Original episode & show notes | Raw transcript
For endurance athletes, particularly cyclists, the question of whether to incorporate heavy strength training is a long-standing debate with two main camps:
The “Off-Season Only” Camp: This traditional periodization view argues that strength training is not specific to the primary sport. Therefore, it should be confined to the off-season and base-building phases and eliminated as the competitive season approaches to maximize sport-specific fitness.
The “Year-Round Maintenance” Camp: This school of thought posits that the strength and power built in the off-season are valuable assets that will diminish if not maintained. Since cycling, even sprinting, involves relatively low force compared to maximal lifting, proponents argue for year-round lifting to preserve these gains.
Understanding the science behind how our bodies adapt to these different stimuli is key to navigating this dilemma and making the best choice for your athletic goals.
While benefits like increased bone density are crucial for athletes in low-impact sports like cycling, the most immediate and significant gains from strength training are neural.
Mind-Muscle Connection: This isn’t a vague concept; it refers to the efficiency of your nervous system. Strength training improves neural drive and motor unit recruitment. Your brain becomes better at sending strong, coordinated signals to your muscles, activating more muscle fibers simultaneously to produce greater force.
Rapid Initial Gains: When someone is new to lifting, they see dramatic increases in the weight they can lift within the first few weeks. This isn’t primarily due to muscle growth (hypertrophy), but rather the brain and nervous system learning to execute the movement more efficiently.
Maintaining Force Production: During a long race season, an athlete might experience a decline in “strength.” This is often not a loss of actual muscle mass but a detraining of the neural pathways responsible for maximal force production. The brain simply loses practice in telling the muscles to contract that hard. A small amount of in-season lifting can maintain this neural connection, which is crucial for sprinting, climbing, and responding to attacks.
The core issue with combining strength and endurance training is a phenomenon known as the interference effect.
The Hickson (1980) Study: A Landmark Experiment
This was one of the first studies to systematically investigate concurrent training (doing both strength and endurance training simultaneously).
The Setup: Participants were split into three groups for a 10-week period:
Strength Group: Lifted 5 days a week (squats, leg press, etc.).
Endurance Group: Trained 6 days a week (alternating VO2 max intervals and steady-state running/cycling).
Concurrent Group: Performed both the strength and endurance protocols.
The Results:
VO2 Max (Endurance): The Endurance group and the Concurrent group saw similar, significant increases in their VO2 max. The Strength group saw none.
1-Rep Max Squat (Strength): The Strength group’s 1RM increased by an average of 44%. The Concurrent group’s strength increased identically for the first seven weeks, but then it plateaued and began to decline.
The Conclusion: The study demonstrated that while strength training did not interfere with aerobic adaptations, intense endurance training actively interfered with the ability to continue gaining strength.
Modern science has revealed the molecular pathways that explain Hickson’s findings. Adaptation is a battle for resources within the cell, governed by competing signaling pathways.
What it is: The mammalian Target of Rapamycin (mTOR) is the master regulator of muscle protein synthesis. When mTOR is activated, it signals the cell to build new proteins and grow larger.
How it’s triggered:
Mechanical Load: Heavy resistance training is a potent activator.
Amino Acids: The presence of amino acids, particularly leucine, also stimulates mTOR.
Duration: The mTOR signal is long-lasting. In new lifters, it can remain elevated for 24-48 hours after a workout. In trained individuals, it’s closer to 18 hours.
What it is: PGC-1α is the primary driver of aerobic adaptations, most notably mitochondrial biogenesis (creating more mitochondria, the powerhouses of the cell).
How it’s triggered: By the metabolic stress of endurance exercise, including changes in cellular energy levels (AMP/ATP ratio), calcium fluctuations, and glycogen depletion.
Duration: The PGC-1α signal is powerful but brief, peaking and then returning to baseline within about 3 hours post-exercise.
The critical discovery is that the PGC-1α pathway (along with a related energy-sensing protein, AMPK) actively inhibits the mTOR pathway.
When you perform endurance exercise, you trigger a strong PGC-1α signal. This signal essentially tells the cell, “Prioritize aerobic adaptation and energy efficiency now; shut down the resource-intensive process of building new muscle.” Because the aerobic signal takes evolutionary precedence, it can override the muscle-building signal.
Understanding these pathways allows you to structure your training to achieve your desired outcome.
1. Training Order and Timing Matter Because the PGC-1α signal is short-lived (3 hours) while the mTOR signal is long-lived (18+ hours), you can manipulate the timing of your workouts.
To Maximize Strength: Lift first. This allows the mTOR signal to be activated without immediate interference. If you wait several hours before your endurance session, you can get the benefit of both adaptations.
To Blunt Muscle Growth: If your goal is purely neural maintenance without gaining mass, doing a short, moderate-intensity aerobic session (e.g., 15-20 minutes of spinning) immediately after lifting can be effective. This activates PGC-1α and shuts down the mTOR signal, preventing significant hypertrophy.
2. Mind Your Fiber Types Muscle fibers are plastic and adapt to the stimulus you provide.
Strength Training: Promotes Type II (fast-twitch, powerful) fibers.
Endurance Training: Promotes Type I (slow-twitch, efficient, fatigue-resistant) fibers.
Concurrent Training: Can cause both fiber types to grow, but it may prevent a significant shift toward the highly efficient Type I profile that is advantageous for pure endurance events. Heavy year-round lifting may effectively “lock” your fiber type profile in place.
3. Use Nutrition as a Tool You can stimulate the mTOR pathway without lifting.
Leucine: This branched-chain amino acid (BCAA) is a direct, albeit modest, stimulator of mTOR. Consuming leucine-rich foods (whey protein, dairy, meat) can help signal muscle maintenance.
Protein Distribution: To maximize muscle protein synthesis, it’s more effective to consume moderate servings of protein (e.g., 20-25 grams) periodically throughout the day rather than one massive serving. This provides a steady supply of amino acids for your muscles.
4. Periodize Your Goals
Off-Season/Base: This is the ideal time for a dedicated strength block. Endurance volume is lower, minimizing the interference effect and allowing for maximal gains in muscle mass and strength.
In-Season/Build: The focus should shift. Lifting can be reduced to once a week, focusing on maintaining the neural ability to produce high force. The goal is no longer to build, but to preserve. Removing the heavy lifting stimulus entirely often leads to a breakthrough in aerobic performance, as the body is freed from the competing signal and recovery demands.