(16) PHYSIOLOGICAL RESPONSES TO A MAXIMAL TREADMILL TEST AND 3-MINUTE ALL-OUT RUNNING TEST

Background: The heart rate (HR) at the Respiratory Compensation Point (RCP) has been linked the critical heart rate (CHR), or a HR delineation between heavy and severe intensity exercise. Establishing the CHR is accomplished with multiple exhaustive cycling or running trials. External workload delineations between heavy and severe intensity such as critical power or critical velocity (CV), may be measured in a three-minute all-out test (3MT). To date, it has not been reported if the HR achieved during a 3MT aligns with the HR at RCP (HR_RCP).

Purpose: To investigate the HR response during a sprint-based 3MT and compare the HR at critical velocity to the HR_RCP.

Methods: Eleven (1 female) participants volunteered for this study (24.18 ± 4.09 yrs, 1.77 ± 0.14 m, 80.54 ± 16.10 kg). Participants completed a maximal treadmill test (MAX-TM) where peak oxygen consumption (VO_2PEAK, mL/kg/min), minute ventilation (V_E, L/min), and carbon dioxide production (VCO₂, L/min) were directly measured using a calibrated metabolic cart system. The Respiratory Compensation Point (RCP) was determined by identifying the break in linearity between V_E and VCO₂. On a separate day, participants completed a sprint-based 3MT that included repeated 30-meter sprints with switchbacks for three minutes. Sprints were hand-timed, and the average sprint velocity in the final 30 seconds of the 3MT was used to represent critical velocity (CV, m/s). HR (bpm) was monitored continuously using a chest strap. From the MAX-TM, maximal HR (MHR_TM) and HR_RCP were extracted. Maximal HR from the 3MT (MHR_3MT) and average HR at CV (HR_CV) were also calculated. Post-exercise lactate (mmol/L) was measured via finger prick in the MAX-TM (LA_TM) and 3MT (LA_3MT). Paired samples t-tests were conducted to identify differences between MHR_TM and MHR_3MT, HR_RCP and HR_CV, and LA_TM and LA_3MT. Pearson-product correlations examined relationships between VO_2PEAK, MHR_TM, MHR_3MT, HR_RCP, HR_CV, LA_TM, and LA_3MT. An alpha of 0.05 determined statistical significance.

Results: Pairwise comparison indicated no significant difference (t₁₀ = 1.19, p = .263) between MHR_TM (191.64 ± 7.76 bpm) and MHR_3MT (189.00 ± 7.36 bpm). HR_CV (184.64 ± 5.61 bpm) was significantly higher (t₁₀ = 4.26, p = .002) than HR_RCP (168.91 ± 12.12 bpm) and significantly lower (t₁₀ = -4.71, p < .001) than MHR_3MT. LA_TM (10.90 ± 4.62 mmol/L) was significantly lower (t₁₀ = -3.81, p = .003) than LA_3MT (14.95 ± 2.60 mmol/L). Correlation results indicated significant negative relationships between VO_2PEAK and HR_CV (r = -.63, p = .04), LA_TM (r = -.73, p = .01), and LA_3MT (r = -.65, p = .03).

Conclusions: The results suggest that HR_CV during the 3MT represents a severe intensity heart rate that is higher than the HR_RCP from a MAX-TM. This indicates that it may not be feasible to determine the HR_RCP or critical heart rate from a sprint-based 3MT. Higher aerobic capacity was related to a lower cardiovascular and metabolic load of the 3MT, and the 3MT test may be useful for capturing severe-intensity metabolic load, as lactate response was significantly higher than the MAX-TM. PRACTICAL APPLICATIONS: A sprint-based 3MT may be a practical assessment of critical velocity and severe-intensity work capacity. Monitoring heart rate during the 3MT provides insight into severe intensity cardiorespiratory performance in that a lower HR_CV may indicate higher aerobic fitness. Future researchers should investigate how changes in HR_CV correspond to changes in VO_2PEAK.

Acknowledgements: None