Ditch the sRPE: A Better Way to Estimate Internal Training Load?

Intro: The RPE Conundrum

The Rate of Perceived Exertion (RPE) has long been the go-to metric for coaches and sports scientists to assess internal training load. Simple and subjective, RPE invites athletes to reflect on “how hard” a workout felt, providing a seemingly straightforward way to quantify effort.

But beneath its simplicity lies a host of challenges. What does “hard” even mean? For some, it might point to how heavy their legs felt during sprints. For others, it could reflect the mental drain of decision-making drills or the lung-searing intensity of intervals. And when do you ask this question? Immediately after a workout’s toughest segment? Post-cooldown? The timing can drastically alter the answer, making RPE an inconsistent, and often unreliable, metric.

Researchers and practitioners have tried to address these shortcomings by introducing differentiated RPE (dRPE). This approach segments RPE into categories such as legs, breathing, and overall mental fatigue.

For example, after a workout, athletes might rate:

• How hard the session was on their legs.
• How hard it was on their lungs.
• How mentally demanding it felt.

While differentiated RPE provides a more nuanced view of internal load, it comes with added complexity. Athletes now need to answer multiple questions post-session, potentially introducing response fatigue or inconsistency. Some athletes might still struggle to identify and differentiate between these components, or they may give conflicting scores due to a lack of clarity about what each rating signifies.

Consider a few scenarios where traditional and even differentiated RPE can struggle:

1. Sprint Workouts vs. Interval Training:

Sprinting workouts often leave athletes with burning legs and muscle fatigue. In contrast, interval training may push the cardiovascular system to its limits. Despite these differences, both might earn the same “overall” RPE score or even confusing dRPE responses, because athletes focus on what stood out most at that moment.

2. Skill Acquisition Sessions:

Sessions focusing on tactical decision-making or technical skills can be mentally taxing but leave athletes feeling physically fresh. Traditional RPE often fails to account for this. Differentiated RPE can help, but athletes may still struggle to quantify mental effort or undervalue its importance compared to physical fatigue.

3. Highly Emotional Events:

Emotional stress can amplify perceptions of effort, leading to inflated RPE or dRPE scores. Conversely, a highly motivating environment might deflate scores, even when the workout was physically challenging. These emotional factors can influence multiple dRPE categories, muddying the data.

4. Order of Workout Elements:

Differentiated RPE might capture specific components better, but when the RPE question is asked—whether during the peak of intensity or after recovery—can still drastically skew results, particularly for workouts with varying demands across segments.

So, while dRPE is a step in the right direction, it doesn’t fully resolve the underlying problem of subjective complexity. Is there a way to capture the multidimensional nature of internal load without overburdening athletes with a long list of questions?

From RPE to Repeatability—A Speculative Solution

One intriguing alternative comes from borrowing the Net Promoter Score (NPS) concept, commonly used in business. Instead of asking, “How hard was this workout?” or breaking it into multiple components, we could ask: