Physical Exercises and Health (Senior 4 Physical Education): free lessons | Ganzaa

Physical Exercises and Health

Lessons

Senior 4 · Physical Education

Physical Exercises and Health

4 lessons

Lesson 1 of 4

Safety and hygiene during physical and sports exercises

25 min

The last kilometre

At the Kigali International Peace Marathon, first-aiders in high-visibility vests wait near the finish inside the stadium. Most runners never need them. The few who do have usually met one of a short list of problems: too much heat, too little water, a twisted ankle, or a body pushed beyond what it was prepared for. Almost every one of those problems can be predicted, and so reduced, before the race starts.

In Senior 1 to Senior 3 you learned to warm up, to cool down and to plan a conditioning programme. This lesson goes one level deeper. You will assess the risks of a PE session the way a coach does, calculate how much water your body loses through sweat, learn the hygiene that stops infections spreading in a team, and practise the first aid that the European Resuscitation Council (ERC) recommends in its 2025 guidelines.

Definition

Hazard: anything that could cause harm, such as a hole in the pitch, a loose goalpost or strong midday sun.

Risk: how likely the harm is, combined with how serious it would be. A coach often scores it as $\text{risk} = \text{likelihood} \times \text{severity}$ , each on a scale of 1 to 3.

Control measure: an action that removes a hazard or lowers its risk, for example filling the hole or moving training to the early morning.

Hygiene: the habits that keep the body, kit and sports facilities clean so that infections do not spread.

Dehydration: a loss of body water that is not replaced. In sport it is measured as the percentage of body mass lost during the session.

Exertional heat stroke: a life-threatening rise in core body temperature during hard exercise, usually above 40 °C, with confusion, agitation, seizures or collapse.

Concussion: a brain injury caused by a blow to the head or body, which disturbs thinking, balance or behaviour, even without loss of consciousness.

Managing risk in a PE session

A teacher cannot remove every danger from sport; running and tackling are part of the game. The aim is to find each hazard, judge its risk and put the strongest control on the highest risks. Hazards come from four places.

Source	Typical hazards	Control measures
Environment	Stones, holes and broken glass on the field; wet or dusty surfaces; lightning; strong sun between about 11:00 and 15:00	Walk the field before the lesson; train early or late in hot weather; stop all play outdoors when thunder is heard and shelter in a building
Equipment	Goalposts that are not anchored; damaged balls, hurdles or mats; poles left on the ground	Anchor or weigh down portable goals; check and remove damaged items; store equipment away from the playing area
The body	Illness or fever; a recent injury; fatigue; no breakfast; asthma or diabetes	Ask about health before hard exercise; adapt the work; inhalers and glucose kept nearby; no exercise with a fever
People and organisation	Too many players in a small space; throwing events next to running events; no adult watching	Clear zones and spacing; one direction for throwing, with everyone behind the thrower; a teacher present at all times

Worked example

Worked example 1: scoring and ranking risks. Before a Senior 4 football lesson, the teacher notes three hazards. Score each on likelihood (L) and severity (S), each from 1 (low) to 3 (high), and decide which to deal with first.

Hazard	L	S	$\text{Risk} = L \times S$
A portable goal that is not anchored (it can tip over if a pupil hangs on the bar)	2	3	6
Patches of loose gravel near one touchline	3	1	3
A 14:00 lesson in full sun in the dry season	2	2	4

Decision. The goal comes first (risk 6): a falling crossbar can kill, so the goal is pegged or weighted before anyone plays. Next the heat (risk 4): shorten the work periods, add shaded water breaks or move the lesson to the morning. Last, the gravel (risk 3): rake it or mark the area out of play. Notice that the most likely hazard is not the most serious; multiplying the two scores puts them in the right order.

Heat, sweat and water

Your muscles turn only about a quarter of the chemical energy they use into movement; the rest becomes heat. During hard exercise that heat must leave the body as fast as it is made, mainly by the evaporation of sweat. When the air is hot and humid, sweat drips off instead of evaporating, heat is stored, and core temperature rises.

Sweat is mostly water, so the lost water can be measured with a bathroom scale. The National Athletic Trainers' Association (NATA) of the United States gives this method:

\text{sweat loss (L)} = m_{\text{before}} - m_{\text{after}} + V_{\text{drunk}} - V_{\text{urine}}

\text{sweat rate} = \frac{\text{sweat loss}}{\text{exercise time}} \qquad \text{body-mass loss (\%)} = \frac{m_{\text{before}} - m_{\text{after}}}{m_{\text{before}}} \times 100

Masses are in kilograms and volumes in litres, using $1\,\mathrm{kg}$ of sweat $\approx 1\,\mathrm{L}$ . NATA advises keeping body-mass loss below 2% by the end of exercise, because larger losses reduce both performance and the body's ability to lose heat. After exercise it advises drinking 100% to 150% of the fluid deficit.

Worked example

Worked example 2: a sweat test in Bugesera. Uwase weighs 58.0 kg before a 90-minute athletics session on a hot afternoon. She drinks 0.6 L of water during the session and does not use the toilet. Afterwards she weighs 57.1 kg. Find her sweat rate, her body-mass loss, and how much she should drink afterwards.

Sweat loss: $58.0 - 57.1 + 0.6 - 0 = 1.5\,\mathrm{L}$
Time: $90\,\text{min} = 1.5\,\text{h}$ , so $\text{sweat rate} = \frac{1.5\,\mathrm{L}}{1.5\,\mathrm{h}} = 1.0\,\mathrm{L\,h^{-1}}$
Body-mass loss: $\frac{58.0 - 57.1}{58.0} \times 100 = \frac{0.9}{58.0} \times 100 = 1.6\%$ This is below the 2% guide, so her drinking plan worked.
Her remaining deficit is 0.9 kg, about 0.9 L. Replacing 100% to 150% means drinking about $0.9$ to $1.4\,\mathrm{L}$ over the next few hours.

What if she had drunk nothing? She would have finished at $58.0 - 1.5 = 56.5\,\mathrm{kg}$ : a loss of $\frac{1.5}{58.0} \times 100 = 2.6\%$ , above the 2% guide.

Hygiene in sport

Sport brings bodies, sweat, shared balls and shared changing rooms together, which is exactly how skin, gut and respiratory infections spread. Good hygiene protects the whole team.

Habit	Why it matters
Use your own water bottle and towel	Saliva and skin germs pass from mouth to mouth and skin to skin on shared items
Wash with soap and dry well after exercise, especially between the toes	Warm, damp skin lets fungi grow; athlete's foot (a fungal infection) spreads on wet floors
Wash your PE kit and socks after each use	Sweat-soaked cloth breeds bacteria and causes skin irritation and smell
Cover cuts and grazes; clean any blood on equipment	Open skin lets germs in, and blood can carry infections to others
Keep nails short; remove jewellery and watches	Prevents scratches, torn skin and fingers caught in rings or nets
Wash hands with soap before eating and after the toilet	Stops diarrhoeal infections, which spread fast in boarding schools and teams
Eat a light meal 2 to 3 hours before hard exercise	A full stomach causes cramps and nausea; an empty one causes dizziness
Stay home from sport with a fever or diarrhoea	Exercise with a fever strains the heart, and the illness spreads to team-mates

Girls can take part in all sport during menstruation. Changing pads or other products as needed, washing, and having clean, private toilets with water at school are part of hygiene too.

Important

First aid in a PE session (ERC Guidelines 2025 and ILCOR 2025)

Suspected heat stroke (very hot body with confusion, agitation, seizures or collapse during exercise in heat): call 912. Move the person out of the heat into shade and remove excess clothing. Start active cooling at once. The best method is whole-body (neck down) immersion in cold water at 1 to 26 °C, for example in a tub; otherwise pour cold water over the body continuously while fanning, or use ice packs and wet towels. Without a thermometer, keep cooling for 15 minutes or until the confusion clears, whichever comes first. Cool first, transfer second, and keep cooling on the way.
Suspected concussion after a knock (headache, dizziness, nausea, blurred vision, confusion, sleepiness, changed behaviour): remove the player from the activity and send them to a health professional. Never let them "play on".
Dehydration after exercise: give water or any rehydration drink that is available; a sports drink with 4% to 9% carbohydrate and salts is suggested.
Twisted ankle: stop and rest. A cold pack wrapped in cloth, for no more than 10 minutes at a time, can ease pain and swelling; never put ice straight on the skin. A compression bandage may be used or left off: ILCOR finds neither choice better. Seek medical help if the person cannot put weight on the foot.
Severe bleeding: press firmly and directly on the wound.
Unresponsive and not breathing normally: call 912, start chest compressions (CPR) and send someone for a defibrillator (AED).

Video: "What happens when you get heat stroke?" by Douglas J. Casa, TED-Ed. Watch how the body's cooling system can fail during exercise, and why cold-water immersion within minutes saves lives.

Tip

Two numbers to remember. 2%: finish a session having lost less than 2% of your body mass. 40 °C: a hot, confused athlete is a heat-stroke emergency; cool first, transfer second.

Warning

Common mistakes. Wrapping a collapsed, overheated runner in a blanket "for shock" traps the heat. Waiting for an ambulance before cooling wastes the minutes that matter most. Sharing one water bottle across a team spreads infection. A player who "feels fine" after a blow to the head has not been cleared to continue. Ice held straight on the skin for a long time can injure it.

✦

Practice

Name one hazard from each of the four sources (environment, equipment, the body, people and organisation) for a volleyball lesson on an outdoor court.
A hazard has likelihood 3 and severity 2. Another has likelihood 1 and severity 3. Calculate both risk scores and say which should be controlled first.
Gatete weighs 70.0 kg before a 2-hour training session and 68.6 kg after. He drank 1.0 L and passed 0.2 L of urine. Calculate his sweat loss and sweat rate.
Calculate Gatete's body-mass loss as a percentage and say whether he met the NATA guide.
Explain why heat stroke is more likely on a hot, humid day than on a hot, dry day at the same temperature.
Put these heat-stroke steps in order: keep cooling during transfer; move into shade; call 912; start cold-water cooling; remove excess clothing.
A team shares two water bottles at a tournament "to save money". Evaluate this decision and suggest a better plan.
After a header, a striker says she has a headache but wants to keep playing because it is the final. Using the ERC 2025 guidance, explain what the coach must do and why.

Show answersHide answers

For example: environment, sun glare or a slippery court after rain; equipment, a net post that is not secured; the body, a pupil recovering from a sprained ankle; people, spectators standing too close to the court.
$3 \times 2 = 6$ and $1 \times 3 = 3$ . Control the first (risk 6) first, although the second still needs a control because its severity is high.
Sweat loss = 70.0 − 68.6 + 1.0 − 0.2 = 2.2 L. Sweat rate = 2.2 ÷ 2 = 1.1 L per hour.
(70.0 − 68.6) ÷ 70.0 × 100 = 2.0%. He reached the 2% limit, so he should drink more during the next session.
Humid air already holds a lot of water vapour, so sweat evaporates slowly and drips off without removing heat. Heat is stored and core temperature rises faster.
Call 912 → move into shade → remove excess clothing → start cold-water cooling → keep cooling during transfer. (Calling and moving into shade can happen together.)
Poor decision: shared bottles pass saliva-borne infections through the whole squad just before matches. Better: each player brings a named bottle, refilled from a clean container; or cups used once.
Remove her from play at once and refer her to a health professional; a headache after a blow to the head is a sign of concussion. Playing on risks a second injury to a brain that is already hurt; the importance of the match does not change this.

Quick check

Keza weighs 60 kg before a session and 58.5 kg after it. What percentage of her body mass has she lost?

Remember

Risk = likelihood × severity: control the highest risks first, starting with anything that could kill.
Sweat loss = mass before − mass after + fluid drunk − urine; keep body-mass loss below 2%.
Own bottle, clean kit, dry feet, covered cuts, washed hands: hygiene protects the whole team.
Heat stroke: call 912, shade, cool at once with cold water, cool first and transfer second. Concussion: remove and refer.

Sources and credits

McDermott B. P. and others, National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active, Journal of Athletic Training 52 (2017) 877–895: the sweat-loss formula, the 2% guide and the 100% to 150% replacement advice are summarised, not copied.
Djärv T. and others, European Resuscitation Council Guidelines 2025: First Aid, Resuscitation 215 (2025) 110752: the heat-stroke, concussion and bleeding steps are summarised, not copied.
2025 International Consensus on First Aid Science With Treatment Recommendations, International Liaison Committee on Resuscitation (ILCOR): rehydration drinks and the compression bandage for ankle injuries.
Strains and sprains, British Red Cross: the 10-minute limit for a cold pack.
912 ambulance number: SAMU Services, Rwanda Biomedical Centre.
Photo: Medical personnel interventions at the Kigali peace marathon, Isma250, Wikimedia Commons, licensed under CC BY-SA 4.0.
Video: "What happens when you get heat stroke? - Douglas J. Casa", TED-Ed, embedded from YouTube.
Heat-balance diagram, risk table, worked examples, practice and quick check: written by Ganzaa.

1The last kilometre

2Managing risk in a PE session

3Heat, sweat and water

4Hygiene in sport

The last kilometre

Managing risk in a PE session

Heat, sweat and water

Hygiene in sport