Urinary Protein Excretion after Low-Intensity Walking in Healthy Japanese Elderly Women

Postexercise proteinuria is a well-considered phenomenon in humans. The purpose of this study was to determine if low-intensity walking on underwater and land treadmills would induce urinary protein excretion in elderly people. Urinary protein concentration was measured on 10 healthy elderly women during the normal fasting state, both before and immediately after underwater and land treadmill walking at a speed of 2.0 Km/h for 15 min. As indicators for assessing physiological responses to the walking, we used heart rate, skin blood flow, muscle hardness, and subject judgment scores (ratings of thermal sensation, comfortable sensation, and perceived exertion). In the underwater treadmill walking, urinary protein concentration corrected for creatinine (CRE) concentration increased significantly (P = 0.013) after the walking (666 mg/gCRE) than before the walking (404 mg/gCRE), although none of the measured indicators of heart rate, skin blood flow, muscle hardness, or mean subjective judgment scores changed significantly after the walking. The increase in the corrected urinary protein concentration was attributed to the decreased urinary CRE concentration after the walking. In the land treadmill walking, however, none of the indicators significantly changed after the activity. Urinary protein excretion after underwater treadmill walking may reflect the greater resistance to movement encountered in water than on land. Although further studies applying different walking intensity are needed, the possibility that urinary protein can be used as an indicator to assess walking intensity in the elderly women could not be ruled out. Our results provide preliminary rationale for further studies on basic information for promoting walking for elderly women.