Interrater reliability of a customized submaximal cycle ergometer test

Purpose: Graded exercise testing (GXTs) is used to determine maximum oxygen uptake (V˙ O _{2 max}). Recently, customized submaximal exercise testing (CSET) completed on both treadmill and cycle ergometry were validated. Methods: Interrater reliability of the CSET for cycle ergometry was examined. Thirteen participants (age 31 ± 10.2 y, weight 77.9 ± 10.5 kg, height 176.2 ± 9.9 cm, body mass index 25.1 ± 2.9) completed the 2-stage × 3-min CSET protocol performed by two separate testers. True V˙ O _{2 max} was determined using the highest value derived by a GXT and verification bout. Skeletal muscle oxygen saturation (S˙ mO₂), measured using near-infrared spectrometry on the medial gastrocnemius muscle, and V˙ O ₂ were monitored during each CSET; whereby, V˙ O ₂ kinetics were modeled breath-by-breath data for each 3-min stage. Measurement agreement was quantified using intraclass coefficient (ICC), typical error (TE), and coefficient of variation (CV). Results: “True” V˙ O _{2 max} (ml·kg⁻¹·min⁻¹) between the GXT (41.3 ± 10.5) and verification (42.5 ± 11.5) was established (ICC = 0.98, TE: 0.98, CV 2.1%). Estimated V˙ O _{2 max} by tester 1 (42.5 ± 9.8) and tester 2 (42.7 ± 8.9) did not differ from “true” V˙ O _{2 max} (F_2,36 = 0.02, p = 0.98, η_p² = 0.00). The second stage evoked a V˙ O ₂ slow component of 194 ± 124 ml·min⁻¹ that corresponded with a time-dependent decline of S˙ mO₂. The mean S˙ mO₂ from the two CSET testers were highly correlated (ICC = 0.91, TE: 4.1%, CV = 8.9%). Conclusions: The CSET is a reliable and valid procedure and S˙ mO₂ is a useful tool for corroborating the second stage is in the heavy-intensity domain.