Endurance athletes — runners, cyclists, triathletes, and rowers — are often celebrated for cardiovascular fitness and metabolic efficiency. Yet a key adaptation that rarely gets the spotlight is muscle loss: the gradual decline of muscle mass and strength that can occur when long‑duration aerobic work dominates training. As emerging research shows, neglecting hypertrophy and resistance training can blunt performance gains and undermine long‑term health.
Why Muscle Matters — Even for Endurance Athletes
Endurance training brings huge cardiovascular benefits: increased mitochondrial density, improved capillarization, and enhanced fat oxidation. These adaptations help athletes sustain effort for longer but don’t build muscle mass — and in some cases can create a muscle maintenance deficit if not balanced with strength work.
Without targeted resistance stimulus, athletes may experience reductions in type II muscle fiber size, a shift that impacts force production, power, and daily function. One controlled trial found that strength training led to significant hypertrophy (≈26% increase in type II fiber cross‑sectional area), whereas endurance or mixed training did not.
Endurance + Hypertrophy: The Case for Balance
The myth that endurance training alone will preserve muscle falls short — especially when training volume and intensity are high. While combining strength and endurance shows varied results, numerous reviews suggest that adding resistance training enhances neuromuscular function and supports muscle size without compromising endurance performance when programmed appropriately.
➡️ What’s a Balanced Exercise Program?
Resistance and hypertrophy work offer distinct benefits that extend beyond aesthetics:
Improved power and economy: Stronger muscles produce force more efficiently, improving running economy and cycling power without adding unnecessary bulk.
Metabolic health: Muscle is the primary site of glucose disposal. More lean tissue enhances insulin sensitivity and long‑term metabolic health.
Functional resilience: Greater muscle mass correlates with lower injury risk and better fatigue resistance — especially late in races and training blocks.
Muscle Protein Synthesis and Endurance Training
Endurance athletes often have high training loads that increase energy expenditure and protein turnover. Yet maximizing muscle protein synthesis (MPS) requires strength stimuli and adequate protein intake to offset catabolic effects — especially in long training seasons. Research highlights the interplay between resistance exercise, protein consumption, and recovery for muscle growth and retention.
➡️ Strength Training for Longevity: Why Muscle Is the New Vital Sign
How to Add Hypertrophy Work Without Hurting Endurance
Here’s a practical framework:
Twice Weekly Resistance Sessions
Include compound lifts (squats, deadlifts, presses, rows) and moderate‑to‑heavy loads aimed at hypertrophy (6–12 reps, progressive overload).Strategic Programming
Schedule strength sessions on low‑volume cardio days or separate them from long aerobic workouts to prevent interference and optimize recovery.Nutrition Support
Ensure adequate protein (aiming for 1.6–2.2 g/kg body weight/day) to support MPS and recovery.
➡️ How Much Protein Do You Need to Achieve Your Fitness Goal?
Recovery Focus
Prioritize sleep, hydration, and refueling after both endurance and strength sessions.
Common Misconceptions
“Hypertrophy makes endurance athletes too bulky.” Not true when programmed smartly — added muscle enhances strength without substantial weight gain if nutrition and goals are monitored.
“Endurance training provides enough stimulus.” Endurance builds cardiovascular systems — but it doesn’t substitute the neuromuscular stimulus required for muscle growth.
➡️ 10 Nutritional Supplements for Endurance Athletes
References
American College of Sports Medicine. (2022). ACSM’s guidelines for exercise testing and prescription (11th ed.). Wolters Kluwer.
Devkota, A., Gautam, M., Dhakal, U., Devkota, S., Gupta, G. K., Nepal, U., & Dhuru, A. D. (2024). The interplay between physical activity, protein consumption, and sleep quality in muscle protein synthesis. arXiv.
Devkota, A., Gautam, M., & Nepal, U. (2023). Effects of aerobic exercise on skeletal muscle adaptations: Evidence from endurance athletes. Khel Journal, 10(1), 66–82.
South, J., & East, M. (1998). Current knowledge on muscle training: Endurance and strength yield complementary effects. PubMed.
Tesch, P. A., et al. (2009). Effects of combined endurance and strength training on muscle strength and hypertrophy. PubMed.