bouldering

5. Protein and Nutrition

Older adults need:

  • 1.6–2.2 g/kg/day

  • 0.4–0.6 g/kg per meal

  • ~40 g post-training

6. Creatine

One of the highest-value supplements in aging athletes.

  • 3–5 g/day

  • Improves strength, lean mass, cognitive function

7. Load Progression for Tendon Health

  • Increase weekly load 5–10%

  • Allow 2–4 weeks for tendons to adapt to new intensities

  • Do not stack high-strain days

  • Use long-duration isometrics for reactivity

  • Monitor morning stiffness and crimp sensitivity

Final Thoughts

Aging doesn’t remove your ability to build strength or tissue capacity. What changes is your margin for error and the precision required in training. Muscle remains incredibly plastic well into older adulthood. Tendons require more thoughtful progression, but they respond exceptionally well to consistent loading.

The evidence is overwhelmingly clear:

Decline is not inevitable. Disuse is.

Train hard, train smart, eat enough protein, and your musculoskeletal system will remain adaptable for decades longer than most people assume.

References

  • Kim TN, Choi KM. Sarcopenia: definition, epidemiology, and pathophysiology. J Bone Metab. 2013.

  • Melton LJ et al. Epidemiology of sarcopenia. Bone. 2015.

  • Roth SM et al. Muscle size responses to strength training in young and older adults. J Appl Physiol. 2001.

  • Ivey FM et al. Muscle hypertrophy with resistance training in the elderly. J Appl Physiol. 2000.

  • Mayhew DL et al. Age impact on muscle hypertrophy and strength. Exp Gerontol. 2009.

  • Loenneke JP et al. Age and hypertrophy responsiveness. Eur Rev Aging Phys Act. 2017.

  • Kittilsen H et al. Age effects on strength gains. Eur J Appl Physiol. 2021.

  • Marcuza-Nassr GN et al. Strength training from 65 to 85+. J Gerontol A. 2023.

  • Straight CR et al. Meta-analysis on age and hypertrophy. Sports Med. 2020.

  • Wroblewski AP et al. Muscle health in master athletes. Phys Sportsmed. 2015.

  • Magnusson SP et al. Tendon aging and adaptation. Scand J Med Sci Sports.

  • Narici MV, Maffulli N. Tendon structure and function with aging. J Appl Physiol.

  • Couppe C et al. Human tendon adaptation to mechanical loading. J Appl Physiol.

  • Reeves ND et al. Tendon adaptation in older adults. J Physiol.

  • Arya S, Kulig K. Tendinopathy and tendon mechanics. J Orthop Sports Phys Ther.

Tyler Nelson