Short answer
No. Running, lifting weights or any exercise does not break wudu, and sweat is pure. Wudu breaks during exercise only if one of the usual causes happens, such as passing wind, blood flowing from an injury (in the Hanafi school), or fainting.
Physical effort and sweating do not break wudu. During sport, wudu is broken only by the normal breakers, such as wind, flowing blood, a mouthful of vomit, or losing consciousness.
The four schools agree on this.
Explanation
Nothing in exercise itself breaks wudu (ablution). Sweat is pure, and being tired, out of breath or flushed has no effect. So you can make wudu, go for a run, and pray when you come back, if nothing else happened.
Things that can happen during sport and do break wudu:
- Passing wind, which is common in some exercises: wudu is broken only if you are sure.
- A cut or graze that bleeds so the blood flows, in the Hanafi school (see bleeding).
- Fainting or blacking out, even briefly.
- Vomiting a mouthful after hard effort, in the Hanafi school (see vomiting).
Questions people ask at the gym:
- Touching sweaty equipment does not break wudu, and other people's sweat is pure.
- Lying on your back for exercises has no effect on wudu.
- A nap on the mat after a workout, lying down, does break wudu (see sleep).
Praying in your gym clothes is fine if they cover the awrah properly and have no impurity on them. The four schools agree that exercise and sweat do not break wudu; they differ only on side issues like blood. See sweating and wudu.
The evidence
Sahih al-Bukhari 137
Sahih... لا ينصرف حتى يسمع صوتا أو يجد ريحا ...
"He should not leave until he hears a sound or notices a smell."
Wudu stands until a real breaker is certain, such as wind you are sure of; effort and sweat are not breakers.
Where the ruling is recorded
- Nur al-Idah with Maraqi al-Falah, Kitab al-Taharah, section on what does not break wudu. Lists things that do not break wudu.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.