My early childhood memories of cows milk always came with a strong message, “Drink up, it’s good for your bones!”. I’m not here to lobby for the dairy community, instead I offer a perspective that perhaps isn’t shared with most children which is, building big strong muscles is not just something you do to show off, your bones will also get bigger and stronger as a result!
What the research shows
This research looks at muscle size, muscle strength and physical performance and investigates the relationships for each of these with bone size, bone density and bone strength!
In very simple terms this is what the research shows.
Muscle Size
Bigger muscles are linked to bigger and stronger bones in both men and women.
There’s no link between muscle size and the density of bones in the wrist.
Grip Strength (Muscle Strength)
Stronger grip means bigger and stronger wrist bones in men.
The same trend is seen in women, but the link to bone size is weaker.
Bone density in the wrist doesn't depend on grip strength.
Gait Speed (Physical Performance)
How fast you walk has no connection to the size or strength of shin bones in both men and women.
There are a few hypotheses as to explain the results above, one of which will be explained briefly below.
The mechanostat hypothesis
The mechanostat hypothesis is a theory that explains how bones adapt to the mechanical loads placed on them. Here’s a simple explanation:
1. Bones Sense Load: Bones can sense the amount of stress or load they are under. This stress comes from activities like walking, running, lifting weights, or any physical movement.
2. Bone Remodelling: In response to this stress, bones undergo a process called remodelling. This involves breaking down old bone tissue and forming new bone tissue.
3. Strength Adjustment: If bones experience a lot of stress (like from lifting weights or carrying heavy loads), they respond by becoming denser and stronger to handle the increased load. Conversely, if bones experience very little stress (like from prolonged bed rest), they become weaker and less dense.
4. Optimal Strength: The goal of this process is to maintain optimal bone strength. Bones adjust their strength and density to be strong enough to handle typical loads but not so dense that they become unnecessarily heavy.
In short, the mechanostat hypothesis suggests that bones get stronger when they are regularly challenged by physical activity and weaker when they are not. This helps explain why exercise, particularly weight-bearing exercise, is important for maintaining strong bones.
Fun facts about the study
313 men and 318 women took part in the study, they were all from Hertfordshire in the UK.
Muscle strength was measured by grip strength.
Physical performance was measure by gait speed (a measure of how fast a person walks).
All measurements in were adjusted for things like height, weight, social class, smoking status, alcohol consumption, calcium intake etc.
Study limitations
Study Design: The study is cross-sectional, so it can't show cause and effect.
Grip Strength Measurement: Grip strength was measured on both hands, but bone measurements were taken only on the non-dominant side.
Bone Strength Estimate: Bone strength was estimated theoretically, not measured directly.
Bone Shape: The bones (radius and tibia) aren't perfectly circular, which may affect measurements.
Self-Reported Data: There are limitations in the accuracy of self-reported physical activity, diet, smoking, and alcohol use.
What are the take aways?
When you build muscle, you’re not just getting stronger on the outside, your bones are getting a serious upgrade too! It’s like your muscles and bones are best buddies. When one gets stronger, the other follows suit.
Yes, there are limitations in the study, but despite this the message is clear: regular, weight-bearing exercise is essential for bone health.
This was not a message I heard at all when I was a child BUT we live in a time of great access to information and the ability to share it so please do! In under 3 minutes this short blog could change someone’s opinion on going to the gym and lifting some weights!
Lastly, at BOOST we always encourage you to MOVE LIKE YOUR LIFE DEPENDS ON IT, because ultimately, it does!
Referencing
Original article name: Muscle Size, Strength, and Physical Performance and Their Associations With Bone Structure in the Hertfordshire Cohort Study
Original article location: https://.oup.com/jbmr/article-abstract/28/11/2295/7598545?redirectedFrom=fulltext&login=true#438714007
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