The Science Behind our Class Formats

Each of our formats is built around a specific, well-documented theme in Stacey Sims' research and public writing on women's strength training and long-term health — most notably that women are frequently under-trained relative to what the evidence supports, particularly around load intensity, power work, and recovery management. This document reflects Sims' publicly documented research themes and recommendations rather than citations to individual studies, and isn't a substitute for individualized medical or exercise-science guidance.

Power & Foundation

This class exists because strength and power decline at different rates as women age — and most training programs only address one of them. Dr. Stacy Sims' research is explicit that women lose fast-twitch (Type II) muscle fiber and explosive power output faster than they lose raw strength, yet fitness programming for women defaults almost entirely to steady-state cardio or light, high-rep work that never trains power directly. Power & Foundation dedicates a distinct block to true power work — heavy kettlebell swings and high pulls performed with full recovery between sets, prioritizing speed and force output over volume — paired with controlled, heavy-resistance Microformer work for foundational strength. Power output is a stronger predictor of functional capacity and fall resistance in older adults than strength alone, which is why this class treats power training as a non-negotiable component rather than a warm-up formality.

Posterior Chain & Bone Density

Bone remodels in direct response to mechanical stress, and heavy hip-hinge loading — deadlift patterns in particular — is among the most effective, well-supported stimuli for maintaining bone mineral density. This matters more for women than for men, given the accelerated bone loss that follows the drop in estrogen around menopause. Sims argues that women are routinely under-loaded in typical programming, coached toward moderate weights when the evidence supports genuinely heavy resistance training as protective for the skeleton. This class is built entirely around that principle: heavy single-leg RDLs, hip hinge pulls on the Microformer, and loaded carries, all working the same posterior-chain and hip-loading patterns that the bone density research points to as most protective.

Upper Body Power & Grip Strength

Grip strength is one of the more consistently replicated predictors of long-term health and functional independence in aging research — it's used as a simple proxy for overall strength and resilience precisely because it correlates so strongly with broader health outcomes. Despite this, women's strength programming is disproportionately lower-body focused, leaving upper-body bone loading (through the wrists, forearms, and shoulders) and grip capacity undertrained. This class corrects for that gap directly: heavy presses, rows, and loaded carries with a deliberate grip-strength emphasis, building the upper-body strength and bone loading that's just as relevant to long-term function as anything trained in the lower body.

Metabolic Power Intervals

Sims' research pushes back on the assumption that more steady-state cardio is always better for women's metabolic and hormonal health. Chronic, moderate-intensity endurance work can act as an ongoing stressor without delivering a proportional benefit, particularly for body composition and metabolic markers in women. Her recommendation instead favors short, genuinely intense efforts followed by real recovery — go hard, then rest, rather than sustaining moderate effort for long periods. This class is built on that exact structure: a heavy power block followed by 40-second-on, 20-second-off intervals across four rounds, designed to deliver a strong metabolic stimulus in 45 minutes without the chronic-stress cost of an hour of steady cardio.

Total-Body Heavy

If there's one message that runs through Sims' work most consistently, it's this: women should lift heavy things. Conventional advice has long steered women toward light weights and high reps, but the evidence Sims cites points the other way — heavy, low-rep resistance training across major compound patterns is what actually preserves lean muscle mass, supports metabolic rate, and builds functional strength as women age. This class is the most direct expression of that principle: squat, hinge, push, and pull, each trained at the heaviest manageable load across both the Microformer and kettlebells, with low rep counts and full recovery between sets, rather than pursuing high-volume fatigue for its own sake.

Hip Stability & Injury Prevention

Fall-related fractures are one of the leading drivers of serious injury and loss of independence in older women, and the research is clear that single-leg strength and balance capacity are protective factors that need to be built well before that risk becomes relevant. This class trains unilateral strength and balance directly — single-leg deadlifts, lateral step patterns, and anti-rotation core work — rather than treating stability as a byproduct of general strength training. Sims' framing is that this kind of training is preventative, not corrective: the earlier it's built into a woman's training history, the more protection it offers decades later.

Hormonal Recovery & Resilience

Sims writes specifically about perimenopause as a period requiring adjusted — not reduced — training. Fluctuating estrogen affects recovery capacity, cortisol regulation, and connective tissue resilience, which means the same training stimulus can take longer to recover from during this stage of life. Her guidance is explicit that under-training during perimenopause is a mistake, since this is precisely when women need to be protecting against accelerating muscle and bone loss — but total volume and stress load do need to be managed alongside that continued heavy work. This class reflects that balance directly: the same heavy-loading standard as the rest of the program, with fewer total sets, more built-in rest, and an extended, breath-focused close designed to support nervous-system recovery rather than add to the day's overall stress load.