Physical Activity: AS 2 Diet, Lifestyle and Health

Welcome to your study guide for Physical Activity! This topic is a core component of Unit AS 2 (Diet, Lifestyle and Health) in CCEA A Level Nutrition and Food Science. In your exam, you will encounter short-answer questions in Section A and potential extended response questions in Section B.

To score top marks, examiners are not just looking for general advice like "exercise more." They want to see precise definitions, exact UK Chief Medical Officers' (CMO) guidelines, and a scientific understanding of how physical activity helps prevent specific diet-related disorders. Let's break this down step-by-step!


1. Key Definitions & The Science of Energy Expenditure

Before looking at recommendations, you need to understand the official terms and how energy expenditure is measured.

• Physical Activity: Any bodily movement produced by skeletal muscles that requires energy expenditure.
• Sedentary Behaviour: Low-energy-expenditure activities (\(\le 1.5\text{ METs}\)) performed while sitting, reclining, or lying down during waking hours. (Note: Sleeping is not considered sedentary behaviour in this context).

What is a MET (Metabolic Equivalent of Task)?

A MET is the ratio of the work metabolic rate to the resting metabolic rate. It helps us compare the energy cost of different activities against resting quietly.

• Definition: \(1\text{ MET}\) is defined as \(1\text{ kcal/kg/hour}\) (roughly the energy used when sitting quietly).
• Sedentary Intensity: \(\le 1.5\text{ METs}\) (e.g., sitting watching television or working at a desk).
• Moderate Intensity: \(3\text{ to } 6\text{ METs}\) (e.g., brisk walking, cycling on level ground).
• Vigorous Intensity: \(> 6\text{ METs}\) (e.g., running, playing competitive football).

Memory Trick: The "Talk Test" for Intensity:
• Moderate-intensity activity: You can talk, but you cannot sing a song without losing breath.
• Vigorous-intensity activity: You can only say a few words at a time before pausing for breath.

Key Takeaway: Physical activity requires skeletal muscle movement and energy expenditure. Activity intensities are classified using METs: Sedentary (\(\le 1.5\text{ METs}\)), Moderate (\(3\text{--}6\text{ METs}\)), and Vigorous (\(> 6\text{ METs}\)).


2. UK Chief Medical Officers' (CMO) Physical Activity Guidelines

CCEA examiners frequently test your knowledge of specific thresholds across different age groups. Memorising these exact figures will secure easy marks!

A. Children and Young People (5–18 years)

• Daily Target: At least 60 minutes of moderate-to-vigorous intensity physical activity every day across the week.
• Activity Types: Engage in a variety of types and intensities to develop movement skills, muscular fitness, and bone strength.
• Sedentary Time: Aim to minimise time spent sitting or being sedentary for extended periods.

B. Adults (19–64 years)

• Aerobic Target: Accumulate at least 150 minutes of moderate-intensity activity (e.g., brisk walking) OR 75 minutes of vigorous-intensity activity (e.g., running) per week (or a combination of both).
• Muscle Strengthening: Undertake activities that build muscle strength (e.g., carrying heavy loads, resistance exercises, yoga) on at least 2 days a week.
• Sedentary Time: Minimise sedentary time and break up long periods of sitting.

C. Older Adults (65+ years)

• Aerobic & Muscle Target: Same baseline as adults (at least 150 minutes of moderate-intensity activity and muscle strengthening on 2 days a week).
• Balance and Flexibility (Crucial Addition): Participate in physical activity to improve balance and flexibility on at least 2 days a week to reduce the risk of falls and maintain independence.

Key Takeaway: Remember the key numbers: 60 mins/day for youth (5–18), 150 mins moderate / 75 mins vigorous + 2 days strength for adults (19–64), and add 2 days balance/flexibility for older adults (65+).


In Unit AS 2, you must link physical activity directly to the prevention and management of key chronic health conditions.

1. Cardiovascular Disease (CVD)

Regular aerobic exercise strengthens the myocardium (heart muscle), leading to:
• Improved heart efficiency: Lower resting heart rate and increased stroke volume.
• Blood Pressure Regulation: Helps lower systolic and diastolic blood pressure by improving arterial elasticity.
• Improved Lipid Profile: Increases levels of high-density lipoprotein (HDL / "good cholesterol") and helps lower low-density lipoprotein (LDL / "bad cholesterol"), reducing plaque build-up in arteries (atherosclerosis).

2. Type 2 Diabetes

Physical activity plays a critical role in glucose control:
• Increased Insulin Sensitivity: Muscle contractions stimulate glucose uptake from the bloodstream directly into muscle cells, even when insulin levels are low or insulin resistance is present.
• Glycaemic Control: Regular activity helps maintain stable blood glucose levels and reduces HbA1c levels over time.

3. Obesity & Weight Management

• Energy Balance: Physical activity increases total Energy Expenditure (EE). When energy expenditure exceeds energy intake, a negative energy balance is achieved, leading to weight loss.
• Weight Maintenance: Regular activity is particularly effective for preventing weight regain following weight loss.

4. Bone Health & Osteoporosis

• Mechanical Loading: Weight-bearing activities (e.g., brisk walking, running, jumping) apply mechanical stress to bones.
• Bone Mineral Density (BMD): This stress stimulates bone-forming cells, increasing or preserving Bone Mineral Density (BMD) and reducing the risk of developing osteoporosis and fractures later in life.

Key Takeaway: Exercise protects health by improving heart function and lipid profiles (CVD), enhancing insulin sensitivity (Type 2 Diabetes), increasing energy expenditure (Obesity), and stimulating bone mineral density (Osteoporosis).


4. Common Exam Pitfalls & Examiner Tips

Be prepared for common mistakes that cost students marks in AS 2 exams:

• Mistake 1: Giving Vague Recommendations
Incorrect: "People should exercise for a bit every day to stay healthy."
Correct: "Adults aged 19–64 should achieve at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity physical activity per week."

• Mistake 2: Forgetting Muscle Strengthening
Many students describe aerobic fitness (walking, running) but forget to state the CMO requirement for muscle-strengthening activities on at least 2 days a week.

• Mistake 3: Overestimating Exercise Alone for Weight Loss
Examiners reward candidates who recognise that while physical activity increases energy expenditure, it is most effective for weight maintenance. For significant weight loss, physical activity must be combined with dietary changes (reduced energy intake).

• Mistake 4: Missing the Older Adult Specifics
When asked about older adults (65+), always mention the need for balance and flexibility training on at least 2 days a week to reduce the risk of falls.


Quick Review Summary Box

• METs: Sedentary (\(\le 1.5\)), Moderate (\(3\text{--}6\)), Vigorous (\(> 6\)). \(1\text{ MET} = 1\text{ kcal/kg/hour}\).
• 5–18 years: \(\ge 60\text{ mins}\) moderate-to-vigorous daily + variety of movement/bone/muscle activities.
• 19–64 years: \(\ge 150\text{ mins}\) moderate OR \(75\text{ mins}\) vigorous weekly + strength on \(\ge 2\text{ days}\).
• 65+ years: Same as adults + balance/flexibility on \(\ge 2\text{ days}\) to prevent falls.
• Disorders: CVD (improves HDL/LDL & blood pressure), Type 2 Diabetes (increases insulin sensitivity), Obesity (increases energy expenditure), Bone Health (increases BMD via weight-bearing exercise).