Last updated on October 31, 2025
Question:
A question has been bothering me for a long time. I recently began researching PHV and its correlation with increases in sitting height and leg length. Every time I search for research on this topic, I find that the answers vary. Some say it occurs closer to the peak velocity of the trunk, while others suggest it occurs closer to the peak velocity of the legs. Therefore, my question is:
What segment exactly grows faster at PHV? Does it coincide more with the PHV of the legs or the trunk?
Answer:
Peak Height Velocity (PHV) is the point in time when a person grows the fastest during adolescence. Dr. Tanner used the PHV as the marker for the transition between stage 3 and stage 4. The problem is that PHV is more challenging to determine when it occurs. It is easy to find in retrospect.
It is during stage 3 that the legs grow the most, and during stage 4, the spine grows the most. Therefore, PHV is related to the growth of the legs. The spine grows at a slower rate.
On this site, I use a modified definition of stage 3 and stage 4. Stage 3 is the period when a person grows faster than their childhood rate of growth (typically 2 inches per year), and stage 4 is when growth slows back down to childhood rates or less. This definition is more straightforward to determine while it is occurring and has the nice side effect of causing stages 3 and 4 to both be about two years in length. Dr. Tanner’s original definition has stage 3 being roughly 6 months and stage 4 being about 3.5 years.