How Much Exercise Do Women 40+ Really Need? Rethinking the 150-minute guideline

Sims frames the 150-minute moderate guideline as harmful for women in perimenopause because it lacks the necessary stimulus to produce adaptation but still increases cortisol. She explains that the shift in estrogen/progesterone ratios leads to diminished receptor sensitivity, gut changes, and a cascade of symptoms (brain fog, vasomotor symptoms, bone loss, lean mass loss). To counteract this, the body needs a stress that triggers adaptations—much like how the hormones used to help. Polarized training, with its super high-intensity efforts, creates such stress. She doesn't provide exact session lengths or frequencies in this excerpt, leaving it as a general recomposition of a woman's weekly exercise pattern. The concept is directly contrasted with the 'abysmal' 150-minute guideline based on 20-year-old science.

Sims emphasizes that what's commonly recommended—10–12 exercises without specifying load, reps, or sets—is insufficient. She separates the goals of muscle size (fatigue-based) from strength/power (heavy-load CNS). For women losing estrogen, the first casualty is contraction strength. She cites recent studies in women aged 70–80 where switching to 5–7 rep heavy loads improved power, lean mass, strength, and fall prevention. The key is that 'heavy' is individual: for a novice, a 30 lb barbell can be heavy. She advises a 3-month movement-learning phase to establish proper mechanics before loading. After that, undulating periodization keeps the stimulus life-long. The advice is not about building for a race but maintaining function from 50 to 100.

Sims is adamant that women who have never lifted should not walk into a gym and try to lift heavy without guidance. The first 3 months should be all about 'phasing in for that proper movement.' She suggests seeking out a movement professional—physio, kinesiologist, or personal trainer—who can give cues and ensure no hip discrepancies or range-of-motion issues. The goal is proper mechanics, not load. Even at this stage, fatigue can be achieved with light loads and perfect form. The phase is about CNS connection and movement quality, which she sees as foundational for the rest of one's life. This is particularly important because many women think 20 air squats qualifies as resistance training, and she wants to shift that mindset.

Sims explains that perimenopause brings a change in the estrogen-to-progesterone ratio, reduced sensitivity of estrogen and progesterone receptors, and shifts in the gut microbiome. These feed forward to body composition changes, brain fog, vasomotor symptoms, accelerated bone mineral density loss, and lean mass loss. Moderate-intensity exercise is not a hard enough stress to produce adaptations, but it is hard enough to spike cortisol. Because women in perimenopause already have elevated baseline cortisol and sympathetic drive, adding this type of exercise further sabotages body composition and metabolic health. Instead of adaptation, you get chronic stress. She frames the 150-minute recommendation as 'exactly the opposite' of what these women should be doing.

Sims makes a sharp distinction: when you train to muscle fatigue (high volume, moderate loads), you are stimulating muscle protein synthesis and lean mass gain. That’s valuable, but it won’t restore the strength and power that plummet when estrogen shifts. Estrogen normally stimulates satellite cells for muscle repair and, critically, influences how strong the muscle contraction can be. With fluctuating and declining estrogen, the nervous system’s ability to recruit motor units and release acetylcholine weakens. Heavy loading—relative to the individual—forces a central nervous system adaption: faster nerve signaling and greater acetylcholine release at the neuromuscular junction, generating a strong contraction regardless of estrogen status. This CNS-derived strength is vital for proprioception, carrying the body through space, and preventing falls. She cites recent studies in women aged 70–80 where switching from traditional 10–12 rep lighter work to 5–7 rep heavy loads increased power, lean mass, strength, and fall prevention. The heavy load must be relative—starting with body weight or a 30 lb barbell—and progressed. The goal is life-long undulating periodization, not short blocks.

Sims explicitly rejects the idea of a 'training block' for this population. Her advice is to adopt undulating periodization—lifting heavy loads some days, bringing the load down other days, then lifting heavy again—and never stopping. The goal is to preserve strength, power, and proprioception from age 50 to 100. This requires a shift in mindset: exercise becomes a permanent, flexible structure that adapts to life, not a plan to peak for an event. She ties this to the same CNS rationale: the heavy load stimulus is needed regularly to maintain nerve signaling strength. Without that constant adaptation, the decline in estrogen-driven muscle contraction strength accelerates. This approach also integrates with the need for movement quality and injury prevention.