Moderate Intensity Cardio Outperforms High Intensity Training In Decreasing Perceived Stress
“Lack of activity destroys the good condition of every human being while movement and methodical physical exercise saves and preserves it”-Plato
I stare at the pedals underneath me. The voice in the head continues to berate and demean me.“You are nothing. You need to work harder. Prove to me your worth.” I feel defeated. I rationalize skipping the workout. The thoughts echo in the head, “you deserve a day off...you don't need to train today.” The battle between the judge and the victim ensues in my head. I reason with both, “ let's just do ten minutes...ten minutes and then we can go home.” The voices quiet in agreement.
I loop the headphones around my ears to drown out the thoughts. Play..increase volume..increase volume.
“N-now th-that that don't kill me
Can only make me stronger
I need you to hurry up now
'Cause I can't wait much longer
I know I got to be right now
'Cause I can't get much wronger
Man I've been waiting all night now
That's how long I been on ya
I need you right now”
The lyrics strike a chord. The beat picks up. I start to pedal — cycle after cycle my heart rate increases. Seconds and minutes go by. Adrenaline and cortisol pump energy into the blood. Sugar courses through the veins. The lyrics continue.
“Let's get lost tonight
You could be my black Kate Moss tonight
Play secretary, I'm the boss tonight
And you don't give a fuck what they all say, right?”
Eyes dilate — focus and intensity increase. My legs feel heavy, but I push the pace and pedal harder. Oxygen depletes, and acid fills my legs. The pedals slow down. However, I am determined to complete the task at hand. I look at the timer, 5...4...3...2...1. The clock hits zero. “Fuck! That was hard, but good job.” A smile emerges. “One down...nine to go.” The voices quiet. The battle is won. The judge and the victim are silenced.
That was last week, but I remember it like yesterday. I woke up feeling like shit. My mood was depressed, and my energy was low. I didn't want to exercise, let alone move. Maybe it was due to overeating the night before or not sleeping enough. Regardless, I woke up on the wrong side of the bed. However, I had clients to train, so I couldn't just lay in bed all day. Coffee helped the sessions go smoothly, but I had no desire to exercise.
Since I am a trainer, everyone thinks I love working out, which is hardly the case. I have days where I don't want to do anything. I have to force myself to get on the gym floor. However, every time I get on the gym floor, I feel better. My energy and mood improve. I become a better person. Why is that? How does exercise make us feel so damn good?
“Exercise has such profound pharmacological and physiological effects that it should be considered a drug therapy...If exercise were a drug evaluated by the Food and Drug Administration, it might be approved for a large number of therapeutic indications...(1) “
Exercise Is A Powerful Drug
Research has shown aerobic training to improve stress resiliency, mood, memory function, quality of life, and overall well being.
“stress reduction, e.g., through exercise, has been shown to involve serotoninergic and especially dopaminergic and neuropeptidergic signalling in the associated brain regions....the greater the stress (in combination with physical activity and exhaustion), the deeper the relief and relaxation,..(the ‘I did it’ component), when successfully solving and overcoming the stressful challenge(2).”
Put simply, exercise has drug mimicking effects. Dopamine, serotonin, and endorphins increase during moderate to high intensity training. These neurotransmitters are responsible for pleasure, calmness, and a sense of well-being. I believe this chemical cocktail was responsible for my mood change on the bike. To experience this cocktail, you need to have a heart rate of 140 to 180 beats per minute for at least 20 minutes(3).
Exercise Prescription
Exercise is my drug of choice, one I take daily. However, too much of anything can have detrimental effects. So how do we reap the benefits of exercise without burning ourselves out? The answer lies in the dose and intensity of the program.
A study done at McMaster University might have found the answer. The purpose of the study was to figure out whether or not the intensity of an exercise program played a role in reducing depression. To figure this out, 61 college students (72% female) took part in the six-week study. There were three groups: non-exercise (control), moderate intensity, and high-intensity. Both exercise groups performed cardio on a stationary bike three times a week for six weeks. The two routines can be found below (3) :
3 minute warm up and 2 minute cool down
High-intensity Group (HIT): 10 intervals x 1 min @ 80% max wattage x 1 min rest @30% max wattage
Moderate Intensity Group(MIT): 27.5 minutes at 40% max wattage
Results
Which group do you think experienced the best stress-reducing effects? I am sure you could guess it wasn’t the non-exercise group. In fact, inflammation and depression increased, while aerobic capacity decreased in that group. Whoa! I told you exercise was a powerful drug. The results of the other groups confirm this belief.
Both exercise groups increased aerobic capacity and decreased depressive symptoms. However, perceived stress and inflammatory markers ( i.e., tumor necrosis factor alpha (TNF-α), interleukin-6, and C-reactive protein) increased during the high-intensity training compared to the moderate intensity. “This may be due to the higher level of physical stress evoked by the more strenuous exercise protocol,” stated the authors.
Ultimately, the moderate intensity group obtained the best results from the study. The authors concluded,
“the results suggest that moderate-intensity exercise may be an optimal intensity of exercise for the promotion of mental health by decreasing TNF-α. This is critical for informing the use of exercise as medicine for mental health.”
Discussion
There are always going to be drawbacks to research, and this study is no different. There are a couple of issues worth highlighting. To begin, the inflammatory increase in the HIT group could be due to inadequate exposure to the training stimulus. A meta-analysis done by Ramos and colleagues found no changes in inflammation (c-reactive protein) during a 12 week HIT program (4). Also, we don't know the diet or sleep schedule of these individuals. Two factors that play a huge role in controlling inflammation.
In addition, the study had a high percentage of females (72%). There has been some research suggesting females respond better to moderate intensity workouts due to a higher type I muscle fiber percentage. Type I fibers are oxidative and have higher endurance capabilities (5). I would be curious to see what the results would be if it had a higher percentage of males. Also, the high intensity group was performing a 1-1 work to rest ratio. What if they performed a 1-2 or 1-3 work to rest ratio (i.e. 1 min on - 2 mins off)? Would they still have experienced an increase in perceived stress? Would their inflammatory markers still have increased? There are too many questions left unanswered to ditch HIT in favor of MIT.
It comes down to a multitude of factors:
How much sleep did you get the night before?
How is your nutrition?
What is your resting heart rate?
What do you prefer?
If you aren't sleeping much, eating poorly, and have a high resting heart rate (above 65 bpm), then you should do a MIT program. But if everything is on point, then a HIT could be the right choice for you.
Above all, it comes down to testing on yourself to see what works best. Regardless of your choice, any type of exercise is better than no exercise. A meta-analysis done on the effectiveness of exercise for anxiety found training to be a useful tool for combating stress (6). The authors stated,
“Taken together with the wider benefits of exercise on well-being and cardiovascular health, these findings reinforce exercise as an important treatment option in people with anxiety/stress disorders.”
They recommended 150 minutes of moderate exercise or 75 minutes of vigorous exercise per week. And yes, you can do a combination of both.