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Okawara H, Iwasawa Y, Sawada T, Sugai K, Daigo K, Seki Y, Ichihara G, Nakashima D, Sano M, Nakamura M, Sato K, Fukuda K, Katsumata Y. Anaerobic threshold using sweat lactate sensor under hypoxia. Sci Rep 2023; 13:22865. [PMID: 38129473 PMCID: PMC10739691 DOI: 10.1038/s41598-023-49369-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 12/07/2023] [Indexed: 12/23/2023] Open
Abstract
We aimed to investigate the reliability and validity of sweat lactate threshold (sLT) measurement based on the real-time monitoring of the transition in sweat lactate levels (sLA) under hypoxic exercise. In this cross-sectional study, 20 healthy participants who underwent exercise tests using respiratory gas analysis under hypoxia (fraction of inspired oxygen [FiO2], 15.4 ± 0.8%) in addition to normoxia (FiO2, 20.9%) were included; we simultaneously monitored sLA transition using a wearable lactate sensor. The initial significant elevation in sLA over the baseline was defined as sLT. Under hypoxia, real-time dynamic changes in sLA were successfully visualized, including a rapid, continual rise until volitionary exhaustion and a progressive reduction in the recovery phase. High intra- and inter-evaluator reliability was demonstrated for sLT's repeat determinations (0.782 [0.607-0.898] and 0.933 [0.841-0.973]) as intraclass correlation coefficients [95% confidence interval]. sLT correlated with ventilatory threshold (VT) (r = 0.70, p < 0.01). A strong agreement was found in the Bland-Altman plot (mean difference/mean average time: - 15.5/550.8 s) under hypoxia. Our wearable device enabled continuous and real-time lactate assessment in sweat under hypoxic conditions in healthy participants with high reliability and validity, providing additional information to detect anaerobic thresholds in hypoxic conditions.
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Affiliation(s)
- Hiroki Okawara
- Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Yuji Iwasawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tomonori Sawada
- Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Kazuhisa Sugai
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Kyohei Daigo
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yuta Seki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Genki Ichihara
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Daisuke Nakashima
- Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Motoaki Sano
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Masaya Nakamura
- Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Kazuki Sato
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yoshinori Katsumata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan.
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Muramoto Y, Nakashima D, Amano T, Harita T, Sugai K, Daigo K, Iwasawa Y, Ichihara G, Okawara H, Sawada T, Kinoda A, Yamada Y, Kimura T, Sato K, Katsumata Y. Estimation of maximal lactate steady state using the sweat lactate sensor. Sci Rep 2023; 13:10366. [PMID: 37365235 DOI: 10.1038/s41598-023-36983-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 06/13/2023] [Indexed: 06/28/2023] Open
Abstract
A simple, non-invasive algorithm for maximal lactate steady state (MLSS) assessment has not been developed. We examined whether MLSS can be estimated from the sweat lactate threshold (sLT) using a novel sweat lactate sensor for healthy adults, with consideration of their exercise habits. Fifteen adults representing diverse fitness levels were recruited. Participants with/without exercise habits were defined as trained/untrained, respectively. Constant-load testing for 30 min at 110%, 115%, 120%, and 125% of sLT intensity was performed to determine MLSS. The tissue oxygenation index (TOI) of the thigh was also monitored. MLSS was not fully estimated from sLT, with 110%, 115%, 120%, and 125% of sLT in one, four, three, and seven participants, respectively. The MLSS based on sLT was higher in the trained group as compared to the untrained group. A total of 80% of trained participants had an MLSS of 120% or higher, while 75% of untrained participants had an MLSS of 115% or lower based on sLT. Furthermore, compared to untrained participants, trained participants continued constant-load exercise even if their TOI decreased below the resting baseline (P < 0.01). MLSS was successfully estimated using sLT, with 120% or more in trained participants and 115% or less in untrained participants. This suggests that trained individuals can continue exercising despite decreases in oxygen saturation in lower extremity skeletal muscles.
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Affiliation(s)
- Yuki Muramoto
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Daisuke Nakashima
- Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
| | | | | | - Kazuhisa Sugai
- School of Veterinary Nursing and Technology, Faculty of Veterinary Science, Nippon Veterinary and Life Science University, Tokyo, Japan
| | - Kyohei Daigo
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yuji Iwasawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Genki Ichihara
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Hiroki Okawara
- Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Tomonori Sawada
- Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Akira Kinoda
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Yuichi Yamada
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Takeshi Kimura
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Kazuki Sato
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Yoshinori Katsumata
- Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan.
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.
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