IB Syllabus focus: 'Physical activity can positively or negatively affect muscular and immune system function. Active lifestyles can reduce risks of osteoporosis, obesity, hypertension, cardiovascular disease and type 2 diabetes.'
Physical activity affects far more than fitness scores. It changes how muscles perform, how the immune system responds, and how likely a person is to develop several major chronic diseases.
Physical activity and muscular system function
Physical activity places stress on skeletal muscle. When that stress is appropriate and followed by recovery, muscles adapt and become more effective. When the activity is excessive, repetitive, or poorly controlled, muscular function can decline.
Positive effects on the muscular system
Regular activity improves the muscular system in several ways:
Resistance and weight-bearing activity stimulate muscle protein synthesis, helping increase strength and preserve lean mass.
Repeated training improves neuromuscular coordination, so muscles are recruited more efficiently.
Practice Questions
FAQ
After very long or exhausting exercise, the body may experience temporary immune disruption.
This can be linked to:
high stress hormone levels
glycogen depletion
dehydration
poor sleep
crowded travel environments after competition
The increased risk is usually short term, not permanent. It is more likely when hard exercise is combined with low energy intake or insufficient recovery.
Visceral fat is stored around internal organs, while subcutaneous fat is stored under the skin.
Visceral fat is more strongly linked to disease risk because it is metabolically active. It releases substances that promote inflammation, worsen insulin resistance, and negatively affect blood lipids. That is why physical activity that reduces visceral fat can have large health benefits even if total body mass changes only a little.
Resistance training can improve glucose regulation even when body weight stays similar.
It helps by:
increasing or preserving muscle mass
increasing the amount of tissue available to store glycogen
improving insulin sensitivity in muscle cells
increasing glucose transporter activity during and after exercise
So, metabolic health can improve even if the scale changes very little.
Swimming and cycling are excellent for cardiovascular fitness, but they place less impact force through the skeleton than running, jumping, or resistance training.
Because bone responds strongly to loading, athletes in mainly non-weight-bearing sports may need additional activities such as:
strength training
hopping or jumping drills
land-based conditioning
These activities provide a stronger stimulus for maintaining bone density.
Yes. A single session can produce short-term changes.
For blood pressure, some people experience post-exercise hypotension, meaning blood pressure stays lower for a period after activity. For immunity, immune cell numbers in the blood may rise during exercise and then shift during recovery.
These acute effects are not the same as long-term adaptation, but repeated acute responses help build chronic health benefits over time.
