Where does Protein Fit into Performance Nutrition?

Most people think performance nutrition is concerned with the time between when they clip into their pedals or lace up their trainers and ends when they stop the activity and upload it to Strava. In reality, that's often the easiest part. 

For most endurance athletes, fuelling during exercise is relatively straightforward. Modern sports nutrition has given us clear guidelines around carbohydrate intake, hydration and energy replacement. While there is certainly an art to getting this right, the principles themselves are relatively well established. However, performance nutrition isn't simply about the ride, run or race itself. It's about everything that happens between finishing today's session and starting the next one. What you eat in the hours after training influences how effectively you recover, how well your body adapts to the work you've just completed and ultimately how prepared you are to perform again tomorrow, next week and next month. 

This is where protein becomes one of the most important nutrients in endurance sport. Unlike carbohydrates, which primarily fuel performance, protein supports the adaptations that occur because of training. The training session itself is only the stimulus. The improvements occur afterwards, and protein is one of the key building blocks that allows those improvements to happen. 

Following exercise, the body enters a period of repair. Damaged proteins within muscle tissue are broken down and replaced, new proteins are synthesised and the structures responsible for force production become stronger and more resilient. This process is known as Muscle Protein Synthesis (MPS), and it is heavily dependent on the availability of dietary protein. Without sufficient protein, the repair process can still occur, but it becomes less efficient. Recovery may take longer, adaptation may be reduced and the athlete can find themselves carrying greater levels of fatigue from one training session to the next. 

This is one of the reasons protein requirements for endurance athletes are generally higher than those recommended for the general population. This surprises many endurance athletes because protein has traditionally been associated with strength athletes. However, endurance training places substantial demands on muscle tissue too. The difference is simply that the adaptations being sought are different. While a bodybuilder may be trying to maximise muscle size, a cyclist is trying to maximise recovery, preserve lean mass, improve training adaptation and remain resilient enough to complete tomorrow's session at a high level. 

The benefits extend far beyond simply repairing muscle fibres. Modern research suggests protein also plays important roles in mitochondrial adaptation, immune function, enzyme production and glycogen restoration following exercise (Witard et al., 2025). In other words, protein isn't simply helping repair the muscles; it is helping improve the muscles performance as well. This becomes increasingly important during periods of heavy training load, where every session creates a small amount of stress that must be absorbed, repaired and adapted to. When recovery is insufficient, fatigue accumulates faster than fitness; The legs feel heavy, recovery takes longer than expected, consecutive training sessions become progressively harder, and performance begins to plateau despite consistent effort. 

So, if protein is so important for recovery and adaptation, the obvious question becomes whether consuming more protein improves performance. At first glance, the answer appears less straightforward than with carbohydrates. If you consume a gel during a ride, you can often feel the benefit within minutes. Protein doesn't provide that immediate feedback. You don't consume 30 grams of protein at lunch and suddenly climb hills faster that afternoon. Instead, protein works quietly in the background, influencing how effectively the body responds to weeks and months of training. 

A large systematic review and meta-analysis by Lin et al. (2021) examined the effects of protein supplementation in endurance athletes. Across multiple studies, athletes consuming additional protein alongside endurance training demonstrated greater improvements in aerobic capacity, peak power output and time-trial performance compared with training alone. Perhaps most importantly, they also showed improvements in lean muscle mass and recovery, both of which underpin long-term endurance performance. 

This highlights an important distinction. Protein doesn't directly make you faster in the way carbohydrate can improve performance during a ride. Instead, protein appears to enhance the adaptations that occur because of training. Over time, these adaptations accumulate into improved fitness, greater resilience and ultimately better performance. In many ways, carbohydrates determine today's ride. Protein helps determine next month's performance. 

This becomes even more important when body composition goals enter the equation. Many cyclists spend at least part of the year trying to reduce body weight. Whether preparing for a sportive, targeting a hill climb or simply attempting to improve power-to-weight ratio, calorie deficits are common within endurance sport. Unfortunately, when calories are reduced, the body doesn't automatically lose fat alone. 

Without sufficient protein, weight loss often includes a significant amount of lean muscle tissue. This is problematic because muscle is not simply there to produce power. It also acts as a reservoir of glycogen, contributes to metabolic health, supports injury resilience and helps maintain overall athletic performance. Numerous studies have shown that higher protein intakes help preserve lean tissue during periods of calorie restriction, allowing athletes to lose a greater proportion of fat while retaining the muscle they've worked so hard to build. Put simply, protein helps ensure that when weight is lost, it is more likely to come from the places you want to lose it. 

The importance of protein becomes even greater as we age. Many club cyclists and runners are now in their forties, fifties and sixties. While endurance performance can remain remarkably high into later life, the body's response to protein changes over time. Researchers refer to this as anabolic resistance. As we age, muscles become less sensitive to the normal stimulatory effects of dietary protein, meaning older athletes often require more protein to achieve the same muscle protein synthesis response that a younger athlete would obtain from a smaller serving. 

The implications extend far beyond sporting performance. Preserving lean muscle tissue is associated with improved metabolic health, greater independence, reduced injury risk and healthier ageing overall. Protein therefore occupies a unique position within endurance nutrition. It supports performance, but it also supports health. It contributes to recovery, but it also helps maintain strength and function as we grow older. 

When discussing performance nutrition, it is easy to become obsessed with what happens during a ride. We debate carbohydrate intake, hydration strategies, caffeine doses and electrolyte concentrations. Yet these interventions largely influence performance on a given day. Protein influences the athlete you become. The adaptations from training. The quality of your recovery. The preservation of muscle mass. Your ability to absorb training week after week, month after month and year after year. 

And that brings us back to where we started. Performance nutrition is often viewed through the lens of what happens during a ride or run. The gels, sports drinks and carbohydrate calculations tend to receive all the attention. Yet that is only part of the story. The real adaptations occur afterwards, between the Strava upload and the next time you clip in.  

Carbohydrates may fuel today's ride. But protein helps build the athlete.