Cardiovascular drift

Cardiovascular drift (CVD, CV_drift) is the phenomenon where some cardiovascular responses begin a time-dependent change, or "drift", after around 5–10 minutes of exercise in a warm or neutral environment 32 °C (90 °F)+ without an increase in workload.^[1][2] It is characterized by decreases in mean arterial pressure and stroke volume and a parallel increase in heart rate.^[3] It has been shown that a reduction in stroke volume due to dehydration is almost always due to the increase in internal temperature.^[4] It is influenced by many factors, most notably the ambient temperature, internal temperature, hydration and the amount of muscle tissue activated during exercise.^[2] To promote cooling, blood flow to the skin is increased, resulting in a shift in fluids from blood plasma to the skin tissue.^{[citation needed]} This results in a decrease in pulmonary arterial pressure and reduced stroke volume in the heart.^{[citation needed]} To maintain cardiac output at reduced pressure, the heart rate must be increased.

Effects of cardiovascular drift are mainly focused around a higher rate of perceived effort (RPE); that is, a person will feel like they are expending more energy when they are not.^[1] This creates a mental block that can inhibit performance greatly.^{[citation needed]}

Cardiovascular drift is characterized by a decrease stroke volume and mean arterial pressure during prolonged exercise.^[5]  A reduction in stroke volume is the decline in the volume of blood the heart is circulating, reducing the heart’s cardiac output.^[6] The stroke volume is reduced due to loss of fluids in the body, reducing the volume of blood in the body.^[7] This leads the increase in heart rate to compensate for the reduced cardiac output during exercise.^[6] This inefficient cardiac output leads to a decrease in the maximum amount of oxygen used by the body – VO_2Max.^[8] This affects exercise performance by reducing the amount of oxygen that is delivered to the muscles during exercise.^[8]

Prevention or minimization of cardiovascular drift includes consistently replacing fluids and maintaining electrolyte balance during exercise, acclimatization to the environment in which one is performing, and weight training^{[citation needed]} to supplement cardiovascular efforts. Fluid intake can reduce cardiovascular drift during periods of sustained exercise, but maintains VO2 max levels.^[9] Vascular function and blood pressure can be negatively affected if dehydration occurs.^[10] Short term exercise in extreme heat conditions negatively affects VO2 max levels.^[11] Exercise over a longer period of time allows the body to acclimate, minimizing cardiovascular drift.^[11]