Why High Intensity Training Works Better Than Zone 2 for Women in Perimenopause

Sims emphasizes that most women confuse feeling breathless with true high‑intensity work. The key is polarization within the session: go hard enough to maintain 80–85% HR max during the interval, then use recovery to bring the heart rate down sufficiently to repeat that effort. At the end of the workout, metrics should show that you spent roughly 18–10 minutes in the target zone, not a continuous grind. This protocol directly addresses the perimenopausal drift toward mitochondrial dysfunction and central adiposity, and it also provides a post‑exercise hormonal cascade that counters the cortisol spike many fear. It is not about suffering for long periods; it is about strategic, repeated exposure to a threshold stimulus with built‑in recovery.

Sprint interval training is a subset of HIIT, but it works through a different pathway. The 30‑second all‑out effort, with long recoveries that allow full nervous‑system recoup, creates an extreme metabolic demand that sends a potent signal to reduce visceral adipose tissue and to sensitize cells to insulin via epigenetic modifications. Sims teaches this on the assault bike, where people learn to push as hard as they can and then try to beat their own meter count in subsequent rounds, making it a personal challenge. Because it is so brief and intense, it is often appended to the end of a strength workout, allowing two of the three weekly high‑intensity stimuli to be completed in a single gym visit. The discomfort is a feature, not a bug—it forces a deep systemic adaptation that moderate work cannot match.

Sims frequently uses this template: a morning heavy strength block of front squats or hip thrusts that took 25 minutes, then a sprint finisher on the assault bike or with battle ropes. This approach not only saves time but also retrains women away from the belief that an effective workout must be long. By doing the sprint work after lifting, the body is already warm and neurally primed, and the hormonal environment (testosterone, GH) from the heavy lifting can potentiate the sprint response. She notes that many women are doing 90‑minute sessions that drive cortisol up without the same benefit, and that shortening the gym visit to a focused, combined stimulus is both more effective and less stressful.

Sims contrasts this format with the typical gym prescription of 4 sets of 10 with 90‑second rest, which she believes places women in a stressed state that increases cortisol without proportional benefit. Heavy, low‑rep training stimulates the nervous system and musculoskeletal system powerfully, but because the total volume and time under tension are low, the session does not leave the body in a prolonged sympathetic state. She observes that women who adopt this approach often report feeling energized rather than depleted, and they see strength gains within weeks. This method also pairs well with sprint finishers because the body is primed but not exhausted. The psychological reframe—away from ‘more is better’ and toward ‘heavy and brief’—is a core part of the coaching process.

Sims lays out this schedule as a practical example after explaining that most women need to unlearn the idea that they must exercise every day for an hour. The Monday‑Wednesday‑Thursday split spaces the heavy strength days well, and by finishing one or two of those with a sprint stimulus, you cover two of the three weekly high‑intensity workouts without extra trips to the gym. The additional HIIT day can be built into a walk with friends by sprinting up a hill or stairs for 1‑minute intervals. This template is deliberately flexible and meant to teach women that quality trumps quantity, and that if they listen to their readiness on any given day, they can avoid the moderate‑intensity trap entirely.

Sims frames this practice as a cornerstone of the mind‑body pillar that runs alongside sleep, physical training, and nutrition. She personally does it first thing to guarantee silence. The 10 minutes are not about meditation in the formal sense, but about conscious, quiet awareness—mobilizing, breathing, and observing the environment—which lowers sympathetic output and teaches the skill of shifting into a parasympathetic state at will. For women doing true HIIT and heavy lifting, this reset is essential to prevent the chronic sympathetic dominance that sabotages results. It’s a practical, non‑intimidating entry point into mind‑body work that doesn't require a yoga class or an app.

Sims sees this as one of the hardest lessons for her clients to learn. The cultural conditioning to ‘finish what you start’ and to equate sweat with effectiveness leads women to continue a workout even when they cannot hit the required intensity. But the physiological consequence is a fall into moderate intensity, which generates chronic sympathetic stress with none of the post‑exercise recovery hormones that true high intensity provides. Calling it off and doing something restorative instead is a deliberate act of self‑coaching that reinforces quality over volume and protects the nervous system.

Sims places sleep at the very top of her four‑pillar sequence because she has observed clinically that no amount of exercise or nutritional fine‑tuning compensates for chronic sleep debt. In perimenopause, sleep is often disrupted by night sweats and hormonal fluctuations, making it a critical leverage point. She insists that women work on sleep hygiene and, if necessary, seek medical support before expecting body composition or cognitive improvements from training. This sequencing is counter to many programs that jump directly to diet and workouts, but Sims argues that sleep is the gateway that allows the other pillars to work.

Sims’ sequencing is based on two decades of coaching women through perimenopause. She noticed that when exercise and nutrition are thrown at someone simultaneously, it often fails because both require significant cognitive and emotional bandwidth. Sleep first allows the nervous system to be receptive. Then, heavy lifting and intensity produce tangible strength and body‑composition changes within weeks, which dramatically improves motivation. Nutrition is the hardest piece because many women have built an identity around a specific way of eating (keto, intermittent fasting, vegan, etc.), and challenging that can feel like a personal attack. By delaying nutrition work until trust and physical results are established, Sims finds women are more open to experimentation. Mind‑body techniques, such as the 10‑minute silent morning practice, are introduced early and sustained to teach the nervous system to down‑regulate, which amplifies the benefits of the other three pillars.

Sims explains that in perimenopause, mitochondria begin to dysfunction, muscle quality declines, and visceral fat increases alongside brain fog. When you rely on Zone 2, the stimulus is too weak to provoke the mitochondrial biogenesis and muscle remodeling needed. Women are already efficient at fat oxidation, so spending time there yields no further adaptation. Instead, high‑intensity interval training (HIIT) around 80–85% HR max pulls more fat into mitochondria and improves mitochondrial function, while sprint interval training (SIT) triggers epigenetic changes that reduce visceral fat storage and increase insulin sensitivity. Both modalities also generate a post‑exercise hormonal response (growth hormone and testosterone) that promotes parasympathetic recovery—something Zone 2 does not provide. The key is polarization: workouts must contain truly hard intervals with adequate recovery; falling into moderate intensity (like most group fitness classes) only raises baseline sympathetic drive without the beneficial post‑exercise response, leaving women stuck despite doing ‘all the things.’

Sims notes that true HIIT demands intervals where heart rate hits 80–85% of max and stays there for 1–4 minutes, with variable recovery that allows the body to repeatedly return to that intensity. In contrast, typical group classes use work‑to‑rest ratios that keep participants in a moderate range—hard enough to feel strenuous, but not hard enough to trigger the post‑exercise release of growth hormone and testosterone or the mitochondrial improvements. The result is a persistent sympathetic nervous system activation without the counterbalancing recovery hormones. This leaves women in a chronically stressed state with no body composition or cognitive benefits. The solution is to cut volume and focus on two to three truly polarized sessions per week; if you can’t hit the required intensity on a given day, you stop and do mobility or a slow walk instead of pushing through in the moderate zone.

Sims describes her own workout that morning: front squats and hip thrusts completed in 25 minutes, using 5‑rep sets with full recovery every 2 minutes—no supersets, no extra volume. She argues that heavy loads with low reps leave you feeling ‘worked but not exhausted,’ which promotes a post‑exercise parasympathetic response driven by growth hormone and testosterone release. In contrast, higher‑rep metabolic stress (like 4 sets of 10 with short rest) leaves the body in a prolonged sympathetic state. She periodises strength across three days—Monday squat focus, Wednesday push‑pull, Thursday posterior chain—and often finishes one or two of those sessions with 15 minutes of sprint interval work (battle ropes, kettlebell swings) to compound the stimulus while staying under an hour total. This approach retrains women away from the calorie‑centered, long‑duration mindset and toward quality and recovery.

Sims differentiates sprint interval training (SIT) as 30 seconds or less of all‑out effort followed by 2–5 minutes of full recovery. This format, which she teaches on the assault bike, is intentionally and unavoidably uncomfortable—‘nobody loves it’—but it creates a powerful whole‑body signal that tells the body not to store visceral fat and to become more insulin sensitive. The mechanism involves epigenetic changes that alter gene expression related to metabolism, leading to measurable improvements in body composition without the need for long duration work. Sims recommends two to three high‑intensity sessions per week, often mixing one true HIIT session with two SIT sessions, or vice versa, to cover both mitochondrial enhancement and the visceral‑fat/insulin‑sensitivity axis. The short duration of each SIT workout (15–20 minutes total) makes it compatible with the end of a strength session.

Sims has found over 20 years of coaching that sleep is the non‑negotiable foundation; without it, no body composition or cognitive improvement is possible. She then introduces physical training—heavy lifting and high‑intensity work—because women can see definitive changes in strength and muscle tone within a few weeks, which builds confidence and compliance. Nutrition is addressed afterward because it is ‘so polarizing’—many women identify strongly with a dietary label (keto, IF, vegan, plant‑based) and need trust in the process before they are willing to unpack those beliefs. Mind‑body work, such as a daily 10‑minute silent parasympathetic reset, is taught from the beginning and continues throughout, tying the other pillars together. This sequence reduces overwhelm and leverages early physical wins to open the door for deeper nutritional and lifestyle shifts.