Final answer:
A third-trimester pregnant Soldier should avoid high-impact aerobics without Health Care Provider approval due to its intensity and potential risk to mother and baby.
Step-by-step explanation:
During pregnancy, especially in the third trimester, it's crucial to ensure that any exercise or cardio activities are safe for both the mother and the developing baby. Activities such as walking, swimming, and stationary cycling are generally considered safe and may be recommended by health care providers for pregnant women. However, high-impact aerobics can pose risks due to the high intensity and potential for jarring motions, which could affect the mother's and baby's well-being. Therefore, a third-trimester pregnant Soldier should not be allowed to participate in high-impact aerobics without Health Care Provider (HCP) approval.