Warmups can influence how accurately you estimate your Reps in Reserve (RIR), which is the number of repetitions you believe you can still perform before reaching failure during a set. When you warm up properly, your muscles become more prepared, your nervous system activates better, and your perception of effort changes. This can make your RIR estimates more reliable and sometimes lead you to feel stronger or more capable of performing additional reps than you initially thought.
Before a workout, warmups gradually increase blood flow to muscles and improve joint mobility, which reduces stiffness and enhances muscle function. This physiological readiness means that when you start your working sets, your muscles are more efficient, and your fatigue threshold is higher. As a result, you might find that a weight feels lighter or that you have more reps left in the tank than you expected based on cold or unprepared muscles.
Because RIR is a subjective measure relying on your sense of effort and fatigue, warming up helps calibrate this sense. Without warming up, you might underestimate your capacity, thinking you have fewer reps left than you actually do. Conversely, a good warmup can help you better judge how close you are to failure, leading to more accurate RIR ratings. This is especially important for experienced lifters who use RIR to autoregulate training intensity and volume.
In practice, warmups allow you to test the weight and movement pattern at lighter loads, giving your brain and body feedback on how the working weight will feel. This feedback helps adjust your expectations and RIR estimates for the heavier sets. For example, if a warmup set feels easier than expected, you might revise your RIR estimate upward, meaning you have more reps left than initially thought. If it feels harder, you might lower your RIR estimate.
Overall, warmups improve the accuracy of RIR estimates by enhancing muscle readiness and providing sensory feedback, which helps lifters better gauge their effort and fatigue levels during training.
Sources
https://rippedbody.com/rpe/
https://www.minimumviablepump.com/guides/rir
