Metabolic demands of a simulated smoke-diving drill.

The main goal of this study was to update the Finnish smoke-diving drill (FSDD) and to measure the physical strain of and recovery from the drill. Furthermore, the aim was to compare the physical strain of contract and professional firefighters and effect of floor materials. The associations between aerobic capacity and physical strain were also studied. The updates made included an added hose pull task and updating the equipment used. Heart rate (HR), oxygen consumption (V̇O2), and blood lactate concentration ([La-]) of 32 professional and 5 contract firefighters were measured before, during, and 10 and 30 min after the updated drill. The mean HR during the drill was 78% and V̇O2 59% of maximum. HR and [La-] had not recovered to baseline levels after 30-minute recovery period. Physical strain was higher among contract firefighters and [La-] accumulation on rough floor surfaces. Better aerobic capacity was associated with reduced physical strain.

The purpose of this study was to update the Finnish smoke-diving drill. This paper describes the process of updating the drill, and the experimental measurements regarding the metabolic demands of the updated drill. The updates made included adding a hose pull task and updating the equipment used during the drill.

Interventions to enhance recovery in healthy workers; a scoping review.

BACKGROUND: Faster recovery from work may help to prevent work-related ill health. AIMS: To provide a preliminary assessment of the range and nature of interventions that aim to improve recovery from cognitive and physical work. METHODS: A scoping review to examine the range and nature of the evidence, to identify gaps in the evidence base and to provide input for systematic reviews. We searched for workplace intervention studies that aimed at enhancing recovery. We used an iterative method common in qualitative research to obtain an overview of study elements, including intervention content, design, theory, measurements, effects and cost-effectiveness. RESULTS: We found 28 studies evaluating seven types of interventions mostly using a randomized controlled study design. For person-directed interventions, we found relaxation techniques, training of recovery experiences, promotion of physical activity and stress management. For work-directed interventions, there were participatory changes, work-break schedules and task variation. Most interventions were based on the conservation of resources and affect-regulation theories, none were based on the effort-recovery theory. The need for recovery (NfR) and the recovery experiences questionnaires (REQ) were used most often. Study authors reported a beneficial effect of the intervention in 14 of 26 published studies. None of the studies that used the NfR scale found a beneficial effect, whereas studies that used the REQ showed beneficial effects. Three studies indicated that interventions were not cost-effective. CONCLUSIONS: Feasible and possibly effective interventions are available for improving recovery from cognitive and physical workload. Systematic reviews are needed to determine their effectiveness.

Association of cardio-ankle vascular index with physical fitness and cognitive symptoms in aging Finnish firefighters.

PURPOSE: Monitoring cardiovascular risk factors is important in health promotion among firefighters. The assessment of arterial stiffness (AS) may help to detect early signs of atherosclerosis. The aim of this study was to analyze associations between aerobic fitness, cognitive symptoms and cardio-ankle vascular index (CAVI) as a measure for AS among Finnish firefighters. METHODS: The data are one part of a large 13-year follow-up study of the health and physical and mental capacity of Finnish professional firefighters. The subjects in this substudy comprised 65 male firefighters of a mean age of 48.0 (42-58) years in 2009. Their maximal oxygen uptake was successfully measured in two cross-sectional studies in 1996 and 2009, and they responded to questionnaires at both sessions, and their CAVI was measured in 2009. CAVI was calculated from the pulse waveform signal and pulse wave velocity. The lifestyle habits and subjective cognitive stress-related symptoms were collected via a standardized questionnaire. Muscular fitness was measured by the routine test battery used for Finnish firefighters. RESULTS: CAVI was related to age. About one-fifth of the firefighters had a CAVI of >8. Aerobic fitness was the main physiological factor correlating with increased CAVI. Interestingly, VO(2)max and the accelerated decrease in VO(2)max during a 13-year follow-up were associated with signs of impaired vascular function. The cognitive symptoms derived from the Profile of Mood States questionnaire (POMS) were mainly associated with stress and sleeping difficulties. No clear association with physical fitness was found in this population of fit firefighters. CONCLUSIONS: Among firefighters, the decrease in aerobic fitness predicts increased arterial stiffness. The speed of the age-related decline in maximal oxygen consumption is as important as absolute level. Against expectations, the cognitive function did not correlate with vascular health parameters. The cognitive symptoms, however, were only mild.

A novel treatment of cystic fibrosis acting on-target: cysteamine plus epigallocatechin gallate for the autophagy-dependent rescue of class II-mutated CFTR.

This corrects the article DOI: 10.1038/cdd.2016.22.

Transferrin-Targeted Nanoparticles Containing Zoledronic Acid as a Potential Tool to Inhibit Glioblastoma Growth.

The treatment of glioblastoma (GBM) is a challenge for the biomedical research since cures remain elusive. Its current therapy, consisted on surgery, radiotherapy, and concomitant chemotherapy with temozolomide (TMZ), is often uneffective. Here, we proposed the use of zoledronic acid (ZOL) as a potential agent for the treatment of GBM. Our group previously developed self-assembling nanoparticles, also named PLCaPZ NPs, to use ZOL in the treatment of prostate cancer. Here, we updated the previously developed nanoparticles (NPs) by designing transferrin (Tf)-targeted self-assembling NPs, also named Tf-PLCaPZ NPs, to use ZOL in the treatment of brain tumors, e.g., GBM. The efficacy of Tf-PLCaPZ NPs was evaluated in different GBM cell lines and in an animal model of GBM, in comparison with PLCaPZ NPs and free ZOL. Tf-PLCaPZ NPs were characterized by a narrow size distribution and a high incorporation efficiency of ZOL. Moreover, the presence of Tf significantly reduced the hemolytic activity of the formulation. In vitro, in LN229 cells, a significant uptake and cell growth inhibition after treatment with Tf-PLCaPZ NPs was achieved. Moreover, the sequential therapy of TMZ and Tf-PLCaPZ NPs lead to a superior therapeutic activity compared to their single administration. The results obtained in mice xenografted with U373MG, revealed a significant anticancer activity of Tf-PLCaPZ NPs, while the tumors remained unaffected with free TMZ. These promising results introduce a novel type of easy-to-obtain NPs for the delivery of ZOL in the treatment of GBM tumors.

A novel treatment of cystic fibrosis acting on-target: cysteamine plus epigallocatechin gallate for the autophagy-dependent rescue of class II-mutated CFTR.

We previously reported that the combination of two safe proteostasis regulators, cysteamine and epigallocatechin gallate (EGCG), can be used to improve deficient expression of the cystic fibrosis transmembrane conductance regulator (CFTR) in patients homozygous for the CFTR Phe508del mutation. Here we provide the proof-of-concept that this combination treatment restored CFTR function and reduced lung inflammation (P<0.001) in Phe508del/Phe508del or Phe508del/null-Cftr (but not in Cftr-null mice), provided that such mice were autophagy-competent. Primary nasal cells from patients bearing different class II CFTR mutations, either in homozygous or compound heterozygous form, responded to the treatment in vitro. We assessed individual responses to cysteamine plus EGCG in a single-centre, open-label phase-2 trial. The combination treatment decreased sweat chloride from baseline, increased both CFTR protein and function in nasal cells, restored autophagy in such cells, decreased CXCL8 and TNF-α in the sputum, and tended to improve respiratory function. These positive effects were particularly strong in patients carrying Phe508del CFTR mutations in homozygosity or heterozygosity. However, a fraction of patients bearing other CFTR mutations failed to respond to therapy. Importantly, the same patients whose primary nasal brushed cells did not respond to cysteamine plus EGCG in vitro also exhibited deficient therapeutic responses in vivo. Altogether, these results suggest that the combination treatment of cysteamine plus EGCG acts 'on-target' because it can only rescue CFTR function when autophagy is functional (in mice) and improves CFTR function when a rescuable protein is expressed (in mice and men). These results should spur the further clinical development of the combination treatment.

Degradation of low density lipoprotein cholesterol esters by lysosomal lipase in vitro. Effect of core physical state and basis of species selectivity.

The effect of the physical state of low density lipoprotein (LDL) core and the selectivity of the degradation of LDL cholesterol esters (CEs) by the lysosomal acid lipase (LAL) in vitro were investigated. The physical state of LDL was modulated by varying temperature or the triglyceride content of the core. Normal LDL showed an abrupt increase of CE hydrolysis at 24 degrees C and another deviation occurred close to 36 degrees C. 1H-NMR measurements showed that these temperatures coincide with the onset and end temperatures of the LDL core lipid transition, respectively. Enrichment of LDL with triglycerides abolished the abrupt changes both in the CE hydrolysis and in the physical state of LDL lipids. These findings show that there is a correlation between the physical state of LDL lipids and the rate of LAL-mediated hydrolysis of the CEs in the particle. The relative rates of hydrolysis of different CE species were also compared. With native LDL, increasing the length of a saturated acyl chain from 14 to 20 carbons reduced the rate of degradation of CE modestly, while increasing acyl chain unsaturation increased the rate of degradation markedly. However, cholesterol oleate was hydrolyzed more slowly than cholesterol stearate. Essentially the same order of hydrolytic susceptibility was observed when the CE species were incorporated into triglyceride-enriched LDL, reconstituted high density lipoprotein particles or in detergent/phospholipid micelles. These results indicate that the selective hydrolysis of CE species in LDL is determined mainly by the ease with which the CE molecule can emerge from the surface layer reach the active site of LAL. Slower degradation of the more saturated CEs by LAL could lead, under certain conditions, to their accumulation in lysosomes and eventually, to cell death, lysis and deposition of crystalline, poorly mobilizable lipids to the arterial intima.

Elongation of both branches of biantennary backbones of oligo-(N-acetyllactosamino)glycans by human serum (1----3)-N-acetyl-beta-D- glucosaminyltransferase.

Partial reactions catalyzed by a (1----3)-N-acetyl-beta-D- glucosaminyltransferase (EC2.4.1.149), known to be present in human serum, were studied by use of biantennary "backbone" saccharides of oligo-N-acetyllactosamine-type as acceptors. Incubation of the radiolabeled blood-group I-active hexasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp- (1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-GlcNAc (1) and UDP-GlcNAc with serum gave first a transient 1:1 mixture of two isomeric heptasaccharides, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D- GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D- Galp-(1----4)-D-GlcNAc (2) and beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-GlcpNAc-(1----3)- beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-Glc NAc (3), showing that both branches of 1 react equally well. The two heptasaccharides reacted further in the incubation mixture to form the radiolabeled octasaccharide, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[be ta-D- GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Ga lp- (1----4)-D-GlcNAc (4); during this second reaction, the composition of the heptasaccharide mixture remained unchanged, indicating that 2 and 3 reacted at approximately equal rates. The heptasaccharides 2 and 3 could not be separated from each other, but they could be detected, identified, and quantitatively determined by stepwise enzymic degradations. Partial (1----3)-N-acetyl-beta-D-glucosaminylation reactions, carried out with another acceptor, the branched pentasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta- D- GlcpNAc-(1----6)]-beta-D-Gal (11), revealed that it reacted also equally well at both branches.(ABSTRACT TRUNCATED AT 400 WORDS)

Physical work load, fetal development and course of pregnancy.

The effects of physical work load during pregnancy were analyzed in connection with a nationwide case-referent study that screened for associations between selected structural malformations and occupational exposures. The strain of the occupational activities of 1475 mothers of malformed infants and an equal number of mothers of noncase babies was assessed from a description of the work tasks by an expert using a standardized method reflecting energy expenditure. The noncase mothers' experience revealed a relation between physical load and growth retardation that has also been suggested by other epidemiologic studies. No relation was found between an increase in mean physical load and the occurrence of threatened abortion; yet work involving much standing had an increased risk. Mothers whose work included occasional high physical loads had more pregnancy-induced hypertension. The data showed unexpected associations between physical load and structural malformations.

The effect of appraisers in estimating metabolic rate with the Edholm scale.

A study was made of the appraisers' effect on the estimation of metabolic rate with the Edholm scale and a table of the ISO 7243 heat stress standard. The appraisers, five experienced and five inexperienced persons, estimated the metabolic rate of three different work tasks from videotapes. Analysis of variance indicated significant ( [Formula: see text] ) differences in the appraisers' recordings of the activities. The appraisers were grouped according to the similarity of the estimated values they gave. The groups thus contained both experienced and inexperienced appraisers, and it was not possible to classify the appraisers into experienced and inexperienced groups according to their earlier experience. The metabolic rates according to the Edholm scale were higher than according to the ISO 7243 table. The differences in metabolic rates given by the individual observers varied from 38 to 118 W/m(2). The variations in the estimation of metabolic rates were greater when the Edholm scale was used. This variation caused considerable variation also in the predicted mean vote, PMV index. It is recommended that the appraisers be selected carefully, because it is not possible to know whether a randomly selected appraiser is an 'average' or an 'extreme' appraiser without a test. Before conducting extensive field surveys where several appraisers estimate the metabolic rates, it would be useful to arrange training in order to calibrate the levels of the Edholm scale as well as ISO method among the appraisers because training clearly unified the estimation.

Caveolins and membrane cholesterol.

Caveolae (small plasma membrane invaginations) and their coat proteins, caveolins, have attracted the attention of researchers in diverse fields, including cell biology, cardiovascular and cancer research. The tight association between caveolin and cholesterol governs the biochemical behaviour of caveolae and is emerging as an important characteristic in a number of processes assigned to these multifunctional organelles. In this review, selected aspects of the caveolin-cholesterol association and its potential functional implications are discussed.

Are the job demands on physical work capacity equal for young and aging firefighters?

The job demands on physical work capacity and the frequency of the firefighting and rescue tasks were rated by 156 professional firefighters (age range, 22 to 54 years) who responded to a questionnaire. Smoke-diving requiring the use of personal protective equipment was considered to demand most aerobic power. The clearing of debris with heavy manual tools, and roof work set the highest demands on muscular performance and motor coordination, respectively. During the past 5 years, 83 to 88% of the respondents had performed these tasks on average four times a year. The rating and frequency of the tasks were not significantly affected by age. The results suggest that the job demands on physical work capacity remain the same throughout the occupational career of the firefighters.

Fate of the 6K membrane protein of Semliki Forest virus during virus assembly.

The Semliki Forest virus directs the synthesis of three virus-specific transmembrane proteins p62, 6K, and E1, which all are made in equimolar amounts from a polyprotein precursor molecule. The p62 and E1 spike proteins form heterodimeric complexes in the endoplasmic reticulum before being transported to the cell surface where virus budding occurs. In this study we show that the 6K protein becomes associated to the p62E1 complex in the endoplasmic reticulum and transported with the complex to the cell surface. During virus budding, E1 and p62 (which has matured into the E2 protein) are incorporated into new virions whereas the 6K is mostly excluded. Virus particles released from infected BHK cells contain only about 3% of 6K in their membrane as compared to the spike protein content. The relevance of these findings for the mechanism of SFV assembly is discussed.

In vitro mutagenesis of a full-length cDNA clone of Semliki Forest virus: the small 6,000-molecular-weight membrane protein modulates virus release.

We report on the construction of a full-length cDNA clone of Semliki Forest virus (SFV). By placing the cDNA under the SP6 promoter, infectious RNA can be produced in vitro and used to transfect cells to initiate virus infection. To achieve efficient transfections, a new protocol for electroporation of RNA was developed. This method gave up to 500-fold improvement over the traditional DEAE-dextran transfection procedure. Since virtually 100% of the cells can be transfected by electroporation, this method is a useful tool for detailed biochemical studies of null mutations of SFV that abolish production of infections virus particles. We used the cDNA clone of SFV to study what effects a deletion of the 6,000-molecular-weight membrane protein (6K membrane protein) had on virus replication. The small 6K protein is part of the structural precursor molecule (C-p62-6K-E1) of the virus. Our results conclusively show that the 6K protein is not needed for the heterodimerization of the p62 and E1 spike membrane proteins in the endoplasmic reticulum, nor is it needed for their transport out to the cell surface. The absence of the 6K protein did, however, result in a dramatic reduction in virus release, suggesting that the protein exerts its function late in the assembly pathway, possibly during virus budding.

Direct observation of lipoprotein cholesterol ester degradation in lysosomes.

We have investigated whether pyrene-labelled cholesterol esters (PyrnCEs) (n indicates the number of aliphatic carbons in the pyrene-chain) can be used to observe the degradation of low-density lipoprotein (LDL)-derived cholesterol esters (CEs) in the lysosomes of living cells. To select the optimal substrates, hydrolysis of the PyrnCE species by lysosomal acid lipase (LAL) in detergent/phospholipid micelles was compared. The rate of hydrolysis varied markedly depending on the length of the pyrenyl chain. Pyr10CE was clearly the best substrate, while Pyr4CE was practically unhydrolysed. Pyr10CE and [3H]cholesteryl linoleate, the major CE species in LDL, were hydrolysed equally by LAL when incorporated together into reconstituted LDL (rLDL) particles, thus indicating that Pyr10CE is a reliable reporter of the lysosomal degradation of native CEs. When rLDL particles containing Pyr4CE or Pyr10CE were incubated with fibroblasts, the accumulation of bright intracellular vesicular fluorescence was observed with the former fluorescent derivative, but not with the latter. However, when the cells were treated with chloroquine, an inhibitor of lysosomal hydrolysis, or when cells with defective LAL were employed, Pyr10CE also accumulated in vesicular structures. HPLC analysis of cellular lipid extracts fully supported these imaging results. It is concluded that PyrnCEs can be used to observe degradation of CEs directly in living cells. This should be particularly useful when exploring the mechanisms responsible for the accumulation of lipoprotein-derived CEs in complex systems such as the arterial intima.

Human serum contains a novel beta 1,6-N-acetylglucosaminyltransferase activity that is involved in midchain branching of oligo (N-acetyllactosaminoglycans).

Incubation of UDP-GlcNAc and radiolabeled GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc (1) with human serum resulted in the formation of the branched hexasaccharide GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4GlcNAc (2) in yields of up to 22.2%. The novel reaction represents midchain branching of the linear acceptor; the previously known branching reactions of oligo-(N-acetyllactosaminoglycans) involve the nonreducing end of the growing saccharide chains. The structure of 2 was established by use of appropriate isotopic isomers of it for degradative experiments. The hexasaccharide 2 was cleaved by an exhaustive treatment with jack bean beta-N-acetylhexosaminidase, liberating two GlcNAc units and the tetrasaccharide Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc (3). Endo-beta-galactosidase from Bacteroides fragilis cleaved 2 at one site only, yielding the disaccharide GlcNAc beta 1-3Gal (4) and the branched tetrasaccharide GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4GlcNAc (5). The structure of 5 was established by partial acid hydrolysis and subsequent identification of the disaccharide GlcNAc beta 1-6Gal (6), together with the trisaccharides GlcNAc beta 1-6Gal beta 1-4GlcNAc (7) and GlcNAc beta 1-3(GlcNAc beta 1-6)Gal (8) among the cleavage products. Galactosylation of 2 with bovine milk beta 1,4-galactosyltransferase and UDP-[6-3H]Gal gave the octasaccharide [6-3H]Gal beta 1-4GlcNAc beta 1-3 Gal beta 1-4GlcNAc beta 1-3([6-3H]-Gal beta 1-4GlcNAc beta 1-6)[U-14C] Gal beta 1-4GlcNAc (17), which could be cleaved with endo-beta-galactosidase into the trisaccharide [6-3H]Gal beta 1-4GlcNAc beta 1-3Gal (18) and the branched pentasaccharide GlcNAc beta 1-3-([6-3H]Gal beta 1-4GlcNAc beta 1-6) [U-14C]Gal beta 1-4GlcNAc (19). Partial hydrolysis of 2 with jack-bean beta-N-acetylhexosaminidase gave the linear pentasaccharide 1 and the branched pentasaccharide Gal beta 1-4GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4GlcNAc (20). The serum beta 1,6-GlcNAc transferase catalyzed also the formation of GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4Glc (11) from UDP-GlcNAc and GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc (10). The pentasaccharide Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc (16), too, served as an acceptor for the enzyme.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical evaluation of heavy tool-handling in two age groups of firemen.

The biomechanical load of a rescue-clearing task (lifting a power saw from the floor up to the ceiling level) was evaluated with six older (47 +/- 5 years) and seven younger firemen (32 +/- 2 years). The mean dynamic compressive force at the L5/SI disc was 5998 N for the older subjects and 6392 N for the younger subjects. The peak torques for the back and knee extensions were about equal for the two groups of the subjects. The younger subjects had a significantly higher movement speed in the knee extension than the older subjects (89.1 +/- 25.7 vs. 35.3 +/- 11.5 degrees/s, p less than 0.001). The results showed that lifting a power saw produced a high load on the musculoskeletal system, and that the load was not influenced by age.

The mechanism of human plasma phospholipid transfer protein-induced enlargement of high-density lipoprotein particles: evidence for particle fusion.

1. Phospholipid transfer protein (PLTP) mediates conversion of high-density lipoprotein (HDL3) to large particles, with concomitant release of apolipoprotein A-I (apoA-I). To study the mechanisms involved in this conversion, reconstituted HDL (rHDL) particles containing either fluorescent pyrenylacyl cholesterol ester (PyrCE) in their core (PyrCE-rHDL) or pyrenylacyl phosphatidylcholine (PysPC) in their surface lipid layer (PyrPC-rHDL) were prepared. Upon incubation with PLTP they behaved as native HDL3, in that their size increased considerably. 2. When PyrPC-rHDL was incubated with HDL3 in the presence of PLTP, a rapid decline of the pyrene excimer/monomer fluorescence ratio (E/M) occurred, demonstrating that PLTP induced mixing of the surface lipids of PyrPC-rHDL and HDL3. As this mixing was almost complete before any significant increase in HDL particle size was observed, it represents PLTP-mediated phospholipid transfer or exchange that is not directly coupled to the formation of large HDL particles. 3. When core-labelled PyrCE-rHDL was incubated in the presence of PLTP, a much slower, time-dependent decrease of E/M was observed, demonstrating that PLTP also promotes mixing of the core lipids. The rate and extent of mixing of core lipids correlated with the amount of PLTP added and with the increase in particle size. The enlarged particles formed could be visualized as discrete, non-aggregated particles by electron microscopy. Concomitantly with the appearance of enlarged particles, lipid-poor apoA-I molecules were released. These data, together with the fact that PLTP has been shown not to mediate transfer of cholesterol esters, strongly suggest that particle fusion rather than (net) lipid transfer or particle aggregation is responsible for the enlargement of HDL particles observed upon incubation with PLTP.4.ApoA-I rHDL, but not apoA-II rHDL, were converted into large particles, suggesting that the presence of apoA-I is required for PLTP-mediated HDL fusion. A model for PLTP-mediated enlargement of HDL particles is presented.

Physiological responses of firefighting students during simulated smoke-diving in the heat.

While wearing a self-contained breathing apparatus and fire-protective clothing, 35 healthy firefighting students aged 19-27 years performed smoke-diving (entry into a smoke-filled room) during a simulated shipboard fire. The mean (+/- SD) ambient temperature inside the simulator was 119 +/- 12 degrees C, and the task lasted 17 +/- 4 min. All subjects were fit according to their maximal oxygen consumption, which was 52.4 +/- 5.2 mL/min/kg (4.08 +/- 0.45 l/min). During the smoke-diving the average heart rate was 150 +/- 13 beats/min (79 +/- 6% of maximal heart rate attained in a cycle-ergometer test), and the peak heart rate was 180 +/- 13 beats/min (95 +/- 6% of maximal heart rate). The estimated oxygen consumption was 2.4 +/- 0.5 L/min (60 +/- 12% of maximal oxygen consumption). Neither ability to tolerate stress (as determined by the instructors) nor previous experience in smoke-diving tasks seemed to influence the heart rate or estimated oxygen consumption during experiment. Smoke-diving was physically very demanding even for the young and fit subjects, showing the importance of regular evaluation of the health and physical fitness of every firefighter who has to carry out smoke-diving tasks.