Reproducibility of cardiorespiratory and cellular responses to steady state exercise in hypoxia and preloaded cycling time trial performance reliability in normoxia and acute hypoxia
- Published
- Accepted
- Subject Areas
- Biochemistry, Anatomy and Physiology
- Keywords
- Hypoxia, Exercise, heat shock protein 70, time trial performance, reproducibility
- Copyright
- © 2015 Lee et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ PrePrints) and either DOI or URL of the article must be cited.
- Cite this article
- 2015. Reproducibility of cardiorespiratory and cellular responses to steady state exercise in hypoxia and preloaded cycling time trial performance reliability in normoxia and acute hypoxia. PeerJ PrePrints 3:e1513v1 https://doi.org/10.7287/peerj.preprints.1513v1
Abstract
Background. The purpose of this study was to assess the reproducibility of cardiorespiratory and cellular (monocyte heat shock protein 70; mHSP70) responses to a fixed load hypoxic stress test (HST) and the reliability of a pre-loaded 16.1km cycling time trial (pTT) conducted under both normoxic and hypoxic conditions. Methods. Eighteen participants (age, 22 ± 4 years; height, 1.77 ± 0.04 meters; body mass, 76.8 kg; estimated body fat and VO2peak = 3.50 ± 0.60 L.min-1) were divided into three groups. Reliability of responses (HR, SPO2, VO2, VCO2, VE and RER) to the HST (FIO2 0.14; 15 minutes rest, 60 minutes cycling at 50% normoxic VO2peak) was assessed across 3 repeat trials (HST 1, 2 and 3, n = 6); mHSP70 was measured via flow cytometry before and after each HST (n = 5); resting HSP was also quantified on 4 separate occasions (n=5). Reliability of the pTT (15 min rest, 40 minutes cycling at 50% normoxic VO2peak) was assessed across 3 repeat normoxic (N; FIO2 ≈ 0.21; n=6) and 3 repeat hypoxic (FIO2 ≈ 0.14; n = 6) trials. All exercise trials were undertaken at the same time of day, following exercise and dietary controls, 7 days apart. Results. Intra-class correlation coefficients (ICC’s) for mean and peak HR, SpO2, VE , VO2 , VCO2 and BLa within each trial were improved from HST1 to HST2 (mean data: 0.99, 0.95, 0.75, 0.62, 0.70, 0.90; peak data: 0.98, 0.96, 0.64, 0.69, 0.74, 0.75) to HST2 and HST3 (ICC = 0.99, 0.97, 0.82, 0.85, 0.87 and 0.96 respectively). mHSP70 was a reproducible at rest without (ICC > 0.95) and with HSTs conducted in the previous 7 days (ICC > 0.95), with no difference in pre to post increases in mHSP70 observed between tests. The reliability for time to pTT completion was improved following one trial, and the CV (test 2 vs. 3) was similar under normoxic (CV = 0.62) and hypoxic conditions (CV = 0.63). Conclusion. Cardiorespiratory and cellular responses to the HST were reproducible and the pTT performance time reliable in both N and H. Since the reproducibility of the measurements in HST trials and reliability of pTT improved between the second and third trials one familiarization visit is recommended prior to employing these protocols in future studies.
Author Comment
This article describes a reproducible method for determining cardiovascular and cellular responses to exercise under conditions of acute normobaric hypoxia in recreationally active males. This article will be submitted to PeerJ for peer review.
Supplemental Information
Table 1
Measures of reliability for mean exercise and peak physiological variables during the HST (n = 6).
Table 2
Measures of reliability for mHSP70 (MFI A.U) for 5 repeated resting measurements (n = 5), prior to and after each HST (n = 6).
Table 3
Measures of reliability in normoxic (n = 6) and hypoxic (n = 6) conditions during the time trial. Data are calculated from the mean TT power output (Watts) and heart rate.
Figure 1: A typical flow cytometry file following staining with mHSP70 positive and negative antibodies
A typical flow cytometry profile showing a) forward side scatter (FSC-H/SSC-H) with gated monocytes and b) florescence intensity (FL1-H nm; FITC stained samples on a linear scale) of monocytes incubated with isotype matched negative controls (black line) and anti-HSP70 (green line) antibodies
Figure 2: Cardiorespiratory responses to the repeated hypoxic tests
Mean ± SD heart rate and SpO2 (a), VE (b), VO2 (c), and VCO2 (d) during the 3 HST’s (n = 6). No differences were observed across trials (p > 0.05).
Figure 3: mHSP70 responses to hypoxic exercise
Microsoft Word - Lee_Thake_reliability_hypoxia_2015.docx Repeat measurements of Monocyte HSP70 (n = 5) without (a) and with (b; n = 5) a HST in the previous 7 days. Panel c illustrates the reliable inverse response after exercise mHSP70 has with resting mHSP70. Lines show individual data and the bars represent the group mean.
Figure 4. Performance time and physiological data during repeated normoxic and hypoxic time trials
Mean ± SD performance time, average power output at each km, and average HR for each km in both the NORM (n = 6, panel a, b, c) and HYP (n = 6, panel d, e, f) throughout the 16.1 km time trial.