Veikko Louhevaara

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.

Prediction of acceptable physical work loads based on responses to prolonged arm and leg exercise

Nine healthy men (aged 54-59 years) performed arm crank and leg cycle exercises for 30 min at relative work loads of 50 and 75% of peak oxygen uptake (VO2) for the corresponding muscle group, and for 60 min at a relative work load of 30% of peak VO2 for the corresponding muscle group. In the tests, heart rate (HR), blood pressure, gas exchange variables, rating of perceived exertion (RPE) and blood lactate were measured. At the 75% target exercise level, four subjects interrupted the arm-cranking test, and one subject interrupted the leg-cycle test. Owing to differences in peak values during arm-cranking and leg-cycling, the work load and the VO2 were higher during leg-cycling than during arm-cranking. There was no difference in HR between the work modes, but the HR increased to a greater extent during arm-cranking compared to leg-cycling at the 30% (NS) and 50% (P < 0.05) exercise levels. Similarly, the RPE increased more during arm-cranking compared to leg-cycling at each exercise level. The blood lactate concentration was higher after arm-cranking than after leg-cycling; at the 50% exercise level the difference was statistically significant. The results indicate a higher physiological strain with time during arm exercise than during leg exercise at the same muscle group-specific relative work load. The acceptable physical work load, expressed as the percentage peak VO2 for the corresponding muscle group, should thus be lower during arm exercise than during leg exercise. The RPE and the relative HR, expressed as percentage of peak HR for the corresponding muscle group, however, seem to be comparable indicators for the physiological strain during arm and leg exercise.

Effects of Ergorest Arm Supports on Muscle Strain and Wrist Positions During the Use of the Mouse and Keyboard in Work With Visual Display Units: A Work Site Intervention

The effects of Ergorest® arm supports on wrist angles and musculoskeletal strain in the neck-shoulder-arm region and electrical activity in the shoulder and arm muscles were studied during typing or the use of the mouse in work with a visual display unit (VDU). Twenty-one women were randomized into 3 groups (1 arm support, 2 arm supports, and control). Measurements were carried out before and after the 6-week intervention. The wrist extension of the mouse hand, the muscle activity of the trapezius muscle, and the subjective discomfort ratings indicated that 2 arm supports were better than 1 in work with a mouse. The Ergorest® arm support alleviates muscle and joint strain in VDU work when used for both arms.

Maximal working times with a self-contained breathing apparatus

The effects of a self-contained breathing apparatus (SCBA, total weight of 15·5 kg) on relative aerobic strain (%[Vdot]O2max) and heart rate (HR) were studied at light, moderate, and heavy exercise levels on a treadmill in temperate conditions. The subjects comprised 13 firemen whose mean [Vdot]O2 max was 4·161 min−1 (range 2·85 to 5·331 min−1). Maximal working times (WTmax) with SCBA were calculated with the results for this study and with experimental data from the literature. The subjects %[Vdot]O2 max and HR increased significantly more with SCBA than in the control test without SCBA. This increase reduced the calculated WT max values. During moderately heavy exercise ([Vdot]O2control = 2·01 min−1), carrying SCBA increased the subjects %[Vdot]O2max from 48 to 69 and decreased their estimated WT max from over 60 to 44 min. The estimated WT max for a single operation with SCBA was critically short (18 min) when the average [Vdot]O2 max for men aged 20–29 (3·51 min−1) was used in the calculations. Ther...

Comparison of three field methods for measuring oxygen consumption

The Oxylog (OX) and the Kofranyi-Michaelis ( KM) field methods for measuring oxygen consumption ( [Vdot]O2) were compared with the conventional Douglas Bag (DB) technique in standardized walking and lifting work in the laboratory. Subjects comprised six men. According to the mean differences in [Vdot]O2 the OX underestimated ( 41% and 6.4% ) and the KM overestimated (3.8% and 0.8% ) [Vdot]O2in walking and lifting work, respectively. The linear regression equations between the DB and the OX as well as between the DB and the KM revealed a good agreement (r= 0.91-0.99) of the [Vdot]O2values. The OX and the KM are accurate for reliable [Vdot]O2measurements under field conditions. Some practical improvements for the OX use, based on several field studies, are recommended.

Cardiorespiratory strain during walking in snow with boots of differing weights

In order to assess the physiological strain of different boot weights, seven male and three female subjects walked on a treadmill and a snow-field while wearing three types of boots: winter jogging boots (WJB), rubber boots (RB), and rubber safety boots (RSB), weighing (means +/- s.d.) 0.9 +/- 0.1, 1.9 +/- 0.4 and 2.5 +/- 0.2 kg, respectively During each walk the subjects wore the same clothing ensembles and moved at the same, individually determined speed. The mean (+/- s.e.) depths of the footprint impression in the snow while walking in the WJB, RB, and RSB were 26.1 +/- 1.5, 25.6 +/- 1.4 and 26.1 +/- 1.5 cm (NS), respectively. During walking on the treadmill, the means for oxygen consumption were 0.79 +/- 0.05, 0.81 +/- 0.06 and 0.83 +/- 0.04 l min-1 (NS) and in snow 2.24 +/- 0.18, 2.34 +/- 0.17 and 2.34 +/- 0.19 l min-1 (p less than 0.01) with the WJB, RB and RSB, respectively. The mean oxygen consumption levels observed during the walks averaged 23% and 65% of the subjects maximum oxygen consumption on the treadmill and in the snow-field, respectively. During the walking tests the corresponding mean heart rates were 106 +/- 4, 93 +/- 5, and 95 +/- 5 beats min-1 (p less than 0.05) on the treadmill, and 151 +/- 11, 150 +/- 11 and 151 +/- 12 beats min-1 (NS) in snow. No significant differences in ratings of perceived exertion were observed between the walking tests in snow with the three types of boots. In accordance with earlier studies, walking in snow was found to be strenuous work. In conclusion, the use of the RSB is recommended during logging work in snow, since they are known to provide greater protection than lighter boots and the increase in physiological strain experienced with RSB in this study was not appreciably greater than that with boots of lighter weight.

Oxygen consumption and heart rate in different modes of manual postal delivery

Oxygen consumption ([Vdot]O2) and heart rate (HR) was measured in eleven healthy men (mean age 34·5 years) during five modes of simulated postal delivery: on level ground by foot, bicycle and push-cart, and on stairs by foot and push-cart. HR was measured telemetrically and samples of expired air were collected with a Kofranyi-Michaelis gas meter. Each delivery mode was performed twice; at the standard pace recommended by the postal authorities and at a free pace. [Vdot]O2 and relative aerobic strain (RAS) were in the same level in on-foot and cart delivery but HR was lower in cart than in on-foot delivery. In bicycle delivery [Vdot]O2, RAS and HR were on the same level as in stairs/on-foot and stairs/with cart delivery but significantly higher than in on-foot and cart delivery on level ground. For all delivery modes the free pace resulted in significantly higher physiological stress and strain than the standard pace. The mean values of the different delivery modes varied from 1·0 to 1·71/min for [Vdot]O2...

Energy expenditure and clearing snow: a comparison of shovel and snow pusher

In order to assess the energy demands of manual clearing of snow, nine men did snow clearing work for 15 min with a shovel and a snow pusher. The depth of the snowcover was 400-600 mm representing a very heavy snowfall. Heart rate (HR), oxygen consumption (VO2), pulmonary ventilation (VE), respiratory exchange ratio (R), and rating of perceived exertion (RPE) were determined during the work tasks. HR, VE, R, and RPE were not significantly different between the shovel and snow pusher. HR averaged (+/- SD) 141 +/- 20 b min-1 with the shovel, and 142 +/- 19 beats.min-1 with the snow pusher. VO2 was 2.1 +/- 0.41.min-1 (63 +/- 12%VO2 max) in shovelling and 2.6 +/- 0.51.min-1 (75 +/- 14%VO2max) in snow pushing (p < 0.001). In conclusion manual clearing of snow in conditions representing heavy snowfalls was found to be strenuous physical work, not suitable for persons with cardiac risk factors, but which may serve as a mode of physical training in healthy adults.

Effect of heat stress on muscle blood flow during dynamic handgrip exercise

SummaryDuring exercise in a hot environment, blood flow in the exercising muscles may be reduced in favour of the cutaneous circulation. The aim of our study was to examine whether an acute heat exposure (65–70°C) in sauna conditions reduces the blood flow in forearm muscles during handgrip exercise in comparison to tests at thermoneutrality (25° C). Nine healthy men performed dynamic handgrip exercise of the right hand by rhythmically squeezing a water-filled rubber tube at 13% (light), and at 34% (moderate) of maximal voluntary contraction. The left arm served as a control. The muscle blood flow was estimated as the difference in plethysmographic blood flow between the exercising and the control forearm. Skin blood flow was estimated by laser Doppler flowmetry in both forearms. Oesophageal temperature averaged 36.92 (SEM 0.08) ° C at thermo-neutrality, and 37.74 (SEM 0.07) ° C (P<0.01) at the end of the heat stress. The corresponding values for heart rate were 58 (SEM 2) and 99 (SEM 5) beats -min−1 (P<0.01), respectively. At 25° C, handgrip exercise increased blood flow in the exercising forearm above the control forarm by 6.0 (SEM 0.8) ml · 100 ml−1 · min−1 during light exercise, and by 17.9 (SEM 2.5) ml · 100 ml−1 · min−1 during moderate exercise. In the heat, the increases were significantly higher: 12.5 (SEM 2:2) ml · 100 ml−1 · min−1 at the light exercise level (P<0.01), and 32.2 (SEM 5.9) ml · 100 ml−1·min−1 (P<0.05) at the moderate exercise level. Skin blood flow was not significantly different in any of the test conditions between the two forearms. These results suggested that hyperthermia of the observed magnitude did not reduce blood flow in active muscles during light or moderate levels of dynamic handgrip exercise.

Towards sustainable well-being in SMEs through the web-based learning program of ergonomics

Promoting well-being at work in the context of sustainable development is a complex and dynamic issue. To enhance sustainable well-being at work, organizational learning (OL) is one requirement. The purpose of this study was to identify and describe the characteristics of the learning program of the ergonomics ‘the Ergonetti’ that promote sustainable well-being at work implemented in the small- and medium-sized enterprises (SMEs). The data was gathered through individual thematic interviews of 14 students who participated in the study and carried out the learning tasks in 10 different SMEs. The data was analyzed using inductive content analysis in the frame of sustainable well-being at work and organizational learning. The characteristics of the learning program of ergonomics that promoted sustainable well-being at work related to the categories describing worker’s individual capabilities and competence, work organization and environment, and leadership. The results suggest that, in the light of promoting sustainable well-being at work the learning program of ergonomics may be considered an efficient and straightforward distance learning program accessible through the Internet. In addition, sustainable well-being at work through learning is rarely being in focus of occupational health research.