Markers Of Acute Kidney Injury Following A Bout Of High-Volume Functional Resistance Exercise

Acute kidney injury (AKI) following extreme high-volume functional resistance exercise (HVFRE) has been observed. However, the breadth of programing within this exercise style and concomitant risk factors make causality unclear. PURPOSE: Measure markers of AKI after a standardized HVFRE workout. METHODS: Participants [n = 38 (10 female), 175 ± 9 cm, 79 ± 14 kg, 29 ± 9 y, with HVFRE experience of 3.7 ± 1.7 y] performed a HVFRE workout (1-mile run, 100 pull-ups, 200 push-ups, 300 body-weight squats, and 1-mile run). Exclusion criteria were current injury, renal disease, and no previous completion of the intervention HVFRE workout. Spot urine and blood samples were taken at five time points surrounding the workout (24 hr-pre, immediately-pre, immediately-post, 24 hr-post, and 48 hr-post). 24 hr urine was collected over three days (day before, day of, and day after workout) Spot urine was analyzed for protein and blood with reagent strips, blood was analyzed for interleukin-18 (IL-18), chitinase-3-like protein 1 (YKL-40), creatine kinase (CK), myoglobin (MYO), and 24 hr urine for neutrophil gelatinase-associated lipocalin (uNGAL) with enzyme-linked immunosorbent assays. RESULTS: HVFRE duration and intensity were 65 ± 14 min and 77.0 ± 11.7 %HRR, respectively. IL-18 (+27.4 ± 38.6 pg/mL) and YKL-40 (+14.6 ± 5.5 ng/mL) were elevated immediately-post exercise only in comparison to the immediately-pre time point (p < 0.01). There were no significant changes in corrected uNGAL from day-before, to day-of [+5.39 ± 21.47 (ng/ml)/(ml/min), p = 0.15] or day after exercise [+2.82 ± 15.46 (ng/ml)/(ml/min), p = 0.31]. Spot urine samples showed increased incidence of proteinuria (84%, p < 0.01) and hematuria (22%, p = 0.02) immediately following the bout of exercise. Significant increases from immediately-pre (224 ± 129 U/L; 69 ± 27 ng/mL) to all post exercise time points up to 48 hr (1380 ± 2354 U/L, p = 0.01; 283 ± 400 ng/mL, p < 0.01) were observed for CK and MYO, respectively. Nine of 38 subjects (24%) demonstrated CK > 5x resting at ≥1 post workout time point. CONCLUSION: Proteinuria, hematuria, IL-18 and YKL-40 increase immediately following HVFRE and return to baseline within 24 hr. CK and MYO remained elevated for at least 48 hr following the bout of exercise demonstrating some risk for AKI following this specific HVFRE.