Subjective feelings of performance difficulty during exercise can differ from objective performance measures, even when sleep-deprived, jet-lagged, or stressed.

“subjective measures of performance are different often from objective measures of performance. And that goes for the menstrual cycle symptoms and and other factors as well. So you might go in and and deadlift the same weight as last week and you'd say, "Wow, this feels really heavy or the weight's moving really slow this morning." But you're still lifting it. So objectively, the performance was the same. It's just your experience of what it felt like differs.”