Physical Exercises and Health
Senior 4 · Physical Education
Physical Exercises and Health
Lesson 2 of 4
25 min
Before you read on, place two fingers (not your thumb) on the thumb side of your wrist, count the beats for 15 seconds and multiply by 4. That is your heart rate in beats per minute (bpm). Ten minutes into a good warm-up it should have roughly doubled. This lesson explains why the first ten minutes of a session matter so much, how to set a heart-rate target that suits your body, and what balance and flexibility training do for your health now and for the rest of your life.
Definition
Activation exercises: light-to-moderate movements at the start of a session (jogging, skipping, leg swings, short accelerations) that prepare the heart, lungs, muscles and nerves for harder work. Together with mobility drills they form the warm-up.
Resting heart rate : beats per minute when fully at rest, best counted just after waking. Maximum heart rate : the highest rate the heart can reach in all-out effort.
Heart-rate reserve (HRR): , the range the heart can use above rest.
Balance: the ability to keep the body's centre of mass over its base of support, either standing still (static balance) or while moving (dynamic balance).
Proprioception: the body's sense of the position and movement of its joints, from sensors in muscles, tendons and ligaments.
Flexibility: the range of motion (ROM) available at a joint, measured as an angle in degrees or as a distance.
| System | Change during activation | Why it helps |
|---|---|---|
| Heart and blood vessels | Heart rate and stroke volume rise; vessels in working muscles widen | More oxygen reaches the muscles before hard work starts, so less early fatigue |
| Lungs | Breathing becomes deeper and faster | Oxygen supply matches demand; less "out of breath" feeling at the start of play |
| Muscles | Muscle temperature rises by a few degrees | Warm muscle contracts faster and stretches further before it is damaged |
| Nerves | Signals travel faster; reactions sharpen | Quicker, better-timed movements, so fewer awkward landings and collisions |
| Joints | Synovial fluid is spread over the joint surfaces | Smoother, less stiff movement at the knees, hips and shoulders |
| Mind | Focus moves to the task | Better concentration and confidence |
A target that ignores fitness and age is guesswork. Two steps give a personal one. First estimate the maximum heart rate. The traditional estimate is ; the Tanaka, Monahan and Seals (2001) formula is more accurate across ages:
Then use the Karvonen method, which applies an intensity (a fraction from 0 to 1) to the heart-rate reserve:
Activation work sits at about 50% to 60% of the reserve; hard training at about 70% to 85%. Remember that every formula only estimates your maximum: two people of the same age can differ by more than 10 bpm.
Worked example
Worked example 1: Ishimwe's heart-rate zones. Ishimwe is 16 with a resting heart rate of 64 bpm. Find his activation zone (50% to 60% HRR) and his hard-work zone (70% to 85% HRR).
With instead, his zones would come out about 4 bpm higher at activation level, which shows why the formula you use must be stated.
The graph shows Ishimwe's heart rate through a 40-minute lesson, with both zones drawn from Worked example 1.
Notice the shape: a steady climb into the activation zone (not a jump straight to the top), a main block in the work zone, and a gradual fall in the cool-down. A heart rate that is still high ten minutes after the session ends is a sign that the work was too hard for the pupil's present fitness.
Every time you land from a jump, change direction or are bumped in a game, your nervous system has a fraction of a second to bring your centre of mass back over your feet. Balance training improves the speed and accuracy of that correction, mostly by sharpening proprioception. That is why injury-prevention warm-ups in football, netball and basketball include single-leg exercises, and why balance work protects an ankle that has been sprained before.
| Make it harder by… | Easier version | Harder version |
|---|---|---|
| Reducing the base of support | Feet together | One foot; then on the toes |
| Removing vision | Eyes open | Eyes closed |
| Making the surface unstable | Firm floor | Folded mat or soft sand |
| Adding movement | Hold still | Catch and throw a ball; reach in three directions with the free foot; single-leg squat |
Health effects. Better balance means fewer ankle and knee injuries in sport now, better posture, and, much later in life, fewer falls: falls are a leading cause of injury in older people, and the balance you build and keep using as a teenager is the starting point for old age.
Worked example
Worked example 2: finding a weak side. In a stork-stand test (stand on one foot, the other foot against the knee, hands on hips, eyes closed), Mutesi holds 42 s on her left leg and 25 s on her right. Calculate the difference as a percentage of her better side, and interpret it.
Her right leg's balance is about 40% worse than her left. Mutesi tells the teacher she sprained her right ankle last term. A difference this large after a sprain suggests the ankle's proprioception has not fully recovered, and that she is at higher risk of spraining it again. Her plan: extra single-leg work on the right side (eyes open, then closed, then on a mat), re-tested after four weeks.
| Type | How it is done | Best used |
|---|---|---|
| Dynamic stretching | Controlled movement through the range: leg swings, walking lunges, arm circles, high knees | In the warm-up, after the pulse has been raised |
| Static stretching | Move to the end of the range and hold still, usually 15 to 30 seconds | In the cool-down, or in a separate flexibility session; only short holds inside a warm-up |
| PNF stretching | Stretch, contract the stretched muscle against a partner for a few seconds, relax, then stretch further | Separate flexibility sessions, with a trained partner |
Long static holds just before sprinting or jumping can briefly reduce power, which is why warm-ups favour dynamic stretches. Health effects of regular flexibility work include a larger range of motion, easier everyday movement, better posture and less stiffness after long periods of sitting in class. Flexibility is specific: a flexible hip says nothing about a stiff shoulder. It is measured joint by joint, as in the straight-leg raise below.
Worked example
Worked example 3: measuring progress. Habimana's straight-leg raise improved from 60° to 75° after six weeks of stretching three times a week (see the diagram). Find the percentage improvement.
For a fair re-test, the conditions must match the first test: same time of day, same warm-up, knee straight, the other leg flat on the floor, and the same person reading the angle.
Video: "Does Stretching/Warming Up Actually Help?", AsapSCIENCE. Watch for what a warm-up does to muscle temperature, and why the type of stretch and its timing matter.
Tip
Order of a warm-up: pulse, then move, then stretch on the move. Raise the heart rate into the activation zone first; then mobilise joints; then use dynamic stretches that copy the movements of the sport. Save long static holds for the cool-down.
Warning
Common mistakes. Counting the pulse with the thumb (it has its own pulse). Forgetting to state which formula was used. Bouncing hard at the end of a static stretch. Testing balance only on the "good" leg. Treating a high heart rate after a short warm-up as fitness: it usually means the warm-up started too hard.
Practice
Remember
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
Quick check
