Heart Rate Monitoring

INSY 3021

Auburn UniversitySpring 2007

Functioning

Blood Pressure

Pressure = Blood Flow (Q) x Resistance (P)

Controlling Factors (For Arterial Pressure) Pumping Action of Heart Blood Volume Elasticity of Arterial Walls Blood Viscosity Peripheral Resistance

Cardiac Output

Q = HR x SV(L*/min) (beats/min) (L*/beat)*- ml. also commonly used

Stroke Volume (SV)

SV = Quantity of blood pumped with each beat of the heart (ml/beat)

Factors affecting SV Venous return to heart Distensibility of ventricles Force of contraction of the ventricles in

relation to the pressure in the artery (Aorta or Pulmonary artery)

Sympathetic and hormonal stimulation

Heart Rate (HR)

HR = Heart Beats/min Most commonly studied circulatory

parameter Factors affecting HR

Sympathetic and parasympathetic stimulation of sino-artial (SA) node of the heart

Hormonal stimulation Temperature Age

Task Design and Analysis

What is the maximum load that must be supported?

Design within the acceptable limits of safety!

Estimator- HR Tests

Concept: Estimate MAC from simple tests How accomplished

Have person perform 1 or 2 standard workloads (usually step tests)

Measure HR response Compare results to known values for the

workloads Comments

Simple to perform- little stress Not exact- Good for screening Not as much equipment is required

Assessment of Task Strain

Percent Work Capacity Heart Rate (HR) Analysis

HR Analysis

Maximum HR (ACSM) = 220 – Age

Heart Strain = (Task HR / 220–Age) x 100% (Note: Should be < 65%)

Heart Strain = (Task HR – Resting

HR) / (220–Age–Resting HR) x 100% (Note: Should be < 50%)

Ability to Work Long Durations

Workers will “self pace” at 33 to 44% of VO2 Max for 8 hour shifts

Common task and design criteria is 33% of VO2 Max with HR of 105-115 Beats/min

Work-Rest Cycles

Work–Rest Cycles

Heart rate for a lifting task with 2 minute rest periods.

Must be able to determine if this type of job is acceptable and for whom.

Questions & Comments