HIIT Your Hormones

Research indicates that high-intensity interval training is one of the best activities for fat burning, but new research also indicates that it affects the primary hormones that drive your physiology — and which can make or break your results.

Oh hormones — they peak and dip at the most inconvenient times, affecting every aspect of your life, from mood and sex drive to fertility and metabolism. But what affects your hormones? As it turns out — exercise.

“Hormones are like tiny traffic cops directing biochemical messages that regulate everything,” explains Hayden Steele, CSCS, NSCA, CSCCA, and developer of the Shock: Women’s Fitness app. “One of the best-known natural ways to promote hormonal balance is through exercise, and through intensity-based training, women can unleash the power of the key hormones that will help them reach their fitness goals.”

High-intensity interval training has been nearly researched to death when it comes to its metabolic and fat-burning prowess, but recent results indicate that HIIT is arguably more important for women than it is for men. “Women are at a hormonal disadvantage for building muscle because they produce less testosterone,” Steele says. “But women can overcome this by training in a way that maximizes hormone levels, burning fat, building muscle and creating a lean, athletic and feminine physique.”

5 Hormones to Know

Though innumerable bodily compounds are impacted by physical activity, there are five key hormones you should take note of when it comes to performance and physique results.

Estrogen

This hormone is produced in the ovaries and plays a major role in menstruation, pregnancy, bone strength and mood regulation. “Having the right amount of estrogen actually improves fat loss because it increases insulin sensitivity, decreases cellular fat storage and can suppress appetite,” Steele says. Estrogen also stimulates the production of human growth hormone (HGH), which upregulates fat burning.

The trick is that estrogen levels need to be balanced, which becomes more difficult the closer one creeps to menopause; here, estrogen production decreases while testosterone is maintained. “This imbalance results in a reduced sensitivity to insulin, which leads to belly-fat storage,” Steele says.

Short-duration, high-intensity circuit training is the perfect foil to decreasing estrogen because it causes a huge increase in HGH, helping women burn fat, build muscle and control blood sugar.

Human Growth Hormone

Secreted by the pituitary gland at the base of your brain, HGH facilitates lipolysis, increases bone strength and stimulates muscle growth. “Growth hormone also facilitates protein synthesis for faster recovery and regulates fat metabolism,” says Steele, adding that an HGH deficiency can lead to the accumulation of body fat. “Because women produce less testosterone, they depend more on growth hormone to build lean muscle and metabolize fat.”

Mounting evidence suggests that HIIT is one of the most effective workouts to boost HGH response — specifically in women. “Women have a higher release of HGH in response to intense exercise than men, likely due to higher estrogen levels,” Steele says. Workouts that leave you breathless, cause that “burn” and push your limits physically will amplify HGH response, he adds.

Testosterone

Contrary to popular belief, women do produce testosterone, just in smaller amounts than men. This hormone plays a key role in the development and maintenance of muscle size and strength and energy levels and bone density. It also works to reduce fat stores, specifically in the abdomen. “For women, the maintenance of bone density and muscle mass is important, as both tend to deteriorate with age,” Steele says.

Research suggests that high-intensity exercise stimulates testosterone production, and Steele says lifting heavier weights to elevate intensity is one of the best natural solutions for women to combat low or declining testosterone. Also, consider some lifestyle changes. “There are several potential causes for testosterone deficiency, among them the use of birth control pills, antidepressants, soy milk, a vegetarian diet or other psychological factors,” Steele says.

Cortisol

Cortisol is a Jekyll and Hyde hormone — as good as it is for some things, it is equally as bad for others. Cortisol rises with the onset of anxiety and tension, subsequently reducing insulin sensitivity and impairing your ability to burn fat and build muscle. If cortisol remains chronically high, your blood sugar and blood pressure will rise, you’ll store more calories as fat and your immune system will be suppressed. You also may feel wired or anxious in the evening, making it hard to sleep.

But on the Hyde front, cortisol is required for optimal health and can actually burn fat under the right circumstances: Growth hormone and catecholamines (dopamine, epinephrine and norepinephrine), which rise during exercise, can accentuate the ability of cortisol to burn fat while suppressing its potential to store it. Short, intense bouts of exercise serve to elevate cortisol as well as HGH and catecholamines. “You want cortisol to be high during exercise,” Steele says. “Catecholamines work synergistically with cortisol and other fat-burning hormones to aid in the release of fat, especially abdominal and visceral fat.” 

Irisin

Irisin is often referred to as the “exercise hormone,” serving as a link between exercise and its benefits by increasing energy expenditure and reducing insulin resistance. “Irisin helps rewire your body to battle fat,” Steele explains. “It activates the genes that transform white fat — inert, stored calories — into brown fat — metabolically active, calorie-burning tissue. Irisin also increases the ability of your fat cells to burn calories at rest while also preventing new fat cells from forming.”

Normally, your body produces only small quantities of irisin, but exercise — specifically intense interval training — boosts its production: Research done with women shows that single afternoon sessions of both moderate-intensity and HIIT training raised irisin levels by 12 percent. 

HIIT Your Hormones

It’s clear that HIIT is the secret to hacking your hormones, and your emphasis should be on intensity. “Your workouts need to be challenging, increasing your heart rate and making you sweat,” Steele reminds. Keep your rest between sets or circuits to 60 seconds or less to maximize hormonal response, and on heavier days when you train in a rep range of eight or below, extend your rest periods to two to three minutes. “Also, keep your training session under an hour — any longer will have diminishing returns,” Steele says. “Besides, if you have energy left after an hour of training, you’re not working hard enough!”

Here are three styles of training that can work your hormones to your advantage. Try the sample workouts or create your own using these HIIT templates to hit your goals.

Circuit Training

To make the most of your time and optimize your hormonal response, Steele recommends circuit training with a focus on compound movements. “Compound lifts burn more calories and cause greater spikes in heart rate because they involve multiple muscle groups,” Steele says.

On total-body workout days, alternate between upper- and lower-body lifts to increase intensity, for example, squats followed by push-ups. On upper- or lower-body days, alternate between agonist/antagonist lifts (e.g., push/pull motions) or superset a lift with a core exercise to push your limits. 

Full Body Workout 1

Warm-Up: Perform each move for 30 seconds. Complete two rounds.

• Bodyweight Squat
• Plank
• Bicycle Crunch

Workout: Perform the moves back-to-back for 30 seconds each. Complete two total rounds of each circuit, and rest one minute between rounds.

Full Body Workout 2

Warm-Up: Jump rope for three minutes.

Workout: Perform these moves back-to-back for 45 seconds each. Complete two total rounds of each circuit, and rest one minute between rounds.

Tabata Training

A Tabata is a style of circuit training in which you alternate 20 seconds of all-out work with 10 seconds of rest for eight rounds, or a total of four minutes. Research has shown Tabatas to be one of the most effective ways to boost metabolism and incite hormonal response with this caveat: Those 20 seconds of work must be done at absolute maximal effort. Otherwise, they simply become moderate-intensity intervals — which is not a bad way to train, but they don’t have quite the same impact as a redlining Tabata.

Traditionally, a Tabata is done at the end of a workout to finish off a particular muscle group or groups. And though you can combine more than one Tabata together, if you’re actually putting in your max effort during the first one, chances are those four minutes will be plenty. 

Tabata 1

Complete four rounds of the following workout:

Tabata 2

Complete eight rounds of the following workout:

Tabata 3

Complete two rounds of the following workout:

Percentage of One-Rep Max (IRM)

The best way to get lean and improve muscle tone is to train with weights that make you a little uncomfortable. OK, maybe a lot uncomfortable. “Studies specific to women show that important metabolic hormones are responsive to moderate and heavy exercise routines having three to 12 repetitions with varying weight loading between 65 and 85 percent of their one-rep max,” Steele says. “Heavy sets with fewer reps — five grunting reps is where a lot of the magic happens.” Here’s how to calculate the weight you should be lifting to get the most from your heavy workouts.  

Strength Workout 1: Lower Body — Back Squat

Warm-Up: Do each move for 30 seconds. Complete three rounds.

• Bodyweight Squat
• Cossack Squat
• Run 200 meters

Workout:

Finisher (optional): 6-Minute 3EMOM

Cycle through these moves, performing one per minute for three minutes. Complete two rounds.

• Walking Lunge
• Bear Crawl
• Wall Sit

Strength Workout 2: Upper Body — Push Press

Warm-Up: Do each move for 30 seconds. Complete three rounds.

• Arm Circles Forward
• Arm Circles Backward
• One-Arm Dumbbell Overhead Press (right arm)
• One-Arm Dumbbell Overhead Press (left arm)
• Row 100 meters

Workout:

Finisher (optional): Go through each superset two times. Rest as needed.

Body Fat in Balance

Ironically, the amount of body fat you carry can actually determine your fat-burning potential.

More Body Fat = More Estrogen

Fat cells contain an enzyme called aromatase, which helps convert testosterone to estrogen. A higher percentage of body fat means an overproduction of estrogen and a reduction in testosterone.

Less Body Fat = Less Estrogen

Women with extremely low body fat may have problems producing enough estrogen because there are fewer fat cells to produce aromatase, resulting in low estrogen levels.

Estrogen Rx:

• Balance your caloric intake with your activity level to maintain a healthy body-fat percentage and promote hormonal balance. Ideally, female athletes should fall between 14 and 20 percent body fat and generally fit women between 21 and 24 percent. (Obese women are categorized as 32 percent and above.)
• Eat clean, eliminate added sugar and procure the majority of your carbs from vegetables and some fruits. Also, eat plenty of broccoli and cauliflower, Hayden Steele advises. “These veggies contain a compound that promotes estrogen metabolism.”
• Prioritize strength training over cardio. “Resistance training helps preserve hormonal balance and will keep growth hormone levels elevated,” Steele says.
• Add some HIIT training to your routine to improve body composition while promoting optimal hormonal balance.

Signs of Estrogen Deficiency:

• Irregular/absent periods
• Hot flashes
• Breast tenderness
• Painful sex
• Mood swings
• Headaches
• Depression
• Fatigue
• Difficulty concentrating

Signs of HGH Deficiency:

• Reduced lean body mass
• Increased insulin resistance
• High blood pressure
• Elevated triglycerides
• Fatigue
• Reduced sex drive
• Difficulty concentrating
• Sensitivity to heat and cold
• Anxiety and/or depression
• Fibromyalgia
• Decreased bone density

Signs of Excess Cortisol:

• Rapid weight gain
• Flushed face
• Muscle weakness
• Headaches
• High blood pressure
• Severe fatigue
• Mood swings
• Frequent urination

Signs of Cortisol Deficiency:

• Fatigue
• Dizziness, especially upon standing
• Weight loss
• Muscle weakness
• Mood changes
• Darkening of certain areas of skin

Signs of Low Testosterone:

• Fatigue
• Reduced sex drive
• Poor sleep
• Fertility issues
• Irregular menses
• Vaginal dryness
• Bone loss (osteoporosis)
• Weight gain
• Muscle atrophy
• Increased abdominal fat