Conquering both the resistance and cardio sections of the gym in one workout may seem like a daunting task, but if you're strategic about your approach you can make it work. The first thing you need to decide is where to start.
Your best bet is almost always to start in the weight-lifting section. If you start your weight workout fresh, you're at less risk for an injury and you can put more effort into lifting weights.
After a proper warmup, your energy levels are at their peak. Your muscles are fueled up and ready to start a workout. Head to the weight-lifting section and start with the most complicated exercises first.
The most complicated exercise in your workout is the one that involves the most movement with your body. It's also usually the exercise where you use the most weight. The squat, deadlift, clean and bench press are examples of complex exercises that require a lot of attention to avoid injury.
Cardio exercises, on the other hand, typically don't require the same amount of focus. Running, swimming, biking and rowing are all repetitive activities. Once you get into a rhythm with these exercises they become automatic and you can focus on other things, like regulating your breathing.
Since weight-lifting exercises require more focus on proper technique to avoid injury, you should do them first. If you do your cardio exercises first you might not have as much energy to focus when you lift weights. You'll be at a greater risk for making a dangerous mistake.
In addition to draining your focus, cardio workouts tax your muscles and use precious fuel. That makes your muscles less capable of reacting during a weight lifting exercise to help you balance. It can also cause you to compensate for the tired muscles. For example, if your legs are tired from running you might try to lift a weight from the ground using your back more than your legs.
Besides avoiding injury, lifting weights before doing cardio helps you get the most out of your weight lifting workout. When you lift weights you need to tax the muscles to make them grow or get stronger. That means you need to add weight, reps or sets.
To up the difficulty of your weight lifting workout you need energy and motivation, both of which will wane if you do a cardio workout first. Keep that energy for your weight lifting exercises.
According to a 2013 study in GeroScience, lifting weights before doing cardio increases your strength gains when compared to the opposite order. In the small study, which was performed on an elderly population, the subjects either lifted weights then did a cardio workout, or vice-versa.
The group that did weights before cardio increased their strength more. That's because cardio exercises detract from your ability to push your limits when you're lifting weights. Even though the study was performed on an elderly population, it has some carryover to younger people.
Finishing Your Workout
After your weight-lifting workout, move onto the cardio section. This section of your workout isn't necessarily going to be any easier, but it won't require the same amount of intense focus on form.
As you do your cardio workout you might notice that your muscles are more fatigued than normal from weight training. Going into your cardio workout with your muscles already fatigued will make the workout more difficult.
Thankfully, cardio exercises aren't as inherently dangerous as weightlifting exercises, which is why it's less dangerous to do them when you're fatigued.
Whether you do cardio or weight lifting first also depends on your goals. If you really want to get better at cardio, then your workout should start there. Afterwards, you can lift weights to help strengthen your muscles for cardio.
If you want to gain muscle or get stronger, lifting weights first is best because you can put most of your energy towards that. If you don't have a clear goal, however, stick to lifting weights first.