A clinical reference from Vital Capacity

The 7 tests are only the beginning.

ApoB, Lp(a), fasting insulin, OGTT with insulin, VO₂ max, DEXA and grip strength measure different parts of cardiovascular risk, glucose response, fitness, body composition and strength. A result only becomes useful in clinical context.

Download the complete reference free, with no email required. Use it to understand the tests. Then notice the part that still requires a physician on the hook: defending the next clinical decision in their own name.

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A free clinical reference. Vital Capacity is in development and not accepting patients.

Vital Capacity

Clinical Reference

The 7 Tests
Routine Care
Usually Misses

The numbers matter. The physician judgment after the numbers matters more.

Andrew Irwin, MD, CSCS

Internal Medicine | Human Performance

What is inside

Seven measurements, grouped by clinical question.

  1. 01

    Vascular

    ApoB

    Estimates the number of atherogenic particles. It can add information when LDL-C and particle burden are discordant.

    [1]
  2. 02

    Vascular

    Lp(a)

    A genetically influenced cardiovascular risk factor. The 2026 multisociety guideline recommends measuring it at least once in adults.

    [1]
  3. 03

    Metabolic

    Fasting insulin

    Measures insulin concentration in a fasting sample. Assays vary; the value should not be interpreted against a universal threshold.

    [2]
  4. 04

    Metabolic

    OGTT with insulin

    Measures glucose response to an oral challenge. The IDF recognizes 1-hour post-load glucose as useful in people at risk; insulin curves require separate interpretation.

    [3]
  5. 05

    Cardiorespiratory

    VO2 max

    A measure of cardiorespiratory fitness. A large treadmill cohort found an association between fitness and lower long-term mortality; it was observational.

    [4]
  6. 06

    Metabolic

    DEXA body composition

    DXA can report bone mineral, lean and fat mass. Some systems estimate visceral adipose tissue; the estimate depends on the device and method.

    [5]
  7. 07

    Musculoskeletal

    Grip strength

    A simple test associated with all-cause and cardiovascular mortality in a large population cohort. It is a risk marker, not a direct measure of all muscular function.

    [6]

The reference and the responsibility

The reference can show you

What to measure, why the test matters, and what a concerning result may suggest.

A physician still has to decide

Whether to treat, repeat, refer, hold, screen relatives, adjust training, or take responsibility for a prescription.

See four of these tests read together in the composite sample case below.

Sample case · composite for illustration

What the numbers look like with a plan attached.

Four of the seven tests, read together for one composite athlete. The standard is that a patient leaves knowing what is limiting performance and raising future risk, the evidence behind it, the first actions, the retest plan, and the decisions that need follow-up.

The full reasoning behind this case is in the Substack essay The Hidden Ceiling.

Vital Capacity Arc Report

Elite fitness, hidden metabolic risk

Composite

M.K. / 47 / C-suite

VO2 max

58

mL/kg/min

top 5% for age

ApoB

98

mg/dL

above goal

Lp(a)

150

nmol/L

above threshold

Fasting insulin

14

µIU/mL

above target

Primary bottleneck

Cardio is elite. Metabolism isn't keeping up.

Physician recommendation

Start moderate-intensity statin therapy concurrently with lifestyle intervention. Family history, Lp(a), ApoB, and borderline blood pressure make delay the wrong default.

Top actions

  • Eliminate fasted high-intensity sessions.
  • Anchor meals: protein and fiber first.
  • Reduce training volume 15-25% for six weeks.

Retest clock

  • Fasting insulin and glucose at week 8.
  • OGTT with insulin at week 12.
  • ApoB and lipid panel at 3-4 months.

Coordination flags

  • Sports dietitian if adherence stalls.
  • Cardiology trigger if symptoms or CAC shift.
  • Family screening context for inherited risk.

Prepared by Andrew Irwin, MD, CSCS. A composite teaching case, not a real patient, and the intended standard for future Vital Capacity clinical documentation.

Why this exists

The tests are accessible. The interpretation is where people get lost.

The point is not to collect another list of tests. It is to ask which measurements change the clinical question, which results need context, and what should happen next.

01

Plain-language explanations of seven measurements and what each one measures.

02

Targets and thresholds that help you understand when a result deserves attention.

03

A clinical frame for turning numbers into questions worth asking a physician.

04

Questions to take to your physician when a result deserves a closer look.

Sources

References behind the summaries.

These sources support the brief descriptions above. They do not establish a diagnosis or a personal testing plan.

  1. [1]
    2026 ACC/AHA multisociety guideline on dyslipidemia

    Circulation. ApoB and Lp(a) measurement recommendations.

  2. [2]
  3. [3]
  4. [4]
  5. [5]
  6. [6]

About the author

Andrew Irwin, MD, CSCS

Internal medicine physician and Certified Strength and Conditioning Specialist with competitive training experience across Ironman, Hyrox, marathons, rugby, and hockey.

He is building Vital Capacity to connect clinical medicine and exercise physiology in one physician-led practice: labs, fitness, strength, body composition and recovery, read as one picture.

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