Whether you want to maximize a weight lifting session or a cardio-strength combo workout, research shows the answer is yes: order matters.
Let’s look at the cardio-strength combo first. If you’re planning to run and lift in one training session, for example, a 2012 study published in the Journal of Strength and Conditioning Research suggests you should run before lifting.
In the study, 10 men in their early 20s rode a stationary bike for 30 minutes at moderate intensity, and performed three sets of eight repetitions of various strength exercises. Researchers collected blood samples before, during, and after the workout, testing for testosterone and cortisol levels. Testosterone is a hormone that, among other things, aids muscle recovery and growth. Cortisol, on the other hand, breaks down muscle.
Researchers found that the men who cycled before lifting had significantly higher levels of testosterone in their blood after completing the entire bike-lift workout than the men who lifted first, then cycled. The study concludes that testosterone production—and therefore muscle recovery and growth—is maximized after completing a cardio-first, strength-second workout. (These findings only apply when doing a shorter, moderate-intensity cardio workout before strength training.) So, if you're hitting the gym, throw in a good 20- to 30-minute cardio warmup before lifting weights to maximize strength gains and speed up recovery.
If you’re just doing strength exercises, research suggests you should consider the order in which you do these as well. Studies have found that research subjects were able to do the most repetitions of the first strength exercise they performed. Subjects also posted their greatest strength gains in the first muscle(s) they worked during their training sequence. This led researchers to conclude that strength exercises should be performed in order of their importance to overall fitness goals. If you want killer quads for cycling power, for example, start your strength routine with some wall sits. If you're most concerned with lower back strength, start with back extensions and save those wall sits for later.