Do the activity that matters most while you are freshest, especially when both are completed in the same session.
Strength goal: lift first
If building strength or muscle is the priority, complete resistance training before hard cardio. You will have more energy and coordination for the exercises where load and technique matter.
A short easy warm-up is different from a demanding cardio session and can still come first.
Endurance goal: cardio may lead
If you are preparing for a running or cycling event, the key endurance session may deserve first position. Strength can follow or happen on a different day.
Your priority determines the order, not a universal rule.
Separate demanding sessions when possible
Hard intervals and heavy lower-body lifting can compete for performance in the same session. Placing them on different days or several hours apart may improve the quality of both.
Easy walking or low-intensity cycling is usually easier to combine.
Do not overcomplicate general fitness
For someone training for health and body composition, a full-body strength workout followed by a short cardio block is perfectly reasonable. Another day can include longer aerobic work.
This article provides general education and does not replace individualized medical care. Speak with an appropriate healthcare professional before beginning exercise if you have symptoms, significant health concerns or medical restrictions.