Heart Rate Monitoring INSY 3021 Auburn University Spring 2007
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
Q = HR x SV (L*/min) (beats/min) (L*/beat) *- ml. also commonly used Cardiac Output
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.