Physical Activity and Wellness: Lifespan, Health Span, and Fitness Components

Health Span, Lifespan, and Physical Wellness

• Health Span vs. Lifespan: While drastic lifespan extension may not always be the goal, physical activity can change the shape of the life curve. This means spending many more years in greater health, living later years (70s, 80s, 90s) with a high degree of health, not bedridden or low energy, and able to engage in activities like playing with children or grandchildren. This enhances not only a longer life but also a higher quality of life and a greater health span.

Why Physical Activity?

• Longevity (Quantity of Life) Benefits:

  • Decreased Likelihood of Cardiovascular Disease: "Cardio" pertains to the heart; "vascular" to arteries and veins, the intricate system delivering blood. Increased exercise trains the heart, making it more efficient at pumping and circulating blood. It also makes the vascular system more efficient at diffusing blood and nutrients. This results in a healthier system less prone to cardiovascular diseases.
  • Type 2 Diabetes Remission: Type 1 diabetes is typically genetic and not influenced by exercise. However, Type 2 diabetes is more tied to behavior and can often be put into remission or managed through regular exercise. Exercise is a main way to combat Type 2 diabetes due to its reversibility.
  • Decreased Likelihood of Cancer Diagnosis: Generally, exercise can reduce the likelihood of most types of cancer. While this is a broad statement with specific cancer types being outliers not affected by behavioral decisions, the vast majority of common cancers see reduced risk with physical activity.
  • Reduced Metabolic Syndrome Risk: Metabolic syndrome is defined as a combination of three or more of the following:
    • Abdominal obesity
    • High serum triglycerides (lots of fat in the blood)
    • Low HDL cholesterol (good cholesterol) and high LDL cholesterol (bad cholesterol)
    • High blood pressure
    • High blood sugar
      These conditions often occur in unison and can be drastically reduced or have better outcomes with increased and regimented exercise.

• Quality of Life Benefits:

  • Improved Cognitive Function: Exercise directly benefits brain health and mental sharpness.
  • Better Mental Health Outcomes: Physical activity is known to positively impact mood and reduce symptoms of depression and anxiety.
  • Reduced Stress Levels: Exercise serves as a potent stress reliever.
  • Improved Sleep Outcomes: While exercise generally improves sleep, the timing can matter. Exercising earlier in the day is preferred for sleep improvement, whereas exercising an hour or $30$ minutes before bed may negatively impact sleep quality.
  • Increased Overall Energy (Chronic Effect): While an intense, acute bout of exercise can temporarily drain energy, engaging in long-term exercise programs leads to a substantial increase in baseline, self-reported energy levels throughout the day. This is a chronic, zoomed-out effect.

Components of Physical Fitness

There are five constituent parts of physical fitness:

1. Body Composition:

   • Definition: The ratio of fat mass to lean mass. Lean mass includes any body tissue that isn't adipose tissue (fat), such as skin, blood, organs, and muscle.
   • Quantifying Body Composition:
     • Body Mass Index (BMI): Calculated based on weight versus height. It is fairly accurate for a large percentage of the population but loses accuracy for well-trained athletes or individuals with very high muscle mass, as it doesn't differentiate between fat and muscle. High muscle mass can lead to misclassification as overweight or obese, despite positive health outcomes.
     • Waist-to-Hip Ratio: A simple yet surprisingly accurate measure. More abdominal fat drastically skews the ratio. A lower waist measurement relative to the hip indicates a leaner individual with more lean mass.
     • DEXA (Dual-Energy X-ray Absorptiometry) Scan: The gold standard for body composition readings, used in literature and medical fields. It's a very expensive machine ($40,000$ to $250,000$) that provides detailed information on muscle quantity, distribution (even down to individual limbs or muscle groups), and bone density (useful for assessing osteoporosis risk). You lie on a bed, and an X-ray machine scans your body.
     • Bod Pod: Less specific than DEXA but widely used in research. You sit in an egg-shaped chamber, and air displacement is used to calculate fat mass and lean mass based on height, weight, and dispersed air.
     • Fat Calipers: The cheapest ($20$) and most accessible method. A clinician pinches fat from various body points (three, five, seven, or eleven measurements for increased accuracy), and the readings are entered into a calculator. Its accuracy is highly dependent on the experience and skill of the person administering the test.
   • Trends:
     • Gender Differences: Females typically carry a higher percentage of fat relative to lean mass, due to hormonal reasons and childbirth.
     • Age-Related Changes: Across the lifespan, from early years through adulthood and into senior life, there is a constant tendency for an increase in fat mass and a decrease in lean mass. Body composition shifts from more lean mass/less fat to more fat mass/less lean mass over time.

2. Cardiorespiratory Endurance:

   • Definition: Prolonged exercise that elevates heart rate and respiration, such as jogging, walking, cycling, or swimming.
   • Physiological Benefits:
     • Heart Efficiency: The heart, being a muscle, becomes more efficient with training. It leads to more forceful contractions, pumping more blood per beat, thus requiring fewer beats overall. This is why well-trained endurance athletes often have resting heart rates in the $30s$ or $40s$.
     • Lung Efficiency: Lungs become more efficient at taking in atmospheric air, diffusing it into the blood, and circulating it throughout the body.
   • Other Benefits: Boosts energy and reduces stress, and generally leads to better outcomes across the board compared to other exercise types in many studies.
   • Research Bias: Cardiorespiratory exercise is much easier to research (e.g., on a treadmill) compared to resistance training, leading to more documented benefits in empirical studies due to greater ease of quantification and measurement.

3. Flexibility:

   • Definition: The ability to move through the full range of motion that your body is supposed to have at each joint.
   • Importance: Often neglected but crucial for preventing injuries during other exercise forms. Moving through a full range of motion with resistance also leads to greater muscular hypertrophy (muscle building).
   • Specificity: Flexibility training should be specific to individual goals. Static (holding stretches) vs. dynamic (active movement) stretching can have different impacts and suitability, with some trainers advising caution with static holds due to potential injury risk.

4. Muscular Strength:

   • Definition: Achieved through high-intensity resistance training, typically in the range of $1$ to $5$ repetitions per set. These repetitions should be close to muscular or mechanical failure. Muscular strength exercise usually involves external loads (barbells, dumbbells, kettlebells), though some bodyweight exercises can also contribute.

5. Muscular Endurance:

   • Definition: Achieved through resistance training with higher repetitions, typically $10$ to $30$ or even more, approaching muscular or mechanical failure. Often involves bodyweight or light external loads. All resistance training exists on a continuum between strength and endurance, and rep ranges manipulate which priority is emphasized.
   • Importance in Later Life (Post-$30s$): The benefits of muscular strength and endurance become increasingly critical with age.
     • Combating Sarcopenia: This is the scientific term for muscular loss. After approximately $35$ years of age, everyone experiences a gradual decline in overall muscle mass. Resistance training cannot fully stop this, but it can significantly slow the decline, leading to more muscle at older ages and promoting a longer health span and lifespan.
     • Combating Osteoporosis: This refers to the loss of bone density and mineralization. Similar to muscle loss, bone density tends to increase through early development, peak around $35$ years of age, and then gradually decline, leading to weakened bones. Resistance training helps to slow this bone loss, similar to its effect on sarcopenia.

Exercise Principles

• Specificity:

  • Definition: Ensuring your exercise aligns with your desired outcomes (e.g., training for a marathon would involve more cardiorespiratory work).
  • Personal Application: It is crucial to tie exercise to activities you genuinely enjoy to ensure adherence. For example, if you dislike running, seek other forms of cardio like playing soccer or basketball.

• Progressive Overload:

  • Definition: The body adapts to a given stimulus. To continue seeing adaptations (e.g., getting stronger, increasing endurance), the stimulus must be progressively and incrementally increased over time.
  • Cardiorespiratory Example: The heart and lungs adapt to running, becoming more efficient. To improve further, one must run longer, faster, or with more intensity.
  • Resistance Training Example: Muscles adapt to lifting weights. The nervous system becomes more efficient at activating muscles, and the muscles grow larger and stronger. To continue progress, one must lift heavier weights, do more reps, or increase volume.

• Rest and Recovery:

  • Variability: Rest and recovery needs are highly individual and subjective. Factors include sleep quality, nutrition, training load, and genetic response to training volume.
  • Goal: The aim is to increase training sufficiently to stimulate adaptation but not exceed a threshold that leads to physical burnout. Individual needs for rest must be identified and met.

• FITT Principle (Frequency, Intensity, Type, Time): These four variables can be manipulated to achieve progressive overload or adapt training for specific events.

  • Frequency: How many times per week one engages in physical activity (e.g., weightlifting three times a week, running once a week).
  • Intensity: This is quantified differently for different exercise types:
    • Cardiorespiratory Training: Measured as a percentage of maximum heart rate ($HR<em>{max}$). For instance, if a person's $HR</em>{max}$ is $200$ bpm and their heart rate during a jog is $150$ bpm, their intensity is $75\%$ of $HR_{max}$. Small fluctuations in heart rate directly indicate intensity.
    • Muscular Strength and Endurance Training: Measured as a percentage of a person's one-rep max ($1 \, RM$). Heart rate is too erratic during resistance training to be a reliable measure of intensity. For example, if someone's $1 \, RM$ for a squat is $200$ lbs, and they lift $100$ lbs, they are working at $50\%$ of their $1 \, RM$. This provides a measurable, consistent indicator of intensity.
  • Type: What specific exercises are being performed (e.g., running, hamstring stretches, bench press, jumping jacks).
  • Time: Also differentiated by exercise type:
    • Cardiorespiratory Training: Measured in minutes and seconds (e.g., a $22$-minute, $47$-second swim).
    • Muscular Strength and Endurance Training: Measured in sets and repetitions (e.g., $4$ sets of $15$ repetitions). This provides a more accurate insight into the time under tension for the muscles, rather than overall elapsed time.

Total Daily Energy Expenditure (TDEE)

• Concept: TDEE represents the total number of calories your body burns in a day through all activities, balancing calories in (food/drinks) versus calories out.
• Example: For an individual burning and consuming $3,000$ calories per day (maintaining weight), the expenditure breaks down as follows:
  • Basal Metabolic Rate (BMR): Accounts for approximately $70\%$ of total calories ($2,100$ calories in the $3,000$-calorie example). This is the energy your body uses just to exist—lying in bed, not moving, maintaining internal bodily systems (e.g., breathing, circulation, cell function).
  • Non-Exercise Activity Thermogenesis (NEAT): Accounts for about $15\%$ of total calories. This includes all activities that are not resting or structured exercise, such as walking, sitting, fidgeting, talking, and pacing. It's the energy burned through daily movements.
  • Thermic Effect of Food (TEF): Accounts for about $10\%$ of total calories ($300$ calories in the $3,000$-calorie example). This is the energy required by the body to digest, absorb, and process food. Eating a large meal causes an internal warming effect as energy is expended.
  • Exercise Activity Thermogenesis (EAT): Accounts for only about $5\%$ of total calories. This is the energy burned during structured physical activity like going to the gym, running, or playing sports. While it can increase to $6.5\%$ or even $10\%$ for individuals engaging in hours of intense exercise daily, it generally constitutes a small portion of TDEE. This highlights that while important, structured exercise burns fewer calories than often perceived in the grand scheme of daily energy balance; the majority of calories are burned simply by existing.