Cardiorespiratory Endurance (CRE)

Cardiorespiratory Endurance (CRE)

• Cardiorespiratory endurance (CRE) relies on maximum oxygen consumption or VO2 max, which is the maximum rate of oxygen used by the body during exercise.
• Oxygen Consumption (VO2) measures the rate of total body oxygen consumption each minute.
• Fick Equation calculates VO2 as Cardiac Output (CO) x (A-V)O2. CO often equals 15 L/min, while (A-V)O2 generally equals 0.1.
• Heart Rate is measured as ventricular beats or contractions per minute (bpm).
• Stroke Volume measures the volume of blood ejected per heartbeat, typically in milliliters per beat.
• Cardiac Output (HRxSV) is calculated as Heart Rate x Stroke Volume, and indicates the rate of total body circulation per minute (Liters/min).
• (A-V) O2 Diff refers to the rate of total body oxygen consumption per minute.
• Systolic blood pressure occurs when the heart pumps blood. Diastolic blood pressure represents the pressure pushing against artery walls as the heart rests.
• MET refers to the Metabolic Equivalent of Task. 1 MET equals 3.5ml/kg.
• Target Heart Rate = 220-age.
• Heart Rate Reserve (Karvonen Equation) = Max Heart Rate (MHR) - Resting Heart Rate.
• Target Heart Rate Range using the Karvonen equation: (HRR x 0.5) + RHR or (HRR x 0.85) + RHR

Exercise Effects on CRE

• During exercise, heart rate increases linearly to maximum.
• Stroke volume plateaus at 50% of maximum effort.
• Cardiac output increases linearly to maximum.
• Long-term exercise does not change maximum heart rate.
• Sub-maximum heart rate decreases with long-term exercise.
• Maximum and sub-maximum stroke volume increase with long-term exercise.
• VO2 max increases with long-term exercise.

CRE Measurement and Training

• The maximal treadmill test is used to measure CRE.
• Ambulatory exercises such as walking or running are recommended for weight control, VO2 max improvements, and bone mass.
• Non-ambulatory exercises such as biking or rowing are better for starting exercise, especially for individuals with injuries or joint problems.
• CRE training reduces the risk of chronic diseases, improves cellular metabolism, regulates weight and body fat and also reduces mortality risk.
• ACSM guidelines for CRE training include exercising 3-5 days a week, with an intensity of 55-90% of maximum heart rate, for 20-60 minutes.
• CRE activities include walking, jogging, swimming, and cross country skiing.

Circulation and Electrical Conduction

• The right side of heart pumps deoxygenated blood to the lungs.
• The left side of the heart pumps oxygenated blood to the body.
• Electrical conduction follows this the sequence: SA node, AV node, Bundle of His, Purkinje fibers.

Muscle Strength, Endurance and Flexibility

• Basic muscle structure includes sarcomeres, actin, myosin, myofibrils, and fiber bundles.
• Strength is the capacity to exert maximal force in a single effort, measured by a one-rep max.
• Endurance is the capacity to sustain a contraction or repeat multiple contractions. Maximal repetitions, such as push-ups, assess muscle endurance.
• Flexibility is the ability of a joint to move through its full range of motion (ROM).
• Hypertrophy is increasing the size of muscle.
• Hyperplasia is increasing the number of cells.
• Isotonic contraction is a muscle contraction in which the muscle length changes.
  • Concentric contraction involves the muscle producing tension and shortening, such as the upward phase of a bicep curl.
  • Eccentric contraction involves the muscle lengthening, such as the downward phase of a bicep curl.
• Isometric contraction: The muscle stays the same length, such as holding the weight still.
• DOMS: Delayed Onset Muscle Soreness
• Agonist muscles are the prime movers and contract during exercise.
• Antagonist muscles relax and lengthen during exercise.
• Static stretching involves slowly stretching a muscle and holding the position.
• Ballistic stretching involves suddenly stretching a muscle through bouncing or swinging movements. Due to the activation of the stretch reflex,.
• Proprioceptive Neuromuscular Facilitation (PNF) involves contracting a muscle before stretching it. The contraction stimulates the Golgi Tendon Organ (GTO) to promote relaxation.
• Stretch reflex is activated when muscle receptors send a message to the spinal cord, which then returns a signal telling the muscle to contract.
• Golgi tendon organs (GTO) produce an opposite reflex that causes the muscle to relax when a strong muscle contraction stimulates other tendons.

Aging, Training, and Measurement

• Strength declines by 1% per year after age 35; and declines greater after age 60.
• With age, there is a selective loss of fast-twitch fibers.
• Slow-twitch fibers are maintained with age.
• Muscle endurance is maintained more than strength with age.
• Muscular strength is measured by a one-rep max.
• Muscular endurance is measured with endurance tests like a maximum number of push-ups.
• Flexibility is measured by a sit and reach test.

Physiological Determinants

• Muscle mass is related to cross-sectional area.
• Neuromuscular coordination relates to recruitment of muscle.
• Number of fast twitch versus slow twitch fibres
• Biomechanical leverage relates to the position of muscle attachment around joints.
• Number of slow twitch fibers influences muscle endurance.
• Muscle capillary and mitochondrial density
• Muscle strength
• Neuromuscular coordination/ efficiency

FITT Principle for Strength/Endurance

• 2-3 days/week per muscle group
• Intensity should be 75% 1 RM for strength versus 40-60% 1 RM for endurance.
• Perform 1-3 sets of 8-12 reps for strength or 12+ reps for endurance.
• Multi-joint exercises such as squats and lunges should be performed.

Stretching

• Stretch 2-3 days/week (daily is ideal).
• Stretch to the point of slight tension.
• Hold stretches for 10-30 seconds.
• Stretching types include static, dynamic, or PNF.

Health Relationships

• Benefits of muscle strength, endurance and flexibility include reduced injury risk, improved posture, and lower back pain.
• Developing muscular strength prevents chronic diseases such as CVD (cardiovascular disease) and diabetes.
• Risks include low body fat, which can lead to reproductive/immune issues, and high body fat, which can lead to CVD, diabetes, and metabolic syndrome.