Exercise Prescription and Rehabilitation Considerations for Older Adults: Summary 72
V02 max increases with exercise training which signifies improvement in aerobic capacity. Heart Rate (HR) With aerobic exercise there is a linear relationship between HR and oxygen consumption (HR increases with increasing workload). Maximum HR is related to one’s age (decreased with aging). With aerobic training, the HR will be lower at rest and during submaximal exercise. After exercise training than an individual can perform more work at a lower HR. Maximum HR will remain stable despite aerobic training and will not be altered. Stroke Volume (SV) SV is the difference between the total amount of blood in the ventricles after completely filling (known as end diastolic volume) and the amount of blood left in the ventricles after ventricular contraction (end-systolic volume). SV increases during aerobic exercise up to intensities of 40-60% of maximum and then it begins to plateau. It is also expressed as ejection fraction, which is a description of stroke volume as a percentage of the end-diastolic volume. SV can be affected by many things including pathologies that reduce ventricular filling or emptying. Cardiac Output (CO) Cardiac Output = HR x SV At rest cardiac output is approximately 5 L/min; with exercise it can increase up to 20-40 L/min. When exercise intensity increases, there is a linear increase in cardiac output. Increases in both stroke volume and heart rate during aerobic exercise are responsible for the increase in cardiac output. In older adults, maximum cardiac output decreases due to decreases in heart rate and stroke volume. Anything that limits heart rate or stroke volume responses during exercise/activity can further limit aerobic capacity. • Examples : deconditioning or bed rest in older adults: will greatly impact cardiac output and aerobic capacity Arterial and Venous Oxygen Content Arterial Oxygen Content : • How much oxygen is present in the arterial blood is determined by the oxygen-carrying capacity of the blood (hemoglobin concentration and red blood cell count impact this) and oxygen loading in the lungs • Oxygen loading in the lungs is well maintained early in aging but in those >85 changes can be seen, including desaturation Venous Oxygen Content : • Oxygen content in the venous systems is determined by oxygen delivery, uptake, and use in the peripheral tissues
INTRODUCTION
AEROBIC CAPACITY AND ENDURANCE
Aerobic Capacity
LEARNING TIP! Impaired aerobic capacity = impaired endurance
• Impaired aerobic capacity limits participation in functional, occupational, and recreational activities • Factors that lead to impaired aerobic capacity in older adults: ○ Anatomic and physiological changes that occur with aging ○ An increase in sedentary lifestyle ○ Greater risk for disease processes that impair oxygen transport • Impaired aerobic capacity in older adults can be due to many factors: ○ Deconditioning : ■ This decrease in activity can be due to illness, functional limitations, cognitive limitations ○ Age-related physiological changes : ■ Reduced maximum oxygen consumption because of decreased cardiac performance and skeletal muscle endurance ○ Pathologies : ■ Parkinson’s disease, osteoarthritis, bone fractures ■ Cardiovascular, pulmonary, and metabolic pathologies – interfere with oxygen delivery and aerobic capacity • Limitations in aerobic capacity are correlated with declining functional mobility, disability, and loss of independence in older adults • Forms of aerobic exercise: ○ High-intensity interval training ○ Walking, treadmill walking ○ Arm ergometry cycling ○ Cycling • Aerobic exercise has been shown to improve cognitive function in older adults: ○ Improvements have been noted in auditory attention, cognitive speed, visual attention, and cognitive flexibility VO2 and VO2Max Aerobic capacity reflects the body’s ability to take up, deliver and use oxygen. Impairment in any part of the oxygen delivery system can affect an individual’s aerobic capacity. Oxygen consumption is referred to as V02. V02 max is directly related to aerobic capacity.
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