When you enter the gym, which way should you head first? Toward the
treadmills and spin studio to get your sweat on with a cardio session?
Or toward the free weights and strength-training machines to do some
resistance training?

The American College of Sports Medicine suggests doing both types of exercise
to take advantage of their unique benefits for improving health and
daily functioning and reducing chronic disease risk. But what is the
optimal sequence to get the best results?

The answer to this question is … it depends. I’m an exercise physiologist.
Recently in my lab we have been studying the effects of combinations of
aerobic and resistance training on improving health-related fitness,
particularly aerobic capacity and muscular strength.

Research suggests that when you’re designing your exercise program,
there are a few factors to take into account, including your age,
fitness level and exercise history and goals. You’ll also want to
consider the volume of your exercise routine – that is, its duration and
intensity – and how you’ll schedule your training during the day.

Benefits of exercise

First, just about any exercise at all is going to be better for you than doing nothing.

Aerobic exercise
is rhythmic activity that gets your heart pumping. Examples are
walking, running, swimming, cycling and using a cardio machine such as
an elliptical trainer.

Aerobic exercise can improve cardiorespiratory function – over time,
your heart and lungs get better at delivering oxygen to your muscles to
make energy for continued muscle contractions. Aerobic exercise can also
reduce several chronic disease risk factors, increase how much energy
your body uses and how much fat it burns, and improve physical and
cognitive function.

Resistance training
involves strengthening your muscles by lifting, pushing or pulling
against resistance. This type of exercise can be done using free-weight
barbells, dumbbells, kettlebells, weight machines or even elastic bands.

Resistance exercise improves muscular strength, endurance and the power and the size of muscles – what exercise physiologists call muscle hypertrophy. Studies show resistance training has health-related benefits, as well, particularly for people who have or are at risk of developing Type 2 diabetes.
It can improve blood pressure, blood levels of glucose and the ability
of muscles to use glucose for energy, and it helps maintain lean body
mass and bone health.

Training for health benefits

With a limited amount of time to devote to working out, many people
include both cardio and weights in the same exercise session. This
concurrent training comes with plenty of benefits for your health,
including lowering your cardiovascular and metabolic risks.

In fact, doing both forms of exercise together
is better, especially for people with chronic disease risk factors,
than exercising for the same amount of time but sticking with just
aerobic or resistance exercise.

Studies of concurrent training suggest a generalized training effect –
similar improvements in aerobic capacity and muscular strength,
regardless of the order of aerobic and resistance exercises in a
session. These benefits hold for a wide variety of people, including those who are initially inactive, recreationally active, young people and older women and men.

Resistance exercise done before aerobic exercise results in a small increase in lower-body muscular strength without compromising all the other improvements in health-related physical fitness.

So if your exercise goals are along the lines of staying generally healthy and enjoying the mental benefits of moving your body,
resistance training first might provide a little boost. Research
suggests that overall, though, you don’t need to worry too much about
which order to focus on – cardio versus weights.

Training with performance goals in mind

On the other hand, you may want be more thoughtful about the order of
your workout if you’re a performance-oriented athlete who is training
to get better at a particular sport or prepare for a competition.

Research suggests that for these exercisers, concurrent training may
slightly inhibit improvement in aerobic capacity. More likely, it can
hinder gains in muscular strength and power development, and to a lesser
degree muscle growth. This phenomenon is called the “interference effect.” It shows up most in well-trained athletes undertaking high volumes of both aerobic and resistance exercise.

Researchers are still investigating what happens on a cellular level
to cause the interference effect. Aerobic and resistance training
unleash competing influences at the molecular level
that affect genetic signaling and protein synthesis. At the start of an
exercise program, the body’s adaptations are more generalized. But with
more training, the muscle changes become more and more specific to the
kind of work being done, and the likelihood of the interference effect
kicking in increases.

Of course, many sports require combinations of aerobic and muscular
capabilities. Some elite-level athletes need to improve both. So the
question remains: What is the optimal order of the two modes of exercise
to get the best performance effects?

Given research findings about concurrent training for high-level athletes,
it makes sense to do resistance exercise first or to train first in the
type of exercise that is most important to your performance goals.
Additionally, if possible, elite athletes should give their bodies a
break of at least three hours between resistance and aerobic training
sessions.

Don’t sweat the order

In my lab, we’re studying what we call “microcycles” of aerobic and
resistance exercise. Instead of needing to decide which to do first, you
weave the two modalities together in much shorter bursts. For instance,
one set of a resistance exercise is immediately followed by three
minutes of walking or running; you repeat this cycle for as many times
as necessary to include all of the resistance exercises in your routine.

Our preliminary findings suggest this method of concurrent training
results in similar gains in aerobic fitness, muscular strength and lean
muscle mass – while also feeling less challenging – when compared with
the typical concurrent routine where all of the resistance exercise is
followed by all of the aerobic exercise.

For most people, my current advice remains to choose the order of
exercise based on your personal preferences and what will keep you
coming back to the gym. High-level athletes can avoid any significant
interference effect by doing their resistance routine before the aerobic
routine or by separating their aerobic and resistance workouts within a
particular day.