The First Lactate Threshold Is a Limit for Heavy Occupational Work

Fasching, Patrick; Rinnerhofer, Stefan; Wultsch, Georg; Birnbaumer, Philipp; Hofmann, Peter

doi:10.3390/jfmk5030066

“…At target intensities above P LTP2 , physiologic parameters have been shown to increase continuously from DTh1 until t max (Viru, 1995 ). At target intensities below P LTP1/VT1 , t max is considerably longer and, consequently, other limiting factors occur (Fasching et al, 2020 ; Pokan et al, 2014 ).…”

Section: Discussionmentioning

confidence: 99%

Exercise duration: Independent effects on acute physiologic responses and the need for an individualized prescription

Tschakert

¹

,

Handl

²

,

Weiner

³

et al. 2022

Physiological Reports

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An individualization of exercise prescription is implemented mainly in terms of intensity but not for duration. To survey the need for an individualized exercise duration prescription, we investigated acute physiologic responses during constant‐load exercise of maximal duration ( t max ) and determined so‐called duration thresholds. Differences between absolute (min) and relative terms (% t max ) of exercise duration were analyzed. Healthy young and trained male and female participants ( n = 11) performed an incremental exercise test and one t max constant‐load exercise test at a target intensity of 10% of maximal power output below the second lactate turn point (LTP 2 ). Blood lactate, heart rate, and spirometric data were measured during all tests. t max was markedly different across subjects (69.6 ± 14.8 min; range: 40–90 min). However, distinct duration phases separated by duration thresholds (DTh) were found in most measured variables. These duration thresholds (except DTh1) were significantly related to t max (DTh2: r 2 = 0.90, p < 0.0001; DTh3: r 2 = 0.98, p < 0.0001) and showed substantial interindividual differences if expressed in absolute terms (DTh2: 24.8 ± 6.0 min; DTh3: 47.4 ± 10.6 min) but not in relative terms (DTh2: 35.4 ± 2.7% t max ; DTh3: 67.9 ± 2.4% t max ). Our data showed that (1) maximal duration was individually different despite the same relative intensity, (2) duration thresholds that were related to t max could be determined in most measured variables, and (3) duration thresholds were comparable between subjects if expressed in relative terms. We therefore conclude that duration needs to be concerned as an independent variable of exercise prescription.

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“…VO 2 ) showed significantly lower values during uninterrupted work compared to . VO 2,C in our study, i.e., oxygen consumption only during the time with physical stress (T C ) [3,20]. These results suggest that bulk waste collection involves either higher peak workloads or higher total workloads compared to the aforementioned studies.…”

Section: Discussionmentioning

confidence: 43%

“…Another subgroup of waste collectors included in an investigation of a variety of occupations [20] showed a similar result with lower values for total . VO 2 and lower .…”

Section: Discussionmentioning

confidence: 72%

“…According to more recent publications, a maximum acceptable RAS of 33-40% . VO 2,max seems too low, since this value does not represent a physiologically reasonable limit in relation to thresholds such as the ventilatory threshold (VT1) or the lactate turning point 1 (LTP1) [3,[18][19][20]. The VT1 and LTP1 allow us to identify the individual turning point from aerobic to anaerobic metabolism and have therefore been proposed as indicators of heavy workload [20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

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Physical workload and cardiopulmonary parameters in relation to individual capacity of bulk waste workers – a cross-sectional field-study

Kraft,

Velasco Garrido,

Herold

et al. 2023

J Occup Med Toxicol

1

0

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Purpose Waste collection is considered particularly heavy work, although no previous study has yet investigated the strain of bulk waste collection. The aim of this study is to determine the workload of bulk waste workers in practice. Method We conducted a cross-sectional field-study. Fourteen male volunteers from the bulk waste collection of the municipal sanitation department in Hamburg, Germany, were included. Performance was determined by cardiopulmonary exercise testing under laboratory conditions. During the shift, each worker was accompanied by a researcher, and heart rate (HR) was recorded under field conditions using an HR watch with a belt system. We examined mean HR, relative heart rate (RHR), relative aerobic strain (RAS), calculated oxygen uptake ($$\mathrm{\overset{.}{V}O}_2$$ V . O 2 ) and individual ventilatory threshold 1 (VT1) as parameters of workload during their daily work. Results During the shift, HR was scaled: 102 bpm (SD 10.2), RHR: 36.9%, $$\mathrm{\overset{.}{V}O}_2$$ V . O 2 : 1267 ml/min (SD 161), RAS: 49.4% (SD 9.3), and $$\mathrm{\overset{.}{V}O}_2$$ V . O 2 in relation to VT1: 75% (SD 18.5). There was no significant difference between oxygen consumption during the main task of lifting and carrying bulky waste and the individual $$\mathrm{\overset{.}{V}O}_2$$ V . O 2 at VT1. Conclusion Although the burden of the main task of lifting and carrying bulky waste is very high (at VT1 for more than 3 h), interruptions from other tasks or formal breaks spread the burden over the entire shift. The total workload exceeded most recommendations in the literature across the different work periods. However, the total burden remains below VT1, the only parameter that takes individual endurance performance into account. We recommend again VT1 as an individual upper limit for prolonged occupational work.

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“…Even for a regular working population, individual differences might impose different risk levels when, for example, assessing the heat stress risk using the metabolic rate for the human average [26]. In addition, in ergonomic risk assessment, the evaluation of physical effort and work-rest cycles, the individual adjustments are crucial to prevent overexertion and musculoskeletal-related injuries [28,73].…”

Section: Energy Expenditure Estimation In the Occupational Contextmentioning

confidence: 99%

Modeling Energy Expenditure Estimation in Occupational Context by Actigraphy: A Multi Regression Mixed-Effects Model

Lucena

¹

,

Guedes

²

,

Vaz

³

et al. 2021

IJERPH

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The accurate prediction of energy requirements for healthy individuals has many useful applications. The occupational perspective has also been proven to be of great utility for improving workers’ ergonomics, safety, and health. This work proposes a statistical regression model based on actigraphy and personal characteristics to estimate energy expenditure and cross-validate the results with reference standardized methods. The model was developed by hierarchical mixed-effects regression modeling based on the multitask protocol data. Measurements combined actigraphy, indirect calorimetry, and other personal and lifestyle information from healthy individuals (n = 50) within the age of 29.8 ± 5 years old. Results showed a significant influence of the variables related to movements, heart rate and anthropometric variables of body composition for energy expenditure estimation. Overall, the proposed model showed good agreement with energy expenditure measured by indirect calorimetry and evidenced a better performance than the methods presented in the international guidelines for metabolic rate assessment proving to be a reliable alternative to normative guidelines. Furthermore, a statistically significant relationship was found between daily activity and energy expenditure, which raised the possibility of further studies including other variables, namely those related to the subject’s lifestyle.

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The First Lactate Threshold Is a Limit for Heavy Occupational Work

Cited by 7 publications

References 36 publications

Exercise duration: Independent effects on acute physiologic responses and the need for an individualized prescription

Exercise duration: Independent effects on acute physiologic responses and the need for an individualized prescription

Physical workload and cardiopulmonary parameters in relation to individual capacity of bulk waste workers – a cross-sectional field-study

Modeling Energy Expenditure Estimation in Occupational Context by Actigraphy: A Multi Regression Mixed-Effects Model

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