Date Published: October 23, 2017
Publisher: Public Library of Science
Author(s): Maren. S. Fragala, Caixia Bi, Michael Chaump, Harvey W. Kaufman, Martin H. Kroll, Gotthard Kunze.
Physical exercise may affect levels of blood-based biomarkers. However, exercise status is seldom considered in the interpretation of laboratory results. This study reports the associations between habitual exercise participation and clinical laboratory test results.
The effects of days per week of aerobic and strength exercise participation on laboratory test results for 26 biomarkers in young adults aged 18 to 34 years (n = 80,111) were evaluated using percentile distribution analyses and multivariate regression.
In both men and women, more days per week of either aerobic or strength exercise were significantly associated with lower levels of glucose, hemoglobin A1c, LDL cholesterol, total cholesterol, triglycerides, estimated glomerular filtration rate, globulin, and C-reactive protein, and significantly higher levels of HDL cholesterol, creatinine, iron, and percent saturation (all p < .05). Type of exercise or gender influenced the observed relationships with exercise frequency for total cholesterol, aspartate aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, uric acid, bilirubin, and iron binding capacity. Physical exercise shifted the distribution of results into the direction suggestive of better health. Reported relationships may help clinicians and patients to better understand and interpret laboratory results in athletic populations and possibly re-evaluate interpretation of reference intervals for physically active populations.
Clinical laboratory tests provide information to screen, diagnose, and manage patient health and disease risk and status. While fitness and physical activity are recognized as important contributors to health and attenuating risk for cardiovascular diseases , information regarding the influence of aerobic and strength exercise participation on laboratory test results is sparse. Because clinical laboratory tests quantify key physiologic systems, changes in laboratory test values in terms of exercise frequency and type may offer a way to quantify improved fitness and reduction of risk of important chronic diseases, such as cardiovascular disease. In addition, results are usually interpreted in accordance with reported reference intervals that were established based on the middle 95% of a healthy population with similar characteristics . However, some evidence suggests that physical exercise may affect levels of clinical laboratory tests, where results may fall outside of the reported reference intervals in highly trained athletes . Characterization of the effects of exercise on clinical laboratory tests may offer a way to assess the significance of such observations.
We evaluated the effects of self-reported frequency (days per week) of aerobic and strength exercise participation on circulating levels of 26 blood-based biomarkers commonly evaluated in medicine using linear regression models and percentile distribution analyses. In accord with ethical standards this study was deemed exempt by the Western Institutional Review Board. Exception status was deemed as the research was based on the analysis of existing anonymized participant data.
The proportion of individuals without a reported health condition was higher for individuals reporting more days of strength or exercise participation. Younger age was associated with greater strength exercise participation, but the maximum effect in mean age was only 0.2 year for aerobic exercise and 0.67 year for strength exercise, thus clinically insignificant to account for the difference on biomarker levels. Physical exercise participation was related to clinical laboratory test results for a variety of biomarkers. The graphical presentation of the percentile distributions among the activity level groups for each marker is presented in Figs 1–4. According to the regression models (Table 2), more days of either aerobic or strength exercise were associated with lower levels of glucose, HbA1c, LDL, HDL ratio, triglycerides, eGFR, globulin, and CRP in both women and men. More days of participation in aerobic or strength exercise were associated with higher levels of HDL, creatinine, percent saturation, and iron in both men and women. Mode of exercise or gender (Figs 1–10) influenced the observed relationships between exercise frequency and cholesterol (total), bilirubin, A:G ratio, ALB, ALT, AST, ALP, calcium, ferritin, GGT, IBC, protein (total), and uric acid results. Predicted mean values based exercise frequency from the regression analysis for women and men participating in 0 and 5+ days of aerobic or strength exercise are shown in Table 3. Exercise frequency had no effect on TSH level in men or women.
This study reports that type (aerobic and strength) and frequency of exercise are related to a variety of clinical laboratory tests in healthy young adult men and women. In many cases the direction of the influence of exercise could be suggestive of better health. Yet mode of exercise and gender influenced the relationships between exercise and biomarker results for several measures for undefined reasons that require follow-up studies. Reported relationships may help in the understanding and interpretation of common laboratory results and avoid potential misinterpretation of acceptable results that may be a healthy adaptation to exercise training. Results may contribute to the eventual generation of laboratory reference intervals that are more appropriate based on factors such as physical activity.