Question

Bob has been active all of his life. He played soccer from elementary school all the way through college. He even played on a community team but now at age 45, he’s been diagnosed with high blood pressure (hypertension). At times he ate too much junk food and occasionally drank too much alcohol but he couldn’t get around the fact that the men in his family all had high blood pressure. Dr. Miller, Bob’s primary care physician, had to prescribe two different antihypertensive medications in order to get his blood pressure under control. She also recommended Bob continue his regular soccer workouts but suggested a low-salt diet and more modest alcohol intake. Bob heeded Dr. Miller’s recommendations. His father and his 2 uncles had hypertension at a young ages, and all 3 men ended up on dialysis before dying from complications of kidney failure.Bob began the recommended lifestyle changes at age 45 and even started running regularly to keep his blood pressure under control. Now, 10 years later, he was a marathoner and participated in local marathons, competing with, and outrunning many his own age. However, Bob noticed that during the past several months, he’d experienced more fatigue than normal and some dehydration symptoms after his long runs. After consulting with Dr. Miller, Bob sought the help of Ty, an exercise physiologist, to help him maintain his exercise regime and his health without feeling “old”.Ty worked with Dr. Miller to make sure that Bob was monitored closely since he was still taking his anti-hypertensive medications. Ty suggested a urinalysis to assess Bob’s physical condition before, during and after his workouts. Bob dutifully supplied urine samples to Dr. Miller for evaluation as Ty recommended. Ty explained that Bob’s dehydration symptoms were more difficulty to evaluate since the medication Bob took to control his high blood pressure could affect his renal status or physiologic functioning.Dr. Miller logged the following results of Bob’s urinalysis immediately after, and six hours after, a rigorous 2-hour run.

Time	color	Specific gravity	protein	glucose	PH
Before exercise	pale yellow	1.002	none	none	6.0
Immediately after exercise	dark yellow	1.035	small amount	none	4.5
6 hours after exercise	yellow	1.025	none	small amount	5.0

Ty noted the color changes of Bob’s urine before, immediately after and 6-hours after his workouts. What do the color changes of Bob’s urine indicate?

Ty also noted that Bob’s specific gravity changed with each urine collection. Explain how Bob’s urine color/concentration compare to the urine specific gravity at the same time?

Answer 1

The color of urine changes to dark yellow from pale yellow immediately after exercise because of an increase in concentration due to dehydration during exercise. During exercise, the body sweats more and becomes dehydrated and the patient’s water intake during exercise is nil. The color of urine is an indicator to assess the dehydration level of an individual during exercise. Pale yellow color before exercise indicates proper hydration. Six hours after exercise, the hydration level increases with more fluid intake, and urine color changes from dark yellow to yellow. So the color changes of Bob’s urine indicate the level of dehydration.

Urine specific gravity also changes with exercise indicating dehydration. Here the highest specific gravity is seen in the sample obtained immediately after the exercise. This is because the color/concentration increases with increasing dehydration resulting in an increase in specific gravity. As the concentration is less before exercise, when the body is well hydrated, the specific gravity shows the least value. Six hours after exercise, specific gravity value decreases with increased fluid intake and less sweating and decreased concentration/color.