Our approach to science

Cycla is built on exercise science and the current research on hormonal health. Here's what that means in practice - what we build on, what we don't claim, and why your data matters more than any phase label.

Philosophy

The fitness industry has a pattern: take an emerging idea, simplify it into a marketable claim, and build a product around it before the science catches up. "Cycle-syncing" followed that pattern. The core insight is real - hormones influence energy, recovery, and performance. But the leap from "hormones matter" to "your phase determines your workout" skips over a lot of nuance.

Cycla takes a different position. We treat your cycle as context, not command. It's one of several signals - and not the most responsive one. Your daily check-in (energy, sleep, symptoms, mood) is the primary driver of every session adjustment. Your cycle provides hormonal context. Your conditions add depth.

How the algorithm works

Every day, Cycla builds a session from four layers:

• Baseline plan: Your training programme (strength, cardio, mobility) based on your fitness level and goals.
• Daily adjustment: Your check-in modifies intensity, volume, and exercise selection in real time. Low energy? Fewer sets, lighter load. High energy? The plan pushes further.
• Cycle context: Your current phase adds hormonal context. This can shift exercise selection (e.g., pelvic floor work during menstruation) and slightly adjust volume - but it never overrides what your check-in says.
• Condition logic: If you have a condition like PCOS or endometriosis, Cycla applies condition-specific rules. These are grounded in published research: insulin sensitivity training for PCOS, anti-inflammatory sessions during endo flares, bone density work for perimenopause.

Over time, Cycla learns your patterns. By cycle 3, it starts detecting how your body actually responds. By cycle 5, your plan reflects your data, not averages.

What we don't claim

Honesty about uncertainty is part of how we build trust. Here's what the research doesn't yet support strongly enough for us to make definitive claims:

• Phase-specific strength windows: The idea that you're definitively "strongest" during the follicular/ovulatory phase is based on oestrogen's effect on muscle protein synthesis. The evidence is suggestive but not conclusive. Individual variation is large. We use this as context, not prescription.
• Precise hormone-to-performance mapping: Hormone levels vary enormously between people and between cycles. A fixed mapping of "Day 14 = peak power" doesn't hold for most people. That's why your check-in always takes priority.
• Cycle-syncing as a proven training method: There is no large-scale RCT showing that cycle-synced training produces better outcomes than well-programmed training that accounts for daily readiness. We're honest about this.

What the research does support

Where we do build on strong evidence:

• Daily readiness matters: Autoregulation (adjusting training based on daily readiness) consistently outperforms rigid programming in both performance and adherence research.
• Conditions require specific adaptation: PCOS responds well to strength training (insulin sensitivity). Endometriosis benefits from anti-inflammatory movement during flares. Perimenopause requires weight-bearing exercise for bone density. These are well-supported in the literature.
• Hormones influence recovery: Progesterone's catabolic effect, oestrogen's role in tendon health, the impact of menstruation on iron levels - these effects are real and inform our recovery logic.
• Symptom tracking improves outcomes: Regular self-reporting of energy, sleep, and symptoms improves training adherence and reduces injury risk. This is why the daily check-in is our primary signal.

Key references

• McNulty et al. (2020). "The effects of menstrual cycle phase on exercise performance in eumenorrheic women: a systematic review and meta-analysis." Sports Medicine, 50(10), 1813–1827.
• Wikström-Frisén et al. (2017). "Effects on power, strength and lean body mass of menstrual/oral contraceptive cycle based resistance training." Journal of Sports Medicine and Physical Fitness, 57(1-2), 43–52.
• Moran et al. (2011). "Lifestyle changes in women with polycystic ovary syndrome." Cochrane Database of Systematic Reviews.
• Armour et al. (2019). "Exercise and endometriosis: a systematic review." BMC Women's Health, 19(1), 164.
• Berin et al. (2022). "Resistance training for treatment of PCOS." Medicine & Science in Sports & Exercise, 54(8), 1286–1293.
• Stanton & Handy (2022). "Exercising through the menopause transition." British Journal of Sports Medicine.
• Mann et al. (2014). "The APRE: Setting repetitions and load based on performance." Journal of Strength and Conditioning Research.

Our commitment