A marathon seems like it's all about endurance. But here's something that surprises many runners: two people with identical VO2max and lactate threshold can run very different marathon times. The difference is often running economy, which is how much energy it costs to run at a given pace.
Running economy is largely a neuromuscular quality. It depends on how efficiently your brain communicates with your muscles, how well your tendons store and release energy, and how coordinated your movement is. These things are trained through short, fast efforts, not through more easy miles.
What "Neuromuscular" Means
Every time you take a stride, your brain sends electrical signals through your spinal cord to your muscles, telling specific fibres to contract in a precise sequence with precise timing. This is your neuromuscular system: the wiring between your brain and your body.
The quality of this wiring determines:
- How many muscle fibres activate per stride. More recruitment means more force without more perceived effort.
- How fast the signal travels. Quicker signalling means shorter ground contact time and more responsive adjustments.
- How well muscles coordinate. Good coordination means less wasted energy. Opposing muscles aren't fighting each other, and force is directed into forward motion.
You can have a massive aerobic engine and a high lactate threshold, but if your neuromuscular system is inefficient, you're burning extra fuel with every step. Over 42 kilometres, that adds up.
What Changes Inside Your Body
Motor Unit Recruitment
A motor unit is a nerve cell plus all the muscle fibres it controls. When you run at easy pace, your body only activates a fraction of available motor units. It's conserving resources. Short, fast efforts force recruitment of motor units that normally sit idle, including fast-twitch fibres.
With repeated exposure, two things happen: your body learns to recruit these units more readily, and the units themselves become more fatigue-resistant. This means more muscle mass contributing to each stride at all paces, including marathon pace.
Rate Coding
Rate coding is how quickly nerve signals fire. Faster firing means faster muscle contraction, which means quicker ground contact and more elastic energy return. Training at high speeds increases the rate at which your nervous system can send signals, even though you'll never use maximum firing rate during a marathon. The benefit transfers downstream: slightly faster, crisper muscle activation at every pace.
Tendon Stiffness and Elastic Recoil
Your tendons aren't just passive connectors. They're springs. When your foot hits the ground, your Achilles tendon and the tendons around your knee absorb energy and release it during push-off. Stiffer tendons store and return energy more efficiently.
Short, high-force efforts (like hill sprints) load tendons at levels that stimulate this stiffness adaptation. It's one of the few ways to directly improve the elasticity of the running stride. The result is more "free" energy per step, speed that costs you nothing metabolically.
Intermuscular Coordination
Running involves dozens of muscles working in sequence. Efficient running means the right muscles fire at the right time and the wrong muscles stay quiet. Poor coordination looks like excess tension in the shoulders, unnecessary bounce, or a choppy stride.
Fast running forces your body to coordinate more precisely because there's less time per stride to get it right. This improved timing carries over to slower paces, where the movements become smoother and less effortful.
Running Economy: Why This Matters for Marathons
Running economy is the oxygen cost of running at a given speed. A more economical runner uses less oxygen, and therefore less energy, at the same pace. Among trained runners with similar VO2max values, running economy is often the best predictor of marathon performance.
Improvements in running economy come from the adaptations above: better recruitment, faster signalling, stiffer tendons, cleaner coordination. They can't be built through slow running alone. Easy miles develop the aerobic engine, but they don't meaningfully improve the efficiency with which that engine translates energy into speed.
This is why even high-mileage runners benefit from neuromuscular work. It's a different signal to the body. Not "produce more energy" but "waste less of the energy you're already producing."
How to Train It
What Makes CNS Training Different
Unlike aerobic, threshold, or VO2max training, CNS work is defined by very short efforts with full recovery. The efforts are fast, near maximal, but the total volume is tiny. A session might include only 60-120 seconds of actual fast running across all repetitions combined.
This is by design. The stimulus is neural, not metabolic. You're training the wiring, not the engine. Fatigue actively undermines the goal because a tired nervous system sends slower, sloppier signals. So the efforts are short enough that metabolic fatigue never accumulates, and the recovery is long enough that each rep is crisp.
Intensity
- Heart rate: not useful as a guide. The efforts are too short for heart rate to respond accurately.
- Feel: fast, smooth, and controlled. Not straining or forcing.
- RPE: 8-9 out of 10 for the effort itself, but brief enough that overall session fatigue is low.
- Pace: near maximal but not all-out. The goal is speed with good form, not speed at any cost.
Volume
Low. Always low.
- Strides (a modifier, not a standalone workout): 4-8 reps of 15-20 seconds, appended to easy runs
- Hill sprints: 4-10 reps of 8-15 seconds, full walk-back recovery
- Flat sprints: 4-8 reps of 10-20 seconds, 60-90 seconds full recovery
The total hard running in a CNS session is 1-3 minutes. If you feel significantly tired afterwards, you've done too much or gone too hard.
When in the Training Cycle
One of the unique features of neuromuscular training is that it belongs in every phase. The fatigue cost is so low that it doesn't compete with other training priorities:
- Base phase: Strides after easy runs 2-3 times per week. Hill sprints 1-2 times per week after easy runs. This maintains speed and builds structural strength while the aerobic system develops.
- Build phase: Continued alongside threshold work. Strides remain regular. Hill sprints may reduce as other intensity increases.
- Peak phase: Strides stay. They keep the nervous system sharp during the highest-stress training weeks without adding meaningful fatigue.
- Taper phase: Strides are among the last elements removed before race day. A few short accelerations 2-3 days before the race maintain neuromuscular readiness with zero fatigue cost.
How Long It Takes
Neuromuscular adaptations are fast, among the fastest in all of training.
Building: Neural adaptations (better recruitment, faster signalling) begin within 2-4 weeks. Tendon stiffness takes longer, roughly 6-8 weeks of consistent loading. The coordination improvements are progressive and ongoing.
Maintaining: Very easy to maintain. A few strides per week is enough to preserve neuromuscular gains. This is why strides persist across all training phases.
Losing: Pure neural adaptations fade within 2-3 weeks without any fast running. But because the maintenance dose is so small (strides take 3 minutes), there's rarely a reason to let them go.
The Workouts and Modifiers That Build It
Standalone workouts:
- Hill sprints are 8-15 seconds at maximum effort on a steep hill. The incline limits top speed (reducing injury risk) while generating high forces that build leg power and tendon strength. Walk back down for full recovery.
- Sprints are near-maximal flat running for 10-20 seconds. This develops pure speed and top-end neuromuscular power. Primarily for experienced runners who have built structural resilience through hill sprints first.
Modifiers (combined with other workouts):
- Strides are the most important neuromuscular tool for marathon runners. Short, controlled accelerations done after easy runs or before workouts. They're the primary way CNS adaptation gets delivered within a training week, not as a separate session, but as a 3-minute addition to runs that are already happening.
The distinction between workouts and modifiers matters for programming. Hill sprints and sprints are sessions with their own warmup and purpose. Strides are layered onto other runs to add a neuromuscular stimulus without adding a session to the schedule. This is how a training plan delivers 3-5% of its weekly volume as CNS work without needing a dedicated speed day.
The Relationship to Other Adaptations
CNS training is the complement to everything else. Aerobic training builds the engine. Threshold training raises sustainable pace. VO2max training lifts the ceiling. Neuromuscular training makes all of them more efficient.
A runner who only does easy miles develops a big engine but runs inefficiently. A runner who only does speed work is fast but can't sustain it. The combination, primarily aerobic volume with small, consistent doses of neuromuscular work, produces a runner who is both durable and economical.
For marathon training specifically, the neuromuscular contribution is small in volume (3-5% of weekly running) but disproportionate in impact. Improved running economy means less oxygen consumed per kilometre, which means more margin at race pace, which means a faster or more comfortable marathon. It's the cheapest adaptation to maintain and one of the most valuable to have.