Modality-Specific Heart Rate Differences at Ventilatory Thresholds During Unified Ramp Testing

Evaluation of Heart Rate and Ventilatory Threshold Agreement Between Cycling and Running Under Strictly Standardized Ramp Conditions

The purpose of this study was to investigate the heart rate bias between cycling and treadmill exercise at ventilatory thresholds. This was a randomized crossover trial involving 23 healthy participants. Each participant performed both cycling and treadmill exercise tests in a randomized order. The primary outcome was to determine the difference in heart rate response at the first and second ventilatory thresholds between the two exercise modalities. We hypothesized that there is a fixed bias in heart rate response, which may have implications for exercise prescription in clinical and rehabilitation settings.

Study Overview

• Status: Completed
• Conditions: Heart Rate; Exercise Physiology; Exercise (EX); Ventilatory Threshold; Cycling and Treadmill Exercise
• Intervention / Treatment: Device: Cycle Ergometer CPET; Device: Motorized Treadmill CPET (Porszász Protocol)

Detailed Description

Participants Twenty-three healthy adults (12 men, 11 women; age 30.8 ± 5.6 years; BMI 21.8 ± 2.6 kg/m²) were recruited via institutional advertisements at a university hospital. Inclusion criteria were: age ≥ 20 years, familiarity with cycling and treadmill exercise, and a negative Physical Activity Readiness Questionnaire response. Exclusion criteria were: history of cardiovascular, pulmonary, or metabolic disease; musculoskeletal injuries limiting exercise range of motion; or medications affecting heart rate or ventilation. Participants fasted for 3 hours, abstained from vigorous exercise, alcohol, and caffeine for 24 hours prior to testing, and provided written informed consent. Data collection was conducted between February 2024 and November 2024. The protocol was approved by the Institutional Review Board of National Taiwan University Hospital (IRB Registration: 202311036RIND).

Experimental Design A randomized crossover design was employed. Participants completed two symptom-limited CPET sessions on a cycle ergometer (VIAsprint, Ergoline, Germany) and motorized treadmill (Ergosprint, Ergoline, Germany), separated by 7-14 days and conducted at the same time of day (±2 hours) to control for circadian effects. The randomized order minimized potential order effects and ensured that fatigue from the first test did not systematically bias results.

Cardiopulmonary Exercise Testing Protocol Gas Exchange Measurement and Safety Monitoring Breath-by-breath gas exchange was measured using a metabolic cart (Vmax Encore, CareFusion, USA), calibrated before each test with standard gases and a 3-L calibration syringe. Heart rate was monitored continuously via 12-lead electrocardiography (Cardiosoft, GE Healthcare, USA), providing greater temporal resolution than telemetric methods. Blood pressure was measured at rest and every 2 minutes during exercise to monitor safety and detect cardiovascular abnormalities.

Unified Ramp Protocol The central innovation was implementing a unified ramp protocol on both modalities to eliminate kinetic confounding.

Cycle Ergometer: Following a 3-minute unloaded warm-up (0 W), continuous ramp increases began at 20 W·min-¹ (men) or 15 W·min-¹ (women), targeting an 8-12 minute test duration to optimize threshold identification within a physiologically relevant window.

Treadmill: Using the Porszász algorithm, simultaneous adjustments to speed and grade produced metabolically equivalent work rate increases (20 or 15 W·min-¹), matched to cycling. Warm-up consisted of 3 minutes at 3-4 km/h, 0% grade. The Porszász protocol mathematically calculates the non-linear combination of speed and grade increases needed to produce a linear rise in metabolic demand, ensuring identical oxygen uptake kinetic demands despite different biomechanical constraints.

Maximal Effort Verification Participants exercised to volitional exhaustion or until safety criteria were met. Maximal effort was confirmed by meeting ≥2 of the following criteria: respiratory exchange ratio (RER) ≥ 1.10; heart rate within 10 bpm of age-predicted maximum (220 - age); rating of perceived exertion (RPE) ≥ 17 on the Borg 6-20 scale; or VO₂ plateau (≤150 mL·min-¹ increase despite increasing workload).

Threshold Determination Breath-by-breath gas exchange data were binned into 5-second moving averages to attenuate noise while preserving dynamic resolution at the threshold transition point. VT1 and VT2 were identified independently by two blinded, experienced raters using consensus criteria (V-slope method, ventilatory equivalents, end-tidal gas tensions). Blinding was maintained by removing all identifiers before threshold determination. Disagreements (2 cases) were adjudicated by a third blinded expert. Inter-rater reliability was excellent (ICC = 0.94 for VT1; ICC = 0.96 for VT2). Variables were extracted as 30-second averages centered on the identified threshold time point to ensure stability.

Statistical Analysis Primary and Secondary Outcomes Primary outcome: heart rate difference at VT1 and VT2 between modalities. Secondary outcomes: absolute and relative VO₂, EqO₂, EqCO₂, and O₂ pulse.

Data Analysis Methods Data normality was assessed using the Shapiro-Wilk test. Paired t-tests compared variables between modalities, with two-tailed significance testing at α = 0.05. Intraclass correlation coefficients (ICC; two-way mixed-effects, absolute agreement) assessed measurement reliability. Measurement error was quantified using the coefficient of variation (CV = SD of differences/mean), which normalizes variability to enable comparison across variables with different scales.

Bland-Altman Regression Analysis for Proportional Bias Bland-Altman analysis with linear regression tested for fixed versus proportional bias-the core statistical innovation distinguishing this study. The difference between modalities (Cycling - Treadmill) was regressed against the mean of the two measurements. A non-significant regression slope (p > 0.05) indicated fixed bias, whereas a significant slope (p < 0.05) indicated proportional bias. This approach directly tests whether correction factors should be constant across participants or adjusted based on individual physiological capacity.

All statistical analyses were performed using SPSS Statistics Version 20 (IBM Corp., Armonk, NY) for ICC and t-tests, and GraphPad Prism Version 10 (GraphPad Software, San Diego, CA) for Bland-Altman plots.

• Study Type: Interventional
• Enrollment (Actual): 23
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Taiwan
  • Taipei City
    • Taipei, Taipei City, Taiwan, 10630
      • Cathay General Hospitla

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Age ≥ 20 years.
2. Familiarity with both cycling and treadmill exercise.
3. Negative response on the Physical Activity Readiness Questionnaire (PAR-Q).

Exclusion Criteria:

1. History of cardiovascular, pulmonary, or metabolic disease.
2. Musculoskeletal injuries limiting exercise range of motion.
3. Use of medications known to affect heart rate or ventilation.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cycling-First Sequence; Participants in this arm are randomized to perform the continuous ramp cardiopulmonary exercise testing (CPET) on a cycle ergometer first. After a washout period of 7 to 14 days, they cross over to perform the standardized treadmill ramp testing.	Device: Cycle Ergometer CPET; Following a 3-minute unloaded warm-up (0 W), continuous ramp increases began at 20 W/min for men or 15 W/min for women, targeting an 8-12 minute test duration to volitional exhaustion.; Device: Motorized Treadmill CPET (Porszász Protocol); Standardized ramp testing utilizing the Porszász algorithm. Simultaneous adjustments to speed and grade mathematically produce a linear rise in metabolic demand (matched to 20 or 15 W/min based on sex), ensuring identical oxygen uptake kinetic demands to the cycling protocol.
Experimental: Treadmill-First Sequence; Participants in this arm are randomized to perform the standardized treadmill ramp cardiopulmonary exercise testing (CPET) using the Porszász algorithm first. After a washout period of 7 to 14 days, they cross over to perform the cycle ergometer ramp testing.	Device: Cycle Ergometer CPET; Following a 3-minute unloaded warm-up (0 W), continuous ramp increases began at 20 W/min for men or 15 W/min for women, targeting an 8-12 minute test duration to volitional exhaustion.; Device: Motorized Treadmill CPET (Porszász Protocol); Standardized ramp testing utilizing the Porszász algorithm. Simultaneous adjustments to speed and grade mathematically produce a linear rise in metabolic demand (matched to 20 or 15 W/min based on sex), ensuring identical oxygen uptake kinetic demands to the cycling protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Modality-Specific Heart Rate Differences at Ventilatory Thresholds (VT1 and VT2)	The absolute difference in heart rate (measured in beats per minute, bpm) recorded at the first ventilatory threshold (VT1) and second ventilatory threshold (VT2) between cycle ergometry and treadmill running.	Identified during each 8 to 12-minute cardiopulmonary exercise test session (Sessions separated by 7 to 14 days).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Oxygen Consumption (VO2) at Thresholds and Peak	Absolute and relative oxygen consumption (mL/kg/min) at VT1, VT2, and peak exercise.	Extracted as 30-second averages centered on the threshold time points and peak during each exercise test session.
Ventilatory Equivalent for Carbon Dioxide (EqCO2)	VE/VCO2 ratio at VT1 and VT2 to assess cross-modal reliability.	immediately after exercise test
Oxygen Pulse (O2 pulse)	Calculated as VO2 divided by heart rate (mL/beat) at VT1 and VT2 to evaluate stroke volume and tissue extraction markers across modalities.	immediately after exercise test

Collaborators and Investigators

• Sponsor: Cathay General Hospital

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2024
• Primary Completion (Actual): November 30, 2024
• Study Completion (Actual): November 30, 2024

Study Registration Dates

• First Submitted: July 14, 2026
• First Submitted That Met QC Criteria: July 17, 2026
• First Posted (Actual): July 22, 2026

Study Record Updates

• Last Update Posted (Actual): July 22, 2026
• Last Update Submitted That Met QC Criteria: July 17, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Heart Rate; Cardiorespiratory Fitness; Exercise Intensity; Ventilatory Thresholds; Randomized Crossover Trial
• Additional Relevant MeSH Terms: Behavior; Motor Activity
• Other Study ID Numbers: 202311036RIND

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: The de-identified individual participant data that underlie the results reported in this article will be available to other researchers who provide a methodologically sound proposal. Proposals may be submitted to the corresponding author twdoggy@yahoo.com.tw for review. Data access will be granted upon signature of a data access agreement and ethical approval.
• IPD Sharing Time Frame: The data and supporting documents will be available immediately following the publication of the article and will remain available for 5 years after publication.
• IPD Sharing Access Criteria: Researchers interested in accessing the IPD or supporting documentation must submit a methodologically sound research proposal to the corresponding author for review. The proposal should clearly state the research question and the intended use of the data. Access to the de-identified data will be granted to researchers who meet the criteria after signing a data access agreement and demonstrating institutional ethical approval. Requests will be evaluated on a case-by-case basis to ensure participant privacy and data security.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No