One may not run for exercise on Shabbat, because it is burdensome rather than pleasurable. Even though people who work out enjoy it, this enjoyment derives from their awareness that they are taking care of their health and physical fitness, not from the exercise itself. Even one who is very fit, runs every day, and enjoys it may not run on Shabbat, because it is a weekday activity. It will appear to others that he is belittling Shabbat and treating it like a weekday. However, one who enjoys exercise may jump or work out for pleasure inside his home on condition that he does not overexert himself, does not follow a regimen, and does not use special equipment, any of which would be deemed a weekday activity. One may not play ball for the same reason; even children may not play with a ball that adults use for sports, because it is a weekday activity.
One may walk on Shabbat for one’s health, on condition that he walks regularly and not more briskly or more intensively than usual. Although one may not address medical needs on Shabbat, since it is not discernible that his walking has a medical purpose, and many people take walks, he may walk for health and fitness on Shabbat (MB 301:7). One may also do gentle stretches in order to loosen up.
The later poskim agree that one may not ride a bicycle on Shabbat. Some maintain that the reason for this prohibition is a concern that one will travel outside the teĥum, while others say that the concern is that the bicycle will break and he will end up fixing it. In fact, the main reason is that it is a weekday activity, since people ride bicycles primarily to travel to work or to exercise.
. According to Or Le-Tziyon 2:36:12, exercise is forbidden only when undertaken in order to sweat to improve health, but one may run for callisthenic exercise just as youths may run for pleasure (based on Rambam, and as opposed to Rashi; see BHL 328:42). However, in practice, it would seem that exercise is, in some way, a weekday activity, as we can see from t. Shabbat 17:16, which states: “One may not run on Shabbat for exercise; but walking in the usual fashion, even all day long, is no problem.” Even though youths who enjoy running may run, this is because they enjoy the running itself; but when the pleasure is derived from improving one’s health, it is prohibited. This is made explicit in SA 301:1-2; Taz ad loc. 1; AHS ad loc. 44. It is also the position of Tzitz Eliezer 6:4 and SSK 34:22. One who enjoys the exercise itself may exercise (Melamed Le-ho’il, OĤ 53; R. Shlomo Zalman Auerbach in SSK ch. 16 n. 106) on condition that he does not do so in an organized and professional way, which would qualify it as a weekday activity. It would also seem that an adult who enjoys running may not run outside, because it seems to belittle Shabbat and is consequently deemed a weekday activity. See Harĥavot.
. However, Ben Ish Ĥai permits riding a bicycle. It explains that we need not be concerned that people will mistakenly conclude that one may ride in vehicles drawn by humans or animals. Furthermore, we do not have the right to enact new decrees (Responsa Rav Pe’alim 1:25). Nevertheless, almost all poskim are stringent, for the reasons mentioned above (Ketzot Ha-shulĥan §110, Badei Ha-shulĥan §16; Yaskil Avdi 3:19; Tzitz Eliezer 7:30; She’elat Yaakov §45; Kaf Ha-ĥayim 404:8; SSK 16:18). Or Le-Tziyon 2:42:1 adds that though it is technically possible to permit, since the widespread practice is to forbid bike riding, it is forbidden.
Those who maintain that riding a bicycle is a weekday activity can find support in Beitza 25b: “The Rabbis taught: The blind do not go out [on Yom Tov] with their canes, nor do we go out with a chair.” Rashi explains that since canes were considered weekday items, going out with them would belittle Yom Tov. He adds that the chair in question is a sedan chair (litter) carried by people. The Gemara specifies that the prohibition on carrying the chair applies when people lift it up on their shoulders (as opposed to holding it lower down). Rashi explains that when a chair is carried on the shoulders it looks like a weekday activity, it is more public, and it indicates that the chair is being carried further.