The 40+ HIIT Protocol: Dr. Sims' Exact Sprint Interval Training (SIT) and Resistance Scheduling (Sets, Rest, Frequency)

For women over 40 (perimenopause onward), the decline of estrogen significantly reduces a powerful anti-inflammatory and anabolic agent, making it crucial to use highly intense, specific training to compensate. HIIT and Sprint Interval Training (SIT) protocols are essential because they create an external stress strong enough to drive favorable metabolic and hormonal adaptations, such as promoting an anti-inflammatory response in the muscle cell (mimicking estrogen's former role) and stimulating lactate production for brain health.

The consensus from longevity experts is that women over 40 should polarize their training—focusing on heavy strength work and true high-intensity intervals, while avoiding the "moderate intensity middle ground" (like many cardio classes) that drives up cortisol without invoking the post-exercise hormonal response (growth hormone, testosterone) needed to dampen that stress.

The audience is confused because two different types of high-intensity training protocols were described—traditional HIIT (longer work periods) and Sprint Interval Training (SIT) (maximal effort, short duration)—and they are unsure which to prioritize, what the exact scheduling is for women over 50, and whether this intense work can be combined with heavy lifting without compromising recovery or increasing injury risk. Many feel that general guidance is not specific enough for their age group.

For women 40+, prioritize heavy resistance training (3–4 times per week) as the bedrock, and integrate Sprint Interval Training (SIT) 1–2 times per week. SIT requires maximum effort for short bursts, followed by long recovery periods, which is metabolically distinct and superior to moderate-intensity HIIT programs.

Dr. Stacy Sims
Dr. Sims provided detailed, female-specific protocols, distinguishing between different forms of high-intensity training:

• Training by Age Group: For women aged 40–50 and 50+, the training emphasis must be on heavy resistance training and true high-intensity work. This combination helps mitigate the rapid physiological changes of perimenopause (such as increased visceral fat and soft tissue injury risk).
• Defining True High-Intensity: True high-intensity work is defined as either:
  1. High-Intensity Interval Training (HIIT): 1–4 minutes of hard work at 80% or more of max effort, with variable recovery. (Example: Running 400m–800m repeats on a track, recovering by walking/jogging half a lap).
  2. Sprint Interval Training (SIT): 30 seconds or less of full gas (110%, or a 9 or 10 on perceived exertion) on a mode of activity like a rower, bike, running, or battle ropes.
• The SIT Protocol (Specifics): When performing SIT (30 seconds all out), the subsequent rest period should be 2–3 minutes of recovery. This long recovery is necessary to regenerate ATP and allow the central nervous system to recover enough to be able to go "all out again," not just moderately hard. This cycle (30 seconds maximal effort, 2–3 minutes rest) should be repeated 4–6 times.
• Scheduling and Frequency: Women 40+ should include 1–2 HIIT or SIT sessions per week. This true high-intensity work should not be stacked two days in a row to ensure recovery from the significant stress on the body.
• Combining Workouts: She gave an example of combining strength and SIT: doing a 20-minute lower body heavy set followed by immediate SIT sessions on an Assault Bike.

Dr. Rhonda Patrick
Dr. Patrick (via host discussion) focused on general HIIT protocols, not specifically female 50+, but contributed gold-standard recommendations for improving cardiorespiratory fitness (VO2 max) in older adults:

• Vigorous Intensity: Exercise must be vigorous intensity, where the heart rate is up to about 80% of max heart rate and you are unable to have a conversation.
• Norwegian 4x4 Protocol (Gold Standard): This is highly effective for robust improvement in cardiorespiratory fitness.
  ◦ Work: 4 minutes as hard as you can maintain (not all out).
  ◦ Recovery: 4 minutes of light exercise (e.g., walking, going very slow on a bike).
  ◦ Sets: Repeat this cycle 4 times.
• Minimum Dose: The minimum effective dose of vigorous training is once a week, using a protocol like the one minute on, one minute off (repeated 10 times for a 20-minute workout).

If you are 40+ and lifting weights today, conclude your resistance workout with a single 30-second all-out sprint (on a bike or rower) followed by 3 minutes of full rest, and try to repeat this 3–4 times if you can recover fully.

• Mistake: Doing moderate-intensity cardio or classes like Orange Theory/F45 (that keep you in a smashed state).
  Fix: Avoid moderate-intensity work, as it increases cortisol without the beneficial hormonal response needed to dampen stress. Polarize your training toward either very high intensity or very low-intensity recovery.
• Mistake: Using a Tabata protocol (20 seconds on/10 seconds off) for maximum adaptation.
  Fix: Tabata protocols don't allow enough recovery to hit true maximal effort needed for the best changes. Use 2–3 minutes of rest after a maximal effort sprint to ensure quality.
• Mistake: Combining high-intensity cardio (like jogging) with resistance training.
  Fix: If combining, use Sprint Interval Training (SIT) on the same day as heavy lifting, or ensure the cardio is very low-intensity walking for recovery. Too much concurrent cardio can compromise progress.
• Mistake: Focusing on Zone 2 cardio as the primary path to longevity for women 40+.
  Fix: While important, Zone 2 alone is often not the most efficient driver of body composition and hormonal changes needed as estrogen declines. Resistance and high-intensity work are the big rocks that create the epigenetic and metabolic changes necessary.

• “I am so busy that I need a program that is already thought out and all I need to do is hit play and do the work. Any great recommendations? I am 40 yrs old and consider myself to be pretty experienced in resistance training, HIIT and endurance training. Thanks!!”
• “What about 40 seconds on 20 seconds off?” (Suggesting alternative ratio)
• “The more I listen to nutrition and health podcast, the more confusing it becomes.. I hear the opposite for other experts... I’m 56 and I’ve been doing it for years... She’s also spot on with the training. You need to build on those muscles and movement etc.” (Highlighting that training principles are key, despite confusion on other topics.)

For women 40 and older, the longevity training regimen must be polarized and intense. Focus on heavy resistance training (3–4x/week) to preserve muscle mass and induce bone density changes, and complement this with Sprint Interval Training (SIT) 1–2 times per week—using short, all-out bursts followed by generous rest (30 seconds work, 2–3 minutes rest, 4–6 rounds). This specific intensity is the most efficient way to achieve the cardiovascular, metabolic, and neuroprotective benefits needed to combat age-related decline without over-stressing the female hormonal system.