Three workout apps on the home screen. Two produce overlapping data. Combined subscription cost: about forty pence a day. Total useful change to training outcomes versus a single free-tier app: zero. The category isn't malicious. The category has a stack-accumulation failure mode that almost every adult trainee falls into and almost nobody names.
Volume 43 continues Tier 7 — the technology layer — with the software side of consumer fitness. Apps for workout logging. Nutrition trackers. Online coaching platforms. AI coaching tools (a genuinely new category since 2022 with a rapidly evolving capability profile in 2026). And the data privacy considerations spanning all of them. The volume specifies what works, what doesn't, and where the same product helps one trainee and harms another.
Inside this one
- The workout app framework — what supplements sustained practice and what fragments it
- Nutrition tracking honest — accuracy limits, food-anxiety pattern, the minimum-effective use case
- AI coaching in 2026 — genuine capability, hallucination risk, scope creep into clinical territory
- Online coaching platforms — qualified-human-mediated versus platform-as-coach, what actually works
- Data privacy — the "free app" business model and the consolidated-profile risk
- The when-to-trust-the-algorithm decision tree
The standard it is held to
Every factual claim in this volume names its source, and every claim carries a confidence grade — settled, strong, emerging or contested. Where the evidence is thin, the text says so. How it’s made, in full → · What we’ve got wrong →