Final answer:
The 19-year-old 800m freestyle swimmer would most likely have the most limited bone mineral density, since swimming is a non-weight-bearing activity and such exercises are essential in achieving optimal peak bone mass.
Step-by-step explanation:
In determining which athlete might have limited bone mineral density levels, we need to consider the force vectors and physical demands of each sport. Gymnasts, like the 16-year-old mentioned, frequently experience high-impact forces that promote bone density. Offensive linemen lift heavy weights, which also promotes bone density.
Track cyclists require strong legs for power, promoting bone density through resistance training; however, the 33-year-old cyclist's activity is less weight-bearing compared to other activities mentioned. Lastly, the 19-year-old 800m freestyle swimmer, despite having dry land training, may have lower bone density due to the non-weight-bearing nature of swimming.
Given these considerations, the swimmer is likely to have the most limited bone mineral density. This is corroborated by knowledge that bone mass peaks around 30 years of age and demands weight-bearing exercise to develop optimally.
The swimmer's sport, while cardiovascularly demanding, lacks the weight-bearing impact that is provided by sports such as gymnastics and weightlifting, which are integral in achieving higher peak bone mass and preventing conditions like osteoporosis.