A–B. Active Living and Movement Competence · Active Living and Movement: Train with Purpose, Play with Strategy

What Shapes Fitness? Heredity, Growth and Nutrition

A2.2 1.1 1.5About 70 minutes

Learning goals

I can name the factors that influence personal fitness listed in the Grade 10 curriculum.
I can explain how heredity and growth and development affect fitness and how fast people improve.
I can explain how nutrition and hydration support activity, using Canada's Food Guide.
I can compare my progress with my own past, not with other people's bodies.

Words to know

heredity
Traits passed from parents to children through genes, such as height, limb length and muscle fibre mix.

slow-twitch muscle fibres
Muscle fibres that contract more slowly and resist tiring. They are well suited to endurance.

fast-twitch muscle fibres
Muscle fibres that contract quickly and powerfully but tire faster. They are well suited to speed and power.

growth spurt
A period of fast growth in height during puberty. Its timing varies a lot from person to person.

growth plate
An area of developing cartilage near the ends of long bones in children and teens, where bones grow in length.

carbohydrate
A nutrient in grains, fruit, vegetables and milk that is the body's main fuel for moderate to vigorous activity.

Remember from Grade 9

In PPL1O you learned the five health-related components (cardiorespiratory endurance, muscular strength, muscular endurance, flexibility, body composition), the six skill-related components, and the short-term and long-term benefits of fitness. You also learned that individual differences mean people respond differently to training.

Grade 10 asks a deeper question: what makes people's fitness different in the first place?

Hook: same plan, different results

Cousins Ella and Sam both start the same 6-week running plan. Same days, same distances. After six weeks, Ella has improved her 1.6 km time by 50 seconds; Sam by 20 seconds. Sam is frustrated: "I did everything right!"

He did. But fitness isn't only about the plan. Bodies differ because of genes, growth, food and sleep, life situations and more. Understanding this helps you judge your progress fairly.

What A2.2 asks of you in Grade 10

You should identify factors that influence the development of personal fitness. The curriculum names:

nutrition;
heredity;
social, economic and cultural factors;
growth and development;
physical limitations;
effectiveness of training methods and adherence to training principles (overload, individuality, specificity).

You should also explain the benefits of developing personal fitness as part of a healthy, active lifestyle. This lesson covers heredity, growth and nutrition; the next lesson covers the rest.

The six factors named in A2.2 that influence personal fitness. You can't control some of them (heredity, growth timing), you can partly control others (social, economic and cultural factors, physical limitations), and you can control a lot of your nutrition and how well you train.

Heredity: the hand you're dealt

Your genes influence:

body size and proportions (height, limb length);
the size of your heart and lungs;
your mix of muscle fibres: more slow-twitch fibres suit endurance; more fast-twitch fibres suit speed and power;
how quickly you respond to training. Studies of families and twins show that people on the same program improve by different amounts, partly because of genes.

But heredity is not destiny. Genes set a range; your training, sleep and nutrition decide where you land in that range. Almost everyone improves with regular training. And for lifelong health, the most important comparison is you now versus you before.

Growth and development

During puberty, bodies change fast, but not on the same schedule. Some teens start their growth spurt years before their classmates; on average, girls start earlier than boys. This affects fitness:

Early developers may be bigger and stronger for a while, which can give an advantage in some sports. Late developers often catch up or pass them later.
During a growth spurt, bones can lengthen faster than muscles and tendons adjust, so some teens feel tight or a bit less coordinated for a while.
Growth plates near the ends of long bones are still developing, so good technique, gradual progression and avoiding overuse (doing the same repetitive motion too much) matter.
Well-supervised strength training with good technique and suitable loads is considered safe and helpful for teens.

In youth sports, coaches sometimes pick the biggest kids, and studies of youth hockey in Canada have found more players born early in the year than late. Being a late developer is not the same as lacking talent.

Nutrition and hydration: fuel for activity

Canada's Food Guide suggests filling half your plate with vegetables and fruits, a quarter with whole grain foods and a quarter with protein foods, and making water your drink of choice.

For active teens:

Carbohydrates (whole grains, fruit, starchy vegetables, milk) are the main fuel for moderate to vigorous activity.
Protein (beans, lentils, nuts, tofu, fish, eggs, dairy, meat) helps repair and build muscle.
Fats (nuts, seeds, oils, fish) supply energy for long, easier activity and help absorb some vitamins.
Timing: a regular meal 2 to 3 hours before activity, or a small snack (fruit, yogurt, toast) about an hour before if you're hungry. After activity, a meal or snack with carbohydrate and protein helps recovery.
Hydration: drink water before, during and after activity, more in heat. For most workouts under about an hour, water is enough. Energy drinks are not sports drinks and are not designed for hydration.

Skipping meals before practice often means low energy, poor focus and slower recovery.

A plate built like Canada's Food Guide: half vegetables and fruits, a quarter whole grains and a quarter protein foods, with water to drink. Carbohydrates fuel activity, protein supports repair, and water replaces sweat losses.

Living skill: self-awareness (1.1)

Comparing your body or results with someone else's is unfair to you, because you don't share their genes, growth timing, history or situation. Ask instead: What have I improved? What helped? What can I control next? You can't change your genes, but you can control your training, sleep, food choices and effort.

Worked example

Let's explain Ella and Sam's results

Ella (15) improved her 1.6 km time by 50 s and Sam (15) by 20 s on the same plan. Ella had a growth spurt two years ago; Sam is growing fast right now and often skips breakfast before morning runs. Which factors might explain the difference? What should Sam do?

Heredity: they may differ in muscle fibre mix and how fast they respond to training. Neither can change this.
Growth and development: Sam is in a growth spurt. He may feel tight or less coordinated, and some of his body's energy is going to growth.
Nutrition: skipping breakfast before morning runs means less carbohydrate fuel, so his runs may feel harder and be slower.
What Sam controls: eat a small breakfast (toast and fruit, or yogurt) before runs, drink water, add gentle stretching for tight muscles, sleep well, and compare with his own starting time.

Sam's smaller improvement is likely due to heredity, his current growth spurt and under-fuelling. He did improve (20 s). He should fix what he can control (fuel, hydration, sleep) and judge progress against himself.

Worked example

Let's fuel for a 4 p.m. practice

Maya has basketball practice from 4:00 to 5:30 p.m. Lunch is at 11:45 a.m. School ends at 3:15. Plan her eating and drinking from lunch to dinner.

Lunch (11:45): a balanced meal: whole grain wrap with beans or chicken, vegetables, fruit, milk or water. This is over 4 hours before practice, so she will need a snack.
Snack (about 3:00 to 3:15): about an hour before practice: a banana and yogurt, or crackers and cheese. Mostly carbohydrate, easy to digest.
During practice: water bottle, sipping at breaks (more if the gym is hot).
After (by about 6:00): dinner with carbohydrate and protein (for example, rice, vegetables and fish or tofu) to refuel and help repair muscles.

Lunch, a carbohydrate snack about an hour before, water during practice, and a balanced dinner after.

Hands-on activity

Fitness influences inventory and fuel log

You need: a notebook, water bottle, and your regular activity sessions for three days.

Influences inventory (10 min): for each of the six A2.2 factors, write one way it affects your fitness. Mark each C (I can control it), S (I can partly control it) or N (I can't control it). For example: heredity N, nutrition C, growth N, training S.
Fuel log (3 days): each day, note when you ate before your activity, how much water you drank, how many hours you slept, and rate your energy during activity from 1 to 5. Do not count calories or weigh yourself; this is about timing and energy.
Look for patterns: were you more energetic on days with a snack about an hour before? With more sleep?
Plan one change you can control, such as packing a pre-practice snack.

Safety: do your normal activity, with a warm-up and cool-down. If you have food allergies or a medical diet, follow your health-care provider's advice. If thinking about food or body changes causes you worry, talk to a trusted adult or health professional.

Just for fun

Your muscles have "slow-twitch" and "fast-twitch" fibres. Sadly, there's no "homework-twitch" fibre, so homework still has to be done the slow way.

Your turn

List the six factors that influence personal fitness named in A2.2.

Name two traits influenced by heredity that affect fitness.

Which muscle fibre type suits a marathon? A sprint?

Why might a teen feel tight or less coordinated during a growth spurt?

Describe the Canada's Food Guide plate.

Which nutrient is the main fuel for moderate to vigorous activity?

Why is heredity "not destiny"?

More practice: warm-up

What is heredity?

Name one protein food.

What should be your drink of choice according to Canada's Food Guide?

On average, who starts puberty earlier, girls or boys?

When might you eat a small snack before activity?

More practice: on your own

A late-developing 14-year-old is cut from a hockey team. What would you tell him about growth and development?

Jaya feels sluggish at 7 a.m. swim practice. She doesn't eat beforehand. Suggest a plan.

Explain why comparing your fitness to a friend's can be unfair.

Why do good technique and avoiding overuse matter more for teens?

Is a sports drink needed for a 40-minute home circuit? Explain.

Challenge

Two runners: Runner A has mostly slow-twitch fibres, Runner B mostly fast-twitch. Predict which events each might find easier, and explain how both could still benefit from training their weaker area.

Plan a day of eating (no calorie counts) for a teen with a 6:00 a.m. hockey practice and a 7:00 p.m. ultimate game, using the Food Guide and timing guidelines.

"Fitness is all genetics, so training is pointless for most people." Write a three-point counter-argument using this lesson.

Check your understanding

Quiz

Which factor is mostly outside your control?

Fast-twitch muscle fibres are best suited to:

Canada's Food Guide suggests filling half your plate with:

The main fuel for moderate to vigorous activity is:

During a growth spurt, a teen may feel tight because:

Which is the fairest way to judge your fitness progress?

For parents and teachers

Big idea: Expectation A2.2 asks students to identify factors that influence the development of personal fitness: nutrition, heredity, social, economic and cultural factors, growth and development, physical limitations, and the effectiveness of training (overload, individuality, specificity), and to explain the benefits of fitness. This lesson covers heredity, growth and nutrition.

How to help at home:

Help your teen plan a pre-practice snack and keep a water bottle handy.
Encourage comparing with their own past results, not with siblings or friends.
If your teen is growing quickly and feels tight or clumsy, reassure them that this is common and temporary, and encourage gentle stretching and good technique.

Common difficulties:

Believing fitness is "all genetics". Remind them everyone improves with training.
Thinking sports drinks or energy drinks are needed. Water is enough for most activity under an hour; energy drinks are not for hydration.

Sensitive topic note: this lesson avoids weighing, calorie counting and body comparisons. If your teen shows worry about food, weight or body changes, talk with them supportively and consider contacting your family doctor or school counsellor.