Q.Explain different properties of muscles.
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Physiological Factors
Two athletes can follow the same training programme and end up with very different levels of fitness. Much of that difference comes down to physiological factors — the internal, body-level systems that determine how much strength, endurance, speed, and flexibility a person is capable of developing. Physical Education studies three physiological factors as the foundation of physical fitness.
The Skeletal Muscle Factor
Muscle is made of two broad fibre types. Type I (slow-twitch, slow oxidative) fibres are rich in capillaries, myoglobin, and mitochondrial enzymes, giving them a red colour. They work aerobically, resist fatigue, and favour long-duration activities like distance running, swimming, and cycling. Type II (fast-twitch, fast glycolytic) fibres have fewer mitochondria, are lighter in colour, work anaerobically, and fatigue quickly — they favour short, explosive efforts like jumps, throws, and sprints. The proportion of each fibre type a person has (partly genetic) shapes which fitness components come more naturally to them: long-distance runners typically carry 70–80% slow-twitch fibres, sprinters 70–75% fast-twitch, while non-athletes sit closer to an even split.
The Energy Production Factor
Every movement needs energy, and the body produces it through metabolism — anabolism (using energy to build tissue) and catabolism (breaking down fuel stores to release energy). Three energy systems supply this, matched to how long an effort lasts: the ATP-CP (phosphagen) system for activities under 10 seconds, such as a sprint start or a weightlifting attempt; the anaerobic system for efforts under about 2 minutes, such as a 400m race; and the aerobic system for longer-duration activities such as football or a marathon, where oxygen is used continuously to release energy.
The Cardiorespiratory Factor …
Muscles have four defining properties that together let them contract, respond, stretch and recoil. …
Muscles have four properties - contractility, excitability, extensibility and elasticity - that together let them contract on command, then stretch and recoil safely.
Section 7.1.1 names all four: Contractility is the muscle's ability to shorten and generate tension when stimulated, which is what produces movement. Excitability is its ability to receive and respond to a stimulus, typically a nerve impulse telling it to contract. Extensibility is its ability to be stretched beyond its resting length without being damaged. Elasticity is the complementary ability to return to its original resting length once the stret …
- CBSE 2026Set 75/SRP1Q/41 markMCQQ.Which of the following is the long-term effect of exercise on the respiratory system ? (A) Residual volume increases (B) Respiratory rate increases (C) Stroke volume increases (D) The rate of exchange of gas increases
›Reveal solutionSolution
The long-term effect of exercise on the respiratory system here is (A) Residual volume increases. Options (B) and (C) are wrong because a rising respiratory rate is a short-term response and stroke volume is a cardiovascular adaptation.
It helps to separate immediate (short-term) responses from lasting (long-term) adaptations. During a single bout of exercise, breathing speeds up at once to take in more oxygen — that is short-term. Long-term adaptations are the structural changes that build up over months of regular training.
Regular training enlarges the lungs and chest, strengthens the diaphragm and intercostal muscles, raises vital capacity and tidal volume, and brings more alveoli into use. Among the recognised long-term respiratory changes is an increase in residual volume — the volume of air remaining in the lungs after a maximal exhalation rises as overall lung capacity and chest expansion improve. That is exactly what option (A) states.
Taking the other options:
- (B) Respiratory rate increases — this is the immediate response to exercise. As a long-term adaptation the picture is the opposite: a trained person's resting respiratory rate tends to fall, because each breath becomes more efficient. …
- CBSE 2024Set 75/RQPS/41 markMCQQ.In which of the following fitness component an athlete gives better performance, if he/she has more slow twitch fibre in comparison to fast twitch fibres. (A) Speed (B) Strength (C) Endurance (D) Flexibility
›Reveal solutionSolution
Slow-twitch muscle fibres are built for sustained, aerobic activity and fatigue resistance, making them ideal for endurance performance rather than explosive speed or strength.
Muscle fibres come in two broad types, each suited to different kinds of physical work. Fast-twitch fibres contract quickly and powerfully but tire rapidly—they're the sprinter's asset, the weightlifter's tool. Slow-twitch fibres, on the other hand, contract more slowly and with less force, but they can keep working for a long time without fatiguing. This difference comes down to how each fibre type generates energy.
Slow-twitch fibres rely heavily on aerobic metabolism. They're packed with mitochondria (the cell's energy factories) and rich in myoglobin, which gives them a red colour and helps transport oxygen. Because they use oxygen efficiently to burn fat and carbohydrates, they can sustain activity for extended periods. Think of a marathon runner's legs working mile after mile, or a cyclist maintaining a steady pace for hours—that's slow-twitch dominance at work.
Fast-twitch fibres, by contrast, depend more on anaerobic pathways. They generate energy quickly without needing much oxygen, which is perfect for short bursts of maximum effort—a 100-metre dash, a heavy squat, an explosive jump. But this system produces lactic acid and depletes fuel stores rapidly, so fatigue sets in within seconds to a couple of minutes.
Now consider what each fitness component demands:
- Speed requires rapid, powerful muscle contractions—fast-twitch territory.
- Strength depends on generating maximum force, again favouring fast-twitch fibres.
- Flexibility is about joint range of motion and connective tissue elasticity, not really about fibre type at all.
- Endurance demands the ability to sustain effort over time, resisting fatigue—exactly what slow-twitch fibres are designed for. …
- CBSE 2019Set 75/BVM/41 markQ.Which method will you suggest to develop endurance ?
›Reveal solutionSolution
To develop endurance, use continuous training (steady aerobic work), interval training (alternating high and low intensity), fartlek training (speed play), and circuit training — all aimed at improving the body's ability to sustain prolonged physical effort.
Endurance is the capacity to sustain physical activity over an extended period, and it sits at the heart of almost every sport and fitness pursuit. Whether you're running a marathon, swimming laps, or simply trying to keep up with daily demands, your body's ability to deliver oxygen to working muscles and clear metabolic waste determines how long you can keep going. Developing endurance isn't about a single magic drill; it's about systematically training the cardiovascular and muscular systems to work efficiently under fatigue.
The most fundamental method is continuous training. This involves performing an activity at a steady, moderate intensity for a prolonged duration — think a 30-minute jog at a comfortable pace or a long swim without stopping. The beauty of continuous training lies in its simplicity and its direct impact on aerobic capacity. Your heart rate stays elevated in the aerobic zone (typically 60–80% of maximum heart rate), which trains the heart to pump more blood per beat, increases capillary density in muscles, and teaches the body to use fat as fuel. It's the bedrock method for building a strong aerobic base, especially for beginners or those returning to training after a break.
Once a base is established, interval training becomes invaluable. Here you alternate between periods of high-intensity effort and low-intensity recovery. For example, sprint for 400 meters, jog for 200 meters, and repeat. This method pushes the body into both aerobic and anaerobic zones, improving not just oxygen delivery but also the muscles' ability to tolerate and clear lactic acid. Interval training is time-efficient and highly effective for boosting VO₂ max — the maximum amount of oxygen your body can use during intense exercise, a key marker of endurance.
Fartlek training, a Swedish term meaning "speed play," blends the structure of intervals with the freedom of continuous running. You might run at a steady pace, then suddenly accelerate to a lamp post, ease off, sprint up a hill, recover, and so on — all within a single session. It's less rigid than formal intervals, making it mentally engaging and adaptable to terrain. Fartlek trains the body to handle unpredictable changes in pace, which mirrors the demands of many sports. …
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