Original episode & show notes | Raw transcript
The podcast begins by addressing a fundamental question for many endurance athletes: Is strength training beneficial? While the intuitive answer might be “yes, getting stronger is good,” the scientific literature is often conflicting and confusing. The host points out several recurring issues with studies on this topic:
Untrained Subjects: Many studies use participants who are untrained or only recreationally active. In these individuals, any form of training will likely lead to improvements across the board (a phenomenon often called “newbie gains”). This makes it difficult to isolate the specific effects of strength training on a well-trained endurance system.
Small Sample Sizes: Many studies have too few participants to draw statistically significant conclusions.
Lack of Specificity: The strength training protocols used in studies often don’t reflect what a cyclist or endurance athlete would or should do. They are frequently borrowed from bodybuilding, powerlifting, or general team sports, which have different physiological goals than endurance cycling.
To get around these issues, the podcast focuses on a specific, well-designed study that provides a clearer picture.
Participants: Elite under-23 cyclists, ensuring a highly trained population.
The Groups:
Group 1 (Endurance Only): Performed 10-18 hours of endurance riding per week.
Group 2 (Strength + Endurance): Did the same endurance riding but also added heavy weightlifting 2-3 times per week.
The Protocol: The strength training was heavy, focusing on 5-6 repetition maximums (rep maxes). This is a classic approach to building maximal strength.
The Results: This is where it gets interesting.
No Change in Aerobic Markers: After 16 weeks, neither group saw a change in their VO2 max or their Functional Threshold Power (FTP).
Improved 45-Minute Power: The strength-training group saw an 8% increase in their 45-minute time trial power (from ~315 watts to ~340 watts). The endurance-only group saw no such improvement.
This outcome presents a puzzle: How did the cyclists get significantly better in a 45-minute effort without any improvement in their fundamental aerobic metrics? The podcast then systematically debunks the common explanations.
This is directly contradicted by the data. Since VO2 max (the maximum rate of oxygen consumption) and FTP (a marker of sustainable aerobic power) did not increase, the improvement did not come from a better aerobic engine. In elite athletes, VO2 max is primarily limited by central factors (heart and lungs), which heavy lifting does not train effectively.
This is also incorrect. The study found that the cyclists’ body weight and muscle size remained the same. The podcast explains this is likely due to the “interference effect,” where the signaling pathways for aerobic adaptation (like those stimulated by long-duration cycling) can inhibit the pathways for muscle growth (hypertrophy). For many cyclists who want to avoid gaining mass, this is actually a desirable outcome.
This is one of the most common arguments, and it sounds logical, but the math doesn’t support it. The theory is that if your one-rep max squat goes up, the force required for each pedal stroke at FTP is now a lower percentage of your new, higher maximum, making it less costly.
The podcast breaks it down:
Pedaling at an FTP of ~300 watts requires about 170 Newtons (N) of average force on the pedals.
An average road cyclist can produce a maximal force of about 1,000 N.
So, pedaling at FTP requires about 17% of their maximal force.
The strength-training group increased their maximal voluntary contraction by 12-20%. Let’s say their max force went from 1,000 N to 1,150 N.
Now, pedaling at FTP requires about 14.8% of their new maximal force.
This is a negligible change. A drop of ~2% in relative intensity cannot explain an 8% increase in power output. The conclusion is that sustained endurance performance is not limited by maximal force production; it’s limited by metabolic factors—specifically, the sustained demand for ATP (the body’s energy currency).
Having debunked the common theories, the podcast presents the true explanation, which lies in the way our nervous system controls our muscles.
A muscle is not just one big unit. It’s composed of thousands of individual muscle fibers. The brain controls these fibers via motor neurons. A single motor neuron and all the muscle fibers it connects to is called a motor unit.
Small Motor Units: Connect to a small number of muscle fibers (10-180). These fibers are typically Type I (slow-twitch)—highly efficient, fatigue-resistant, and excellent at using oxygen.
Large Motor Units: Connect to a large number of muscle fibers (300-800). These fibers are typically Type II (fast-twitch)—less efficient, highly powerful, but fatigue quickly.
This is the crucial concept. Your body recruits motor units in a specific order to meet force demands: from smallest to largest.
When you start pedaling easily, your brain sends a weak signal, activating only the small, efficient, slow-twitch motor units. As you need to produce more force (e.g., climbing a hill or increasing your pace), your brain sends a progressively stronger signal. This stronger signal surpasses the activation threshold for larger and larger motor units, recruiting the more powerful, fast-twitch fibers. Critically, the smaller units remain active; the larger ones are added on top.
Neural drive is the strength of the signal your brain can send to your muscles. Most people cannot voluntarily recruit 100% of their motor units. Their brain simply cannot generate a strong enough signal. This can be a protective mechanism to prevent injury. However, neural drive can be trained.
This is exactly what the heavy lifting did. The 5-6 rep max lifts forced the cyclists’ central nervous systems to generate extremely powerful signals to move the heavy weight. This trained their neural drive.
Here is the final synthesis:
Trained Neural Drive: The strength-training group developed a greater neural drive, meaning they could send a stronger signal to their muscles for a longer period.
Access to More Motor Units: This enhanced neural drive gave them access to larger motor units that the endurance-only group couldn’t recruit, especially under fatiguing conditions.
Access to More Fuel: Each muscle fiber contains its own glycogen (fuel) stores. By recruiting these previously inaccessible motor units, the cyclists effectively unlocked new, fresh fuel tanks deep into their 45-minute effort.
Increased Fatigue Resistance: As the smaller, primary motor units began to fatigue and run low on glycogen during the time trial, the strength-trained cyclists could “dig deeper” and recruit these larger, fresh units to maintain power. The endurance-only group, with their less-trained neural drive, hit a wall sooner because they couldn’t access these reserves.
The 45-minute time trial exists in a unique physiological zone—above FTP but below VO2 max—where fatigue resistance is heavily influenced by your ability to continue recruiting muscle fibers as others tire. The strength training specifically improved this “neural fatigue resistance,” leading to the 8% power increase.
You only train the muscle fibers you recruit. If you never perform efforts that require high force, you will never train the large motor units or the neural pathways that control them.
Strength training is a potent tool for improving neural drive, which can be a limiter in performance, even for highly trained endurance athletes.
The effect is highly individual. Athletes with a history of strength training may already have a well-developed neural drive and see less benefit.
This does not mean all cyclists must lift heavy year-round. There are on-the-bike methods to train neural drive (e.g., high-torque, low-cadence intervals or maximal sprints), though the podcast host considers these a “trade secret.” The key is to understand the principle so you can apply it intelligently to your own training.