Body Systems, Measuring Activity, and Designing a Programme

What this course is asking of you

There is no written examination. The 50 marks come from attendance, a case study or micro project, and activity evaluation. So the useful question is not "what will be asked" but "what should I actually do" — and the honest answer is: build one habit that survives the semester.

That is what the FITT principle below is for.

The systems involved

Respiratory — brings oxygen in and removes carbon dioxide. Trained people breathe more efficiently rather than merely faster.

Cardiovascular — heart, blood and vessels, delivering oxygen to working muscle. The clearest sign of training is a lower resting heart rate: the heart pumps more per beat, so it needs fewer beats.

Musculoskeletal — bones, joints and muscles. The major groups worth naming: chest (pectorals), back (latissimus dorsi, trapezius), shoulders (deltoids), arms (biceps, triceps), core (abdominals, erector spinae), legs (quadriceps, hamstrings, gluteals, calves).

Bone responds to load. Weight-bearing exercise in your twenties builds the peak bone mass that determines your osteoporosis risk decades later — which is why this matters now rather than later.

Quantifying activity: the MET

One MET (metabolic equivalent of task) is the energy cost of sitting quietly, about 3.5 ml of oxygen per kg per minute. Activities are expressed as multiples.

Energy expenditure:

The exercise continuum

• Light — under 3 METs. Slow walking, light housework.
• Moderate — 3 to 6 METs. Brisk walking, cycling on level ground. You can talk but not sing.
• Vigorous — above 6 METs. Running, fast cycling, most sport. You cannot say more than a few words without pausing for breath.

The talk test is the practical version of this table and needs no equipment. Use it.

WHO guidance for adults: at least 150 minutes of moderate or 75 minutes of vigorous activity per week, plus muscle strengthening on two or more days.

Aerobic and anaerobic

Aerobic — "with oxygen". Moderate intensity, sustained for minutes or hours. Fuelled by oxidation of carbohydrate and fat. Builds cardiovascular endurance. Walking, jogging, cycling, swimming.

Anaerobic — "without oxygen". High intensity, sustained only seconds to about two minutes. Fuelled by stored ATP, creatine phosphate and glycolysis, producing lactate. Builds strength and power. Sprinting, weight lifting, jumping.

The distinction is duration and intensity, not the exercise itself. A slow cycle is aerobic; an all-out sprint on the same bicycle is anaerobic. Any sustained effort is mostly aerobic, because the anaerobic systems simply cannot supply energy for long.

Health-related components of fitness

The syllabus names five, and they are the axes a programme should cover:

1. Cardiorespiratory fitness — sustaining activity. The single strongest predictor of long-term health among the five.
2. Muscular strength — maximum force in one effort.
3. Muscular endurance — repeated force over time.
4. Flexibility — range of motion at a joint.
5. Body composition — proportion of fat to lean mass. More informative than weight alone, which is why a muscular person can have a "high" BMI and excellent health.

The FITT principle

How to build a programme, and how to progress it.

• F — Frequency. How often. Start 3 days a week; work toward 5.
• I — Intensity. How hard. Moderate to begin, judged by the talk test.
• T — Time. How long per session. 20–30 minutes to start.
• T — Type. What activity. Choose something you will actually keep doing — the best exercise is the one you do not quit.

Progressive overload: the body adapts to what it is given, so the demand must increase gradually or improvement stops. Change only one FITT variable at a time, by roughly 10% a week. Increasing frequency, intensity and duration together is the standard route to injury and to giving up in week three.

Every session: warm-up 5–10 minutes, main activity, cool-down and stretch 5–10 minutes.