6.3 Resting Vital Signs, Body Composition & Resting ECG

Resting Vital Signs, Body Composition & Resting ECG

Quick Answer: Resting measurements establish the baseline against which every exercise test and training session is judged. Heart rate and blood pressure must be measured with standardized technique to be trustworthy; blood pressure is then classified against the 2017 ACC/AHA categories. Body composition and a resting 12-lead ECG round out the baseline picture used for risk stratification and, later, for comparison against exercise-test findings (Chapter 7) and ECG changes (Chapter 4).

Resting Heart Rate

Resting heart rate (RHR) can be measured by radial or brachial palpation for 30–60 seconds, by auscultation, or from a resting ECG tracing. A typical adult resting range is roughly 60–100 beats per minute, though well-trained individuals commonly sit below 60 bpm as a normal training adaptation rather than a pathology. RHR should be measured after the patient has been seated quietly for several minutes, since recent activity, caffeine, anxiety, or talking during measurement will inflate the value and misrepresent the true baseline.

Resting Blood Pressure: Technique Matters as Much as the Number

Inconsistent technique is one of the largest sources of error in clinical blood pressure measurement. Standardized technique includes:

• Patient seated with back supported, feet flat on the floor, legs uncrossed
• Arm supported at heart level, not held up by the patient
• No talking, caffeine, or exercise in the 30 minutes prior
• A properly sized cuff, with the bladder covering about 80% of the arm circumference
• At least 5 minutes of seated rest before the first reading
• Two or more readings, roughly 1 minute apart, averaged

Measuring immediately after the patient walks in without rest, or using an undersized cuff, produces a falsely elevated reading — a frequent source of error in practice and a common exam trap.

2017 ACC/AHA Blood Pressure Categories

A hypertensive-crisis reading requires prompt reassessment and, if confirmed alongside signs of organ damage, immediate medical attention rather than proceeding with testing or exercise.

Height, Weight & BMI

Height and weight yield BMI (kg/m²), classified as underweight (<18.5), normal (18.5–24.9), overweight (25.0–29.9), and obese (≥30.0). BMI is a screening tool, not a diagnostic one — it does not distinguish fat mass from muscle mass, which is why waist circumference and, where available, direct body-composition testing add clinically useful information BMI alone cannot provide.

Waist Circumference

Waist circumference identifies increased cardiometabolic risk independent of BMI, and is particularly useful in patients classified as normal-weight or overweight by BMI (it adds little additional predictive value once BMI reaches roughly 35 kg/m² or higher). The commonly referenced increased-risk cutoffs are greater than 102 cm (40 in) for men and greater than 88 cm (35 in) for women, measured at the level of the iliac crest at the end of a normal exhalation.

Pulse Oximetry (SpO₂)

Resting pulse oximetry (SpO₂) is a standard resting biometric in the clinical exercise setting, particularly for patients with known or suspected pulmonary disease. A typical resting SpO₂ in a healthy adult at sea level is roughly 95–100%; values that trend meaningfully lower at rest, or that drop further with mild exertion, are a signal for closer monitoring and possible supplemental-oxygen assessment during testing and training (developed further in the pulmonary exercise-prescription discussion in Chapter 8). Like heart rate and blood pressure, a resting SpO₂ reading should be interpreted against the patient's own baseline rather than a single population cutoff, since chronic pulmonary disease can shift what is "normal" for a given individual.

Body Composition Assessment Methods

The Resting 12-Lead ECG

A resting 12-lead ECG establishes a baseline rhythm, rate, axis, and waveform pattern before any exercise testing occurs. This baseline is essential context for interpreting exercise-induced changes: an abnormality present at rest, such as a baseline conduction block or an old infarct pattern, must be distinguished from a genuinely new, exercise-induced change. A resting 12-lead is a single point-in-time snapshot; telemetry refers to continuous, wireless ECG monitoring carried through testing and training sessions, used when a patient's risk stratification or known arrhythmia history calls for ongoing rhythm surveillance rather than a single tracing. Chapter 4 covers waveform interpretation, arrhythmias, and ischemic changes in depth; Chapter 7 covers how the resting tracing informs exercise-test lead preparation and monitoring level.