When you’re not sleeping well, your body and mind suffer. Your muscles feel weak, your focus disappears, and even simple tasks become harder. Many people wonder if they should still exercise when sleep is poor, and if so, how hard they should push. This is where the concept of reps in reserve becomes important.
Reps in reserve, often called RIR, refers to how many more repetitions you could theoretically do before reaching complete muscle failure. For example, if you do 8 repetitions of an exercise but could have done 12 before your muscles gave out, you have 4 reps in reserve. This concept helps you control how intensely you’re working during your workout.
When you’re sleeping poorly, your body is already stressed and fatigued. Your nervous system hasn’t recovered properly, your hormones are out of balance, and your muscles haven’t fully repaired from previous workouts. Pushing yourself too hard in this state can make things worse. This is where keeping reps in reserve becomes a smart strategy.
Exercising at moderate to vigorous intensity for 30 to 45 minutes at least three times per week significantly improves sleep duration and reduces nighttime awakenings[4]. However, this guidance assumes you’re already sleeping reasonably well. When sleep is poor, the approach needs adjustment.
The relationship between exercise and sleep works both ways. Exercise helps regulate your sleep-wake cycle and deepens your sleep, which improves energy levels and mood[2]. But if you’re already sleep deprived, intense exercise can actually interfere with recovery. Your body needs energy to repair itself, and if you’re not sleeping well, you don’t have that energy to spare.
Resistance training shows particular promise for improving sleep. A study of college students with primary sleep disorders found that a 3-month resistance exercise program improved sleep latency, total sleep time, sleep efficiency, and daytime function[1]. Another study showed that 42 percent of participants who were getting less than seven hours of sleep per night and did resistance exercise were able to prolong their average sleep time by 17 minutes per night[2]. These results are encouraging, but they came from people who maintained consistent routines over weeks and months.
The key insight from research is that consistency matters more than intensity. One study of sedentary adults with insomnia showed that participants who exercised 30 to 40 minutes four days a week for 16 weeks experienced noticeable improvements in sleep quality[3]. Importantly, these improvements didn’t happen immediately. In the initial weeks, poor sleep actually interfered with their ability to exercise. Only through consistent effort did their sleep patterns gradually improve[3].
This finding reveals why reps in reserve is useful when you’re sleeping poorly. If you push yourself to complete failure during every workout while sleep deprived, you risk overtraining and making sleep worse. Your body becomes more stressed rather than less stressed. By keeping reps in reserve, you maintain a sustainable exercise routine that your body can actually recover from, even with poor sleep.
When you keep reps in reserve, you’re essentially exercising at a moderate intensity rather than maximum intensity. This allows your body to adapt to the stimulus without overwhelming your already-compromised recovery systems. You can maintain consistency without crashing, which is exactly what the research shows leads to better sleep over time.
Exercise improves sleep through multiple mechanisms. It increases the release of endorphins, which are feel-good hormones that improve relaxation[2]. Physical activity increases melatonin release from the pineal gland, making it easier to fall asleep[6]. Exercise also promotes more time in deep sleep phases, the most restorative sleep stages[3]. Additionally, exercise may work through the gut microbiota, with physical activity enhancing sleep through thermoregulatory changes, stress reduction, better mood, and strengthened immune responses[5].
The practical takeaway is straightforward. When you’re sleeping poorly, don’t abandon exercise, but adjust how you approach it. Use reps in reserve to keep your workouts sustainable. Aim for moderate intensity rather than maximum effort. This might mean stopping 2 to 4 reps before failure instead of pushing to complete exhaustion. Maintain consistency with 3 to 4 workouts per week rather than sporadic intense sessions. Over weeks and months, this approach allows your sleep to gradually improve while you continue benefiting from exercise.
Your body is a system in balance. When sleep is poor, that balance is already disrupted. Intense exercise adds more disruption. Moderate exercise with reps in reserve provides the stimulus your body needs to improve sleep without pushing you further into a hole. The research clearly shows that people who maintain consistent, moderate exercise routines eventually sleep better. Reps in reserve is the tool that makes this consistency possible when sleep is already compromised.
Sources
https://pmc.ncbi.nlm.nih.gov/articles/PMC12531955/
https://www.runstreet.com/blog/exercise-and-sleep
https://amerisleep.com/blog/exercise-and-sleep/
https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2025.1639099/full
