Reference

A Plain-Language Glossary of the Terms That Get Thrown Around

What the words mean, without the jargon or the supplement pitch.

Health and fitness language is unusually bad at explaining itself, and a lot of it is used to sell things. Here's what the terms actually mean.

Nutrition and digestion

Microbiome
The community of bacteria and other microbes living in your gut. Its diversity tracks the diversity of plants you eat, and it affects absorption, energy and how comfortable training feels.
Short-chain fatty acids
Compounds your gut bacteria produce when they ferment fiber. They feed the cells lining your gut. This is a large part of why fiber matters.
Fermentable fiber
Fiber your gut bacteria can eat, in beans, onions, some fruit. Good for you, and badly timed if it peaks mid-session.
Polyphenols
Plant compounds in berries, olive oil, cocoa, tea and coffee. Among other things, they feed beneficial gut bacteria.
Gastric emptying
How fast food leaves your stomach. Fat slows it. Useful most of the time, unhelpful in the two hours before hard training.
Blood sugar spike
A sharp rise in blood glucose, usually followed by a dip. The dip is the mid-afternoon fog people blame on their job.

Training

Progressive overload
Gradually increasing demand so tissue adapts. The most common cause of a new niggle is a jump that felt reasonable.
Deload week
A planned week of reduced training so adaptation catches up. Skipping them is how consistent people become unavailable people.
VO2 max
The maximum oxygen your body can use during hard effort. A rough proxy for aerobic fitness, and one of the better predictors of long-term health.
Zone 2
Effort you could sustain while holding a conversation. Boring, and the foundation of endurance.
Training block
A multi-week stretch aimed at one thing. Useful because adaptation happens over weeks, not sessions.
Available to train
Not injured, not run down, not too depleted. Most lost progress is lost here rather than to bad programming.

Recovery and aging

Muscle protein synthesis
The process of building muscle tissue. Becomes less responsive with age, which is why protein distribution matters more later.
Sarcopenia
Age-related loss of muscle mass and strength. Largely responsive to resistance training and adequate protein, common, not inevitable.
Connective tissue
Tendons, ligaments and fascia. Adapts more slowly than muscle, which is why it's usually the thing that complains first.
Sleep debt
Accumulated shortfall against what you need. Compounds, and it degrades recovery, immunity and decision-making together.
RED-S
Relative Energy Deficiency in Sport, the consequences of chronically eating less than training demands. Shows up as flat mood, stalled strength, getting ill and poor recovery, and it's more common in ordinary active adults than most realize.

Coaching

Marker
The single thing you rate weekly for your program. Noise day to day, the clearest signal we have over two months.
Scope of practice
The boundary of what a coach may work on. Coaching covers nutrition, training and lifestyle for adults. Diagnosis and treatment sit with your doctor.

Working on this properly? This is ground we cover in PATH Foundations, with someone looking at your actual week rather than a general guide.

General education for healthy adults. Not medical advice, and not a substitute for your own doctor or provider. Print this page if it's useful, it's formatted for it.

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