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Aerobic work capacity
... Predicted maximal oxygen uptake (VO 2pMax :ml⅐kg Ϫ1 ⅐min Ϫ1 ) was calculated according to Wasserman's equations (17). HR peak was expressed in absolute value or as a percentage of the predicted maximum heart rate calculated according to the Astrand formula (HR pMax ϭ 220 Ϫ age [years] Ϯ 10) (16). Peak HR during the race was defined as the maximum HR recorded for any given subject during at least two consecutive minutes of any relay. ...
... This study indicates that the maximum heart rates recorded for endurance-trained HTRs during foot races are not significantly different from predicted maximum heart rates estimated according to the Astrand formula (16). Moreover the study demonstrates that the exercise tests performed on the treadmill yield more relevant information about the functional capacity of patients than do bicycle tests. ...
... Comparison between bicycle and treadmill exercise tests. (Table 5) Data published since 1964 (16,25,26) show that the VO 2max values of normal subjects running on a treadmill are about 10% higher than those resulting from exercise tests on a bicycle (25)(26)(27). The same findings were reported concerning patients with heart failure. ...
Objectives:
The purpose of this study was to show that the chronotropic potential of the well trained heart transplant recipient (HTR) does not limit exercise capacity.
Background:
Chronotropic incompetence is considered to be the main limiting factor of the functional capacity of heart transplant recipients. However, no systematic study had been published on patients who had spontaneously undergone heavy endurance training for several years.
Methods:
Heart rate (HR) and respiratory gas exchanges (VO2, VCO2, VE) were measured in 14 trained HTRs (T-HTRs) during exercise tests on a bicycle, on a treadmill and by Holter electrocardiography during a race.
Results:
Peak values observed in T-HTRs during the treadmill test were higher than those reached during the bicycle test (VO2peak: 39.8+/-6.9 vs. 32.5+/-7.8 ml x kg(-1) x min(-1), p < 0.001; HRpeak: 169+/-14 vs. 159+/-16 bpm, p < 0.01). During treadmill exercise VO2peak and HRpeak values observed were very close to the mean predicted VO2pmax and HRpmax. The maximum heart rate during the race (HRrace) was greater than HRpeak values during the treadmill test (179+/-14 vs 169+/-14 bpm, p < 0.01) and slightly above the mean predicted values (HRrace/HRpmax X 100 = 101+/-10%). The treadmill exercise test yields more reliable data than does the bicycle test.
Conclusions:
Extensive endurance training enables heart transplant recipients to reach physical fitness levels similar to those of normal sedentary subjects; heart rate does not limit their exercise capacity.
... Although it is widely accepted that an increased metabolic rate increases the steady-state core temperature during exercise (18), this relationship may not be true for comparisons between individuals. Astrand (5) first reported that the relative metabolic rate (% VO, max), rather than the absolute metabolic rate (VOr), removes most of the intersubject variability for the core temperature elevation during exercise (20). Our data clarify Astrand's principle: neither %YOrmaxnor VO2 are valid predictors of intersubject differences of T," in distance runners during strenuous exercise in the heat. ...
... Future research may lead to the development of a nontechnical field test that screens large numbers of athletes running on a track; we recommend that HR be evaluated as a predictor.3. Coaches and athletes must realize that (a) marked elevations in H& LA, and glucose foreshadow exhaustion(17), hyperthermia (72), or possible collapse(13); and (b) severe exercise-induced hyperthermia (T." > 39.5 'C) may result in heatstroke or death(12,L3). Once it is recognized that an athlete has low EHT, the coach should carefully monitor his or her progress during training and competition, and be prepared to seek emergency first aid and cooling if collapse or severe hyperthermia results(7).4. ...
... mL.kg -1 .min -1 ) is based on research that suggests for long duration activities, lasting up to eight hours, individuals should not work at more than 35 % of their maximal aerobic capacity (Astrand, 1960;Bink, 1962Bink, , 1964. ...
... Research suggests that for long duration activities, lasting up to eight hours, individuals should not work at more than 35 % of their maximal aerobic capacity (Astrand, 1960;Bink, 1962Bink, , 1964. A ̇O 2max of 46.3 mL.kg -1 .min ...
PURPOSE: To develop a Physical Employment Standard (PES) for the British Royal Air Force Regiment (RAF Regt). METHOD: Twenty-nine RAF Regt personnel completed eight critical tasks wearing Combat Equipment Fighting Order (31.5 kg) while being monitored for physical and perceptual effort. A PES was developed using task simulations, measured on 61 incumbents. RESULTS: The resultant PES consists of: 1) a battlefield test involving task simulations: single lift and point-of-entry (psss/fail); timed elements (react to effective enemy fire and crawl) set at 95th performance percentile; casualty evacuation (CASEVAC) casualty drag and CASEVAC simulated stretcher carry completed without stopping. 2) a Multi Stage Fitness Test level 9.10 to assess aerobic fitness to complete a tactical advance to battle. CONCLUSION: The task-based PES should ensure RAF Regt personnel have a baseline level of fitness to perform and withstand the physical demands of critical tasks to at least a minimum acceptable standard.
Practitioner Summary: A Physical Employment Standard (PES) was developed for the British RAF Regiment by measuring the physiological demands of critical tasks on a representative cohort of incumbent personnel. A task-based PES should ensure that only those candidates, irrespective of gender, race or disability, with the necessary physical attributes to succeed in training and beyond, are selected.
... mL.kg -1 .min -1 ) is based on research that suggests for long duration activities, lasting up to eight hours, individuals should not work at more than 35 % of their maximal aerobic capacity (Astrand, 1960;Bink, 1962Bink, , 1964. ...
... Research suggests that for long duration activities, lasting up to eight hours, individuals should not work at more than 35 % of their maximal aerobic capacity (Astrand, 1960;Bink, 1962Bink, , 1964. A ̇O 2max of 46.3 mL.kg -1 .min ...
... The %HRmax has for many years provided a practical substitute marker of the percentage of maximal aerobic power (%VO 2 max). This is based on the assumption that HRmax and VO 2 max coincide (Astrand and Rhyming, 1954;Astrand and Christensen, 1964). For an individual, heart rate for a given %VO 2 max does not change, regardless of training status, fitness level or age (Skinner, et al., 2003). ...
... Nevertheless, with age as the main predictor of maximal heart rate in all the above studies, this does not filter out the more individualised factors of autonomic regulation that influence heart rate from rest up to maximal exertion. Astrand and Christensen (1964) and Astrand, et al. (1973) cautioned that the error around the prediction of maximal heart rate based on age had a standard deviation of +/-10 beats · min -1 . This means that (Adapted from Pollock, et al., 1978;ACSM, 1994ACSM, , 1998ACSM, , 2000Noble and Robertson, 1996.) in some individuals their actual maximal heart rate could be as much as 20 beats · min -1 above or below the age-estimated maximum. ...
This article provides an overview of the process and application of cardiac rehabilitation following myocardial infarction and coronary artery bypass grafting. The authors discuss risk factor modification targeting smoking, serum cholesterol, hypertension, and exercise training. The role of the physician and the practitioner are addressed as well as the physiological and psychological benefits of cardiac rehabilitation.
... A quite peculiar, bizarre conclusion for a scientific paper, but a sincere testimony of the astonishment of the authors and of their inability to understand. ) as a function of age. Triangles: data on elite climbers (Oelz et al. 1986); dotted area: leisure marathon runners ); thick line: sedentary controls (Åstrand and Christensen 1964); thin line, professional alpine guides (Cerretelli, unpublished data); hatched area, elite marathon runners ). The red arrow indicates Messner's _ VO max 2 . ...
This chapter concerns the contribution of the School of Milano to the study of human responses to altitude exposure. Paolo Cerretelli’s contributions are firstly described. The studies performed during the expedition to Mount Kanjut-Sar, Karakorum, in 1957, and during the Italian Expedition to Mount Everest in 1973 are reported. This expedition generated a highly celebrated article, on the factors limiting oxygen transport on Mount Everest. The subsequent remarkable work on structural and functional muscle adaptation to altitude, performed along the Cerretelli–Hoppeler (Bern) axis is described. Then, Reinhold Messner attained the summit of Mount Everest without supplementary oxygen. Several projects devoted to understand Messner’s achievement (AMREE, by John West; the Messner’s study, set up by Oswald Oelz with Hoppeler and Cerretelli; Operation Everest II) are analyzed. Finally, Cerretelli’s work at the new Italian laboratory close to the Everest basecamp (the Pyramid) is reported. Secondly, the studies coordinated by Giuseppe Miserocchi concerning the complex interaction between lung diffusion, alveolar-capillary blood volume, and lung water balance to affect the kinetics of alveolar-capillary equilibration on increasing oxygen demand is developed. Further, inter-individual differences in the proneness to develop pulmonary edema at altitude are related to specific morpho-functional features of the alveolar-capillary network.
... A quite peculiar, bizarre conclusion for a scientific paper, but a sincere testimony of their astonishment and inability to understand. ; dotted area: leisure marathon runners ; thick line: sedentary controls (Åstrand and Christensen, 1964); thin Line, professional alpine guides (Cerretelli, unpublished data); hatched area, elite marathon runners . The red arrow indicates Messner's ̇2max . ...
This chapter presents an integrated view of the various functions of the air–blood barrier considered as an interface for gas exchange. “Safety factors” are being described allowing to exert a strict control on the amount of the extravascular water that is kept at minimum in physiological conditions to favor oxygen uptake. The key role of the macromolecular structure network of the lung interstitial tissue is described to guarantee a minimal microvascular permeability; further, the role of precapillary vasoconstriction is emphasized to avoid an increase in alveolar-capillary pressure. The physiopathology of lung edema is described as a progressive failure of the “safety factors” in edemagenic conditions such as exercise and exposure to hypoxia. The kinetics of the oxygen diffusion/transport mechanism is discussed as a function of age (fetal, neonatal, adult), oxygen demand (rest, exercise), and development of lung edema. The inter-individual differences in the kinetics of oxygen uptake are being correlated with morpho-functional features of the air–blood barrier based on diffusion capacitance and extension of the capillary network. The chapter also reports data on the reflex response to pollutants, and results from an applied developmental project for drug uptake across the air–blood barrier via engineered nanoparticles.
... For some of these tests, however, lack of reference values and the absence of physiological measures are important limitations. In healthy subjects, a fairly good cor- [17][18][19]. ...
Key points
An exercise test should be performed: if there is impaired exercise tolerance; to find out which system is limiting exercise; to establish which organ systems have an abnormal response during or after exercise; to investigate how much exercise is appropriate/safe in a patient; and to determine the response to treatment.
Prediction of exercise performance based solely on resting pulmonary function tests is inaccurate.
The gold standard in exercise testing is the incremental exercise test.
Two types of ergometers can be selected for incremental exercise testing: a treadmill or a cycle ergometer. More muscle mass is put to work using a treadmill when compared with cycling.
Incremental exercise testing and field testing have complementary value in, for example, pulmonary rehabilitation.
Exercise laboratories should be encouraged to test some healthy control subjects in the age span of interest to evaluate which normal values best suit their laboratory setting.
Educational aims
To address some questions that often arise when exercise testing is performed in the clinical routine: What are the indications to perform an exercise test?
Which test should be used for which situation?
How should the test be carried out in practice?
How should the results of the test be interpreted?
Summary
Exercise testing is widely applied in clinical practice. The aim of this article is to address some questions that often arise when exercise testing is performed in clinical routine. Two complementary tests will be discussed in more detail: the maximal incremental ergometer test and the timed walk test.
First, the indication to perform exercise testing is discussed. The second question is which test to apply and how to carry out the test in practice. Finally, the interpretation of the results of the tests are discussed.
... The bench stepping tests were developed with single stage and multistage protocols. Several researchers examined the efficiency of stepping and found it related to physical characteristics of the participants such as stature (Ashley, Smith & Reneau, 1997), age (Astrand, 1960), leg length (Culpepper & Francis 1987), and body weight (Marriott & Gumstrup-Scott 1992). Numerous studies also investigated the effect of other factors including the methods of heart rate measurement, tempo and step height on the stepping test performance (Francis & Brasher, 1992;Francis & Culpepper, 1988;Golding 2000;McArdle, Katch & Katch, 1991). ...
This study compared the performance of university females in Hong Kong with different ages and physical activity participation levels on two 3-minute step-tests using different cadences. Fifty-six students were classified into three groups. They performed two step-tests randomly on a 30-cm high bench with a metronome (MN) and hip-hop music (HH) cadences at 96 beats ·min-1 with 60 min rest between. The preference for either cadence was indicated upon completion of both. The rate of perceived exertion was reported at 2-min (RPE2) and 2.5-min (RPE2.5). Heart rates at rest (by monitors, HRr) and 1-min post-exercise (by monitors, HRh; by pulse, HRp) were recorded. Results indicated that more than 80% of them preferred HH. Among all groups, although paired t-tests showed no significant differences (p>0.05) between the performance of MN and HH, the latter elicited a higher HRp, HRh, RPE2 and RPE2.5, and both cadences were highly correlated (r=0.70-0.91, p<0.001). MANOVA showed no significant differences for the responses of HRp, HRh, RPE2 and RPE2.5 under the two-stepping cadences (Hotelling's Trace=0.27, p>0.05). There was no interaction between age and physical activity participation level (Hotelling's Trace=0.23, p>0.05). HH seemed a reliable cadence for a 3-min step-test in females of different ages and physical activity participation levels.
... The bench stepping tests were developed with single stage and multistage protocols. Several researchers examined the efficiency of stepping and found it related to physical characteristics of the participants such as stature (Ashley, Smith & Reneau, 1997), age (Astrand, 1960), leg length (Culpepper & Francis 1987), and body weight (Marriott & Gumstrup-Scott 1992). Numerous studies also investigated the effect of other factors including the methods of heart rate measurement, tempo and step height on the stepping test performance (Francis & Brasher, 1992;Francis & Culpepper, 1988;Golding 2000;McArdle, Katch & Katch, 1991). ...
LANGUAGE NOTE | Document text in English; abstract also in Chinese. This study compared the performance of university females in Hong Kong with different ages and physical activity participation levels on two 3-min step-tests using different cadences. Fifty-six students were classified into three groups. They performed two step-tests randomly on a 30-cm high bench with metronome (MN) and hip-hop music (HH) cadences at 96 beat·min-1 with 60 min rest between. The preference of either cadence was indicated upon completion of both. Rate of perceived exertion was reported at 2-min (RPE2) and 2.5-min (RPE2.5). Heart rates at rest (by monitors, HRr) and 1-min post-exercise (by monitors, HRh; by pulse, HRp) were recorded. Results indicated that more than 80% of them preferred HH. Among all groups, although paired t-tests showed no significant differences (p>0.05) between the performance of MN and HH, the latter elicited a higher HRp, HRh, RPE2 and RPE2.5, and both cadences were highly correlated (r=0.70-0.91, p<0.001). MANOVA showed no significant differences for the responses of HRp, HRh, RPE2 and RPE2.5 under the two stepping cadences (Hotelling’s Trace=0.27, p>0.05). There was no interaction between age and physical activity participation level (Hotelling’s Trace=0.23, p>0.05). HH seemed a reliable cadence for 3-min step-test in females of different ages and physical activity participation levels. 本研究探討採用音樂與節拍器拍子於三分鐘登臺階測試對不同年齡和運動習慣的女生之影響。五十六名女生根據她們的年齡和參與運動習慣分成三組。她們以隨機排序採用節奏強烈的音樂和傳统節拍器拍子完成兩次三分鐘登階測試。每次測試相距不少於六十分鐘。結果顯示超過八成女生較喜用音樂拍子，她們在两種拍子的身體反應並無差異(P>0.05)，年齡和參與運動習慣並無互動效果。結果證實在三分鐘登臺階測試中音樂拍子可以有效地取代單調節拍器拍子。
... This test was conducted on the treadmill and the experiment was conducted at natural environmental condition (28.3 + 2.1 o C and 73 + 8.4 R.H) in the Human Engineering Laboratory at Agricultural Engineering College & Research Institute, TNAU, Coimbatore. The maximum heart rate attainable by the each subjects was computed by the following relationship (Astrand, 1960 andMaritz et al., 1961). ...
... The corresponding heart rate was recorded using Polar Vantage NV computerized heart rate monitor (S 810i) at the submaximal loads. The maximum heart rate of all the selected individuals was computed using the equation proposed by Astrand (1960) and the arrived values of maximum aerobic capacity (VO 2 maximum) for all the individuals. Because of the advantages of the indirect assessment of oxygen uptake, during the operation of each of the selected knives, only the heart rate of the subject performing the task was noted. ...
Ergonomic evaluation of farm tools is necessary to improve the fit between the physical demands of the tools and the worker who perform the work. In spite of improved farm mechnization, the use of the hand tools is inevitable in certain agricultural operations like sugarcane harvesting. Commonly used and high energy demanding tools like sugarcane harvesting knives of various models available in India were selected to assess the ergonomic suitablity. Ten individuals were selected for the investigation based on the age and fitness. They were screened for normal health through medical investigations. Four models of sugarcane harvesting knives were selected for ergonomical evlauation. The parameters used for the ergonomical evaluation of screened sugarcane harvesting knives include heart rate and oxygen consumption rate, energy cost of operation, acceptable work load, over all discomfort rate and body part discomfort score. The maximum aerobic capacity of the selected ten individuals varied from 1.84 to 2.19 L min-1 for sugarcane harvesting. The heart rate and oxygen consumption rate of the sugarcane knives varied from 132.55 to 138 beats min-1 and 1.171 to 1.253 L min-1 , respectively. The energy cost of sugarcane harvesting knives, varied from 24.45 to 26.16 kJ min-1 respectively. The values of percent maximum aerobic capacity (VO 2 maximum) and work pulse for sugarcane harvesting knives were much higher than that of the acceptable workload (AWL), limits of 35%. Based on the analysis of results, the sugar cane harvesting knife (H1) ranked as I in terms of minimum value of heat rate (132.55 beats min-1), energy cost of work (24.45 KJ min-1), acceptable work load (58.14%), over all discomfort rate (moderate discomfort) and Body part discomfort score (29.39) when compared with other three models (H2, H3 and H4) of sugarcane harvesting knives.
... While regional heat losses have been demonstrated in male surfers, data suggest that males and females may respond differently to cold stress. Specifically, in response to cold stress, females generally exhibit a decrease in maximum heat production generated by either shivering or exercise [18], lower mean skin temperatures resulting in increased body heat debt [19,20], and accelerated rate of extremity cooling [21]. Potential mechanisms for these responses include lower total body mass, greater relative body fat percent [22], differences in body fat distribution [23], lower skeletal muscle mass [23,24], and decreased arterial flow to the hands and feet [21] compared to males. ...
The aim of this investigation was to examine regional skin temperatures in recreational female surfers’ wearing a 2 mm thick neoprene wetsuit while surfing and to compare these results to previously published data collected in males participating in an identical study. Female surfers (n = 27) engaged in surfing for at least 40 min while wearing a commercially available 2 mm full wetsuit. Skin temperature of eight different anatomical locations were measured with wireless iButton thermal sensors. Regional skin temperatures significantly differed (p < 0.001) across almost all anatomical regions. Furthermore, regional skin temperatures significantly decreased across time at all skin regions throughout an average surfing session (p < 0.001). The greatest reduction in skin temperature was observed in the lower leg (−5.4 °C). Females in the current study exhibited a significantly greater skin temperature decrease in the lower back (−15.2% vs. −10.8%, p = 0.022) and lower arm (−13.6% vs. −10.8%, p < 0.001) when compared to previous data published in males. Overall, results of the current study are consistent with data previously published on male recreational surfers. However, the current study provides preliminary evidence that the magnitude of change in skin temperature may differ between male and female recreational surfers at some anatomical locations.
... bpm). A workload of 33% of the aerobic capacity is recommended as the maximum energy expenditure for an eight hour work day [1,10]. Its corresponding heart rate is 105 bpm with a range of 95 to 115 bpm [9]. ...
This study concerns with the repetitive asymmetric lifting task of centrifugal-pump
casings (CPC) in a medium scale factory in Agra. CPC are lifted to drilling machine from six
heights, as six CPC are stacked in a column. Task variables of revised NIOSH lifting equation
are noted down from the factory site to compute lifting index for all six heights. HM and
AM are found to be less or more constant, however VM, DM and FM vary with respect to
vertical travel distance. Lifting turns out to be physically stressful for all six heights. In fact,
it becomes increasingly stressful with respect to increase in vertical travel distance. Task is
redesigned to make it safer by reducing asymmetry to an extent. To assess risks involved in
the lifting task physiologically, factory site lifting is simulated in the Industrial Kinesiology
Lab (DEI). Experiments are conducted on 10 male workers. Heart rate is recorded before and
after each experiment. A mismatch between the results of revised NIOSH lifting equation
and physiological results is observed. Heart rate of subjects after the experiments is found
to fall in the safer range. Re-sults raise questions on the applicability of revised NIOSH lifting
equation.
... individual subjects [38][39][40]. Nonetheless, incremental exercise testing and field testing have complementary value in assessment for pulmonary rehabilitation [41]. ...
... The corresponding heart rate was recorded using Polar Vantage NV computerized heart rate monitor (S 810i) at sub maximal loads. The maximum heart rate of all the selected male and female subjects was computed using the equation proposed by Astrand (1960) and the arrived values of maximum aerobic capacity (VO 2 maximum) for all the subjects. The maximum aerobic capacity of the selected twelve male subjects varied from 1.84 to 2.19 l min -1 and, for female subjects, from 1.513 to 1.736 l min -1 . ...
Sugarcane detrashing is a highly labour intensive operation. Conventional detrashing by hand leads to serious health hazards for the workers. In view of the importance of the detrashing operation, mechanical detrashers have been introduced. The available mechanical detrashers viz., IISR sugarcane detrasher, OUAT sugarcane detrasher and TNAU sugarcane detrasher with selected male and female subjects were ergonomically evaluated to assess their suitability for men and women farm workers for reduced drudgery and adequate comfort. The detrashing was performed between 150 to 210 days after planting. The TNAU sugarcane detrasher (SCD3), which registered the lowest value of ergonomic evaluational parameters and highest stripping capacity with minimum damage to sugarcane stalks was identified. Necessary ergonomie refinements (viz., reduction of length of knife supporting stem, sliding supporting stem and knife base, wooden handle for firm grip and reduction of weight) were made for enhanced comfort of the operator without jeopardizing the efficiency of the detrasher. The mean value of heart rate, energy cost, and oxygen consumption rate in terms of percent VO2 maximum and work pulse of male subjects with the refined TNAU sugarcane detrasher (ESCD) was 101.12 beats min -1, 14.74 kJ min-1, 34.88 percent of VO2 maximum and 30.55 beats min-1, respectively. The corresponding values for female subjects were 112.76 beats min-1, 16.52 kJ min -1, 47.91 percent of VO2 maximum and 44.35 beats min -1, respectively. The effectiveness of ergonomie refinements made with the sugarcane detrasher was reflected in terms of significant reduction in physiological stress and 4.9 percent increase in stripping capacity. The ergonomie refined TNAU sugarcane detrasher resulted in 5.5-6.6 percent savings in cost and 5.6-5.8 percent savings in time of detrashing when compared to the existing model of the TNAU detrasher. Use of the ergonomie refined TNAU detrasher resulted in 13.0 percent and 14.5 percent saving in cost and time, respectively, when compared to conventional hand detrashing.
... This test was conducted on the treadmill and the experiment was conducted at natural environmental condition (28.3 + 2.1 o C and 73 + 8.4 R.H) in the Human Engineering Laboratory at Agricultural Engineering College & Research Institute, TNAU, Coimbatore. The maximum heart rate attainable by the each subject was computed by the following relationship (Astrand, 1960 and Maritz et al., 1961). Maximum heart rate = 190 -(Age in years – 25) x 0.62 ----- (1) ...
A simple motorized device was designed and constructed for okra slicing using locally available
materials. The slicing mechanism was based on the high shear stress that is generated when a knife edge
is brought into contact with a non-fibrous bio-material causing the knife to move in a direction parallel to
its edge and perpendicular to the direction of the applied force. The device was evaluated based on slicing
efficiency and throughput time of the okra fruits. The machine was tested with replicated experimental
runs using 400g, 500g, 1000g and 1150g of Okra. The machine gave the best slicing efficiency of 85.7%
and throughput of 21 kg/hr.
... The quantification of aerobic contribution to maximal exercise performance is difficult because the mechanical efficiency (ME) during a non-steady state exercise task remains speculative [3]. Nevertheless extreme ME values for cycling [11] have been proposed to provide a general scope of the estimated values [20]. ...
The aerobic energy contribution to a 30-s Wingate Anaerobic Test (WAnT 30 s) was examined in 18 boys and 18 girls aged 10-12 years. Participants completed an incremental test to volitional exhaustion to determine peak oxygen uptake (VO 2) and a WAnT 30 s on two separate occasions on a cycle ergometer (Monark 834E). VO 2 during the tests was monitored breath-by-breath using an on-line gas analysis system (SensorMedics). WAnT 30 s VO 2 amounted to 67% and 73% of peak VO 2 in boys and girls, respectively. By assuming extreme mechanical efficiency (ME) values of 15% and 35%, the aerobic contributions to the WAnT 30 s in boys and girls were between 16% and 45%. Peak VO 2 and WAnT 30 s power were higher in boys than in girls but there was no sex difference in the aerobic energy contribution to the WAnT 30 s for the same assumed ME. The magnitude of the aerobic energy contribution to the WAnT 30 s reflected plausibly a swift oxygen uptake response to maximal intensity exercise and perhaps a reduced reliance on non-oxidative metabolism in boys and girls.
... HR is also used for exercise prescription, as it is a marker of physiological strain on the skeletal muscles and with systolic blood pressure can be used as a marker of myocardial strain (Thow, 2006). The ease of being able to monitor HR and its direct relationship with VO 2 max is why HR has become the most commonly measured exercise response (Buckley, Holmes & Mapp, 1999) & (Astrand & Christensen, 1964). This relationship between HR and VO 2 max allows for the same exercise prescription to be applied to all persons regardless of age or physical state. ...
... The relationship between metabolic rate and core temperature is good for a given individual, but does not always hold well for comparisons between different individuals. Astrand (6) first reported that the use of relative intensity (percent of maximal oxygen uptake), rather than actual metabolic rate (absolute intensity), 35 removes most of the inter-subject variability for the core temperature elevation during exercise. Figure 3-7 shows the relationship of steady-state core temperature to both absolute and relative intensities in a moderate environment (130). ...
The sections in this article are:
Until about two and half centuries ago, muscle power was the prime source of energy for performing all the physical activities on our earth, and much of this power had been from human muscles. Because of the socio-economic conditions of farmers in developing countries including India, human muscle power is going to contribute energy requirements for performing many farm activities for the next two decades. Pedalling is the most efficient way of utilising power from human muscles. Pedal power enables a person to drive devices at the same or higher rate as that achieved by hand cranking, but with far less effort and fatigue. However, the use of pedal power for occupational work such as stationary farm operations has got scant attention in the past. Keeping these points into consideration a study was planned for Effect of workload and pedalling rate on physiological response for male worker. Physiological responses of 20 male subjects were studied on a computerised bicycle ergometer at four levels of power output (60, 70, 80, 90 W) four levels of pedalling rates (40, 50, 60, 70 rev/min). Analysis of data indicated that physiological responses were significantly affected with power output as well as pedalling rate. Increases in physiological responses (heart rate and oxygen consumption rate) over rest were significantly higher when pedalling frequency was 50rev/min and above 60rev/min. There was no significant difference between physiological responses at 50 and 60 rev/min. Physiological responses increased linearly with power output and were significantly different at different power outputs. The average value of physiological responses at 60W power output at male agriculture worker at 50rev/min pedalling rate were within acceptable limits for continuous pedalling work.
It is the responsibility and goal of those working in the field of ergonomics to ensure that job demands do not exceed the abilities of employees and to keep a job at a level that can be done all day long. The employee, who is expected to work constantly above the performance limit, gets tired. Fatigue can create negative effects in terms of work efficiency, health, safety and psychological balance of employees. Metabolic energy expenditure rate is a physiological measurement used to determine the maximum work intensity that can be performed continuously without accumulating excessive physical fatigue. In this study, the evaluation of metabolic rate and energy load in the logistics department of a rubber hose manufacturing enterprise was achieved using the metabolic rate expenditure model for manual material handling works. In the current situation, the metabolic energy expenditure rate of the employee was found to be 6,564 kcal/min. With the new conveyor system developed, the metabolic energy expenditure rate was reduced to 4.872 kcal/min and it was kept below the limit value.
Literature concerning variables affecting performance levels of males and females was reviewed. Emphasis was placed on literature using both males and females as subjects in the areas of anthropometric, biomechanical, and physiological variables. When literature using both sexes as subjects was not available, comparable studies were considered for possible use.
The results of this review indicate that there are sex differences in anthropometry with regard to body dimensions. In biomechanics, sex differences were noted in reach envelopes strength and flexibility in particular. Physiological differences were noted in responses to heat/cold stress and altitude. These differences were then applied to a performance matrix under the categories of sensory, process and control. Differences noted were either very specific or did not exist at all. This is due in part to a lack of research involving variables as they actually affect performance levels between males and females.
Background
Modern lifestyle is heavily affected by technology such as smartphones, tablets, and other small computers; yet it remains unclear how our health and well-being are affected by the heavy use of these devices.
Objective
This feasibility study aims to test two different interventions of an experimental protocol for a forthcoming large-scale community-based study and get estimates of parameters for sample size calculation. The aim of the large-scale study is to investigate the effect of (1) a wearable tracking device on aerobic capacity (VO2max/kg) and the effect of (2) restricting media use on total sleep time.
Methods
Twenty healthy participants were included and equipped with a wrist-worn device tracking physical activity and sleep. Participants were allocated to either a physical activity group, which was instructed to use the wrist-worn device to support exercise, or a sleep silent group, which was instructed to remove or switch off all electronic devices in the bedroom (except the wrist-worn tracking device). The intervention lasted approximately 4 weeks. Data collected included blood pressure, submaximal cycle ergometer test, self-reported technology use, and compliance of using the wearable tracking device.
Results
All participants wore the wearable tracking device 95.8% (SD 4.4%) of the time. Participants in the physical activity group increased aerobic capacity from 30.38 (SD 8.98) to 32.1 (SD 8.71) mL/kg/min (t=–2.31, P=.046) and decreased their systolic blood pressure from 126.5 (SD 15.8) mm Hg to 121.8 (SD 11.7) mm Hg (t=2.72, P=.02). The sleep silent group prolonged their time offline before bedtime from 18.1 (SD 19.4) minutes to 27.2 (SD 17.3) minutes (t=–2.94, P=.02).
Conclusions
The two interventions are feasible to conduct. Participants were willing to wear the tracking device on their wrist and restrict all media use in their bedroom and thereby reduce bedtime technology use. Our results also suggest that tracking physical activity using a wearable device is accompanied by noteworthy health benefits. We outline necessary adjustments for a forthcoming large-scale study.
This chapter presents a comparison of women and men with regard to their response to strength and endurance training, sports related injuries, performance in hot and cold environments, and the effects of exercise on bone-mineral metabolism, blood chemistry, and reproductive physiology. Medical science recognizes that physical exercise and conditioning are important for the physical and mental health of both women and men. It is reasonable to conclude that women are not more susceptible to injury than men. Although relatively less-fit men and women are likely to be injured than better-fit individuals, there are no anatomical or physiological reasons for excluding women from any sports endeavor, provided she is sufficiently conditioned to participate. The exercising male, with relatively greater working muscle mass, produces more heat than a woman performing at the same relative workload, but the male has proportionally less body surface area over which heat loss occurs. Thus, the female has the advantage of less heat production and relatively greater surface area over which heat is dissipated. Numerous anecdotes of women who exercise throughout their pregnancy reveal that the health benefits of exercise continue throughout their pregnancy. The modern woman feels free to participate in sports and athletics uninhibited by social taboos. She does not fear losing her femininity by participation in physical conditioning and sports.
Tantalizing research in nutrition in the past few years has promised the possibility of extending life span, delaying the effects of aging, preventing chronic disease, and augmenting the body’s immune function. Yet, the current state of the art seems to raise more questions than solutions.
Hand weeding requires more labour, consumes more time and leads to higher cost. Hence, inter cultivation of weeds using mechanical power was a viable and economical solution for this problem. The TNAU-Varun power weeder, Balram power weeder and Oleo power weeder with 12 male subjects were ergonomically evaluated. The weeding in cotton with the power weeders was performed on 30 and 60 DAS at 1.5, 1.8 and 2.1 km h"1 forward speed of operation. Heart rate, energy cost, oxygen consumption rate in terms of VO2 maximum and work pulse with the TNAUVarun power weeder was 123.32 beats min-1, 23.00 kJ min1, 52.34 % of VO2 maximum and 46.47 beats min 1, respectively. The corresponding values for the Oleo power weeder was 130.19 beats min1, 23.96 kJ min1,57.40 % of VO 2 maximum and 47.82 beats min1, respectively. For the Balram power weeder, the values were 134.09 beats min1, 24.45 kJ min1, 58.59 % of VO2 maximum and 44.42 beats min 1, respectively. With the increase in forward speed, the mean heart rate and the corresponding oxygen consumption rate increased for all the weeders. The energy cost of the weeding operation was graded as "Heavy" at all levels of forward speed of the three power weeders. The energy cost of weeding was the maximum for the Balram power weeder and minimum for the TNAU Varun power weeder. In general, forty five minutes of work followed by 8-12 minutes of rest was required by the subjects for the power weeder operation. The Oleo power weeder had the highest weeding efficiency of 73.4 %. The savings in cost with TNAU-Varun, Oleo and Balram power weeders was 21.5, 16.2 and 23.1 %, respectively, when compared with manual weeding. The savings in time was 59.8, 58.6 and 59.8 %, respectively, when compared with manual weeding.
Cultural practices and their mechanization level in the production of major cereal and horticultural crops in the Kashmir Valley are presented. Except for ploughing and puddling, all farm operations were done manually using traditional tools and implements. A number of suitable improved tools and implements were identified to bridge the existing mechanization gap for major cereal and horticultural crops of the region. Some of the operations needed immediate attention of researchers for development of new tools/implements or introduction of previously developed implements in the region after feasibility testing. Apart from this, a State Policy for farm mechanization should be made to encourage mechanization on a sound footing.
Cardiovasculaire training is een be-langrijk middel in sportcentra en bij be-handeling in de (sport) fysiotherapeuti-sche praktijk. De laatste jaren is veel geschreven over rekenformules die een voorspelling geven van de maximale hartfrequentie. De eenvoudigste en meest gebruikte rekenformule is: 220 – leeftijd (1). Maar hoe nauwkeurig is deze berekening/schatting en welke formule is (wanneer) het beste? De maximale hartfrequentie is de hoogst mogelijke hartfrequentie bij een lichamelijke (sport)activiteit. Een for-mule voor het berekenen van Hfmax wordt gebruikt als je de Hfmax van een persoon niet weet en deze niet wilt of kunt meten maar moet schatten. Voor het berekenen, dus het schatten, van iemands maximale hartfrequentie zijn er vele formules in omloop. Voor dit artikel zijn, met behulp van geauto-matiseerde literatuurbestanden en zoekmachines, 12 verschillende reken-formules getraceerd en uitgekozen. Zonder te pretenderen dat deze lijst compleet is, geeft dit dus wel aan dat er vele verschillende formules bestaan 6 S p o r t g e r i c h t n r. 2 / 2 0 0 7 – j a a r g a n g 6 1 FYSIOLOGIE De intensiteit van cardiovasculaire training wordt vaak bepaald aan de hand van een percentage van de maximale hartfrequentie (Hfmax) of een afgeleide daarvan. In de trainingsliteratuur (en op Internet) zijn veel verschillende formules te vinden om de maximale hartfrequentie te bere-kenen. In dit artikel worden verschillende methoden voor het berekenen van de maximale hartfrequentie vergeleken en toegelicht, en worden de consequenties voor de praktijk weergegeven.
Several microprocessor exercise physiology systems have been introduced recently. Comparison of the data output between these systems and more traditional nonautomated systems has not been reported extensively. Twelve normal adult men were exercised in random sequence on different days on a Sensormedics MMC Horizon system, the Medical Graphics Corporation System 2000, and a nonautomated system. heart rate, minute ventilation, tidal volume, respiratory frequency, oxygen consumption, and carbon dioxide production were compared at each level of work during a maximal incremental test and during a constant work load test. The overall data output between the three systems was comparable. However, minute ventilation was consistently higher on the Medical Graphics system, oxygen consumption was consistently lower on the Horizon system, and a technical error was discovered in the Medical Graphics system which resulted in a systematic overestimation of carbon dioxide production. Different methods of analyzing the data from the same test (60-s average, 15-s average, breath-by-breath, and 8-breath average) resulted in differences of up to 20 percent in the maximal values. This was greater than the differences between the three systems. Despite the comparability of the data output, important differences did exist which can be potentially significant when data output from one system are compared to predicted normal values obtained under different conditions.
Eighteen cardiorespiratory parameters are measured in a five-minute bicycle ergometer test applied before and after four hours of resting (control days) or four hours of treadmill walking at 40, 50, and 60% of the maximum aerobic capacity (exercise days) of four volunteer subjects. There is no significant difference between control and exercise days in 16 out of 18 responses when the mean differences between the results obtained in the ″before″ and ″after″ tests are compared. The two exceptions are resting and exercise heart rate at 50 and 60% of the maximum aerobic capacity. Consequently, nine parameters showing the largest changes on exercise days are selected for calculation of a cardiorespiratory variance score (CVS). Subjective feeling of fatigue quantitated by the feeling tone checklist of Pearson are significantly correlated with CVS. There is also a significant relationship between work strain and the CVS. Within equal CVS values, deviation of single parameters may vary day by day in the same individual at identical work loads indicative of instability of homeostatic control during fatigue.
A study was undertaken to compare the cardiac and ventilatory responses to different types of exercise between 12 patients with COPD and ten normal age-matched control subjects. Both groups attained comparable heart rates and the percentage of their maximum predicted heart rate. Patients had a higher heart rate and VE with a lower O2P at every level of work load. Patients had a mean VT which approximated their FEV1 and increased their VE predominantly by increasing their respiratory frequency. During the low intensity test, despite the differences in work load, the patients had comparable heart rates and VE. No resting spirometric value accurately predicted work load, VE, or maximal VO2. We conclude that patients have a reduced work tolerance that is not adequately explained by their reduced lung function. Thus, cardiac factors, deconditioning, and the dyspneic sensation may be determinants of exercise limitation in some patients.
This paper gives the information regarding cultural practices and their mechanization level in the production of major cereal and horticultural crops in the Kashmir Valley. It was found that except ploughing and puddling, all the farm operations were done manually using traditional tools and implements. A number of suitable improved tools and implements were identified to bridge the existing mechanization gap for major cereal and horticultural crops of the region. Some of the operations need immediate attention of researchers for development of new tools/ implement or introduction of elsewhere developed implements in the region after their feasibility testing. Apart from this, A State Policy for farm mechanization should be made to encourage mechanization on sound footing.
Fifteen previously sedentary men (38–55 years old) participated in an endurance training program which consisted of running for 2–3 half-hours a week for 8–10 weeks. Maximal oxygen uptake increased in all subjects, mean increase from 2.68 to 3.06 l/min, i.e. 14 per cent. This increase was brought about by a 13 per cent increase in maximal cardiac output, from 18.7 to 21.1 l/min. Heart rate was 8–17 beats/min lower during submaximal exercise. The maximal heart rate decreased by 6 (from 182 to 176) beats/min. Thus stroke volume was increased 7–17 ml at submaximal and 17 ml (16 per cent) at maximal exercise. Heart volume determined from X-rays did not change. After the training, mean arterial blood pressure was on the average 5 mm Hg lower at a given submaximal oxygen uptake; no change was observed at maximal exercise.
Historically women have demonstrated the capacity to be successful aviators. Recent participation of women in combat roles and in military aviation has, however, aroused controversy. The scientific literature pertinent to the role of women in military aviation was reviewed. Cognitive differences between men and women account for less than 5% of the population variance and their implication for aviation is unknown. The effect of cyclic hormone fluctuations on performance is poorly understood. Men are, on the average, larger, stronger, and more fit than women, although there are large variations within each sex and a large overlap between the sexes. Difference in work performance, injury rate, etc., disappear when size, strength and fitness are controlled for. Selection criteria can thus address size, strength, and fitness requirements without reference to sex. Several minor differences of questionable operational significance may exist. Women may be more susceptible to motion sickness, heat stress, radiation (cancer and endometriosis), and decompression sickness than men, but may be more resistant to cold stress and altitude sickness. The possibility of fetal damage in the early stages of pregnancy (before diagnosis of pregnancy) appears to be perhaps the biggest single medical concern in allowing women access to all aviation/space careers.
This report provides a comprehensive overview of the normal human physiological responses to environmental and exercise-related heat stress, with emphasis placed on acute heat exposure and acclimation produced by repeated heat exposure. In addition, the report reviews biomedical factors that modify exercise-heat tolerance such as aerobic fitness, dehydration, circadian patterns and sleep loss and medications. Also, the report reviews thermoregulatory responses of special populations such as women, blacks, children, older adults and spinal cord injured populations. Temperature Regulation, Body temperature, Heat stress, Heat loss, Sweating, Skin blood flow
1.1. The procedure used to compare the forced running performance of three rodent species was the number of electrical stimuli required each minute to keep the animals running.2.2. During running trials, ground squirrels, Spermophilus tridecemlineatus, required fewer stimuli than white rats. Squirrels ran 12.4 ± 6.9 (2 SE) min before requiring stimulation vs 3.1 ± 1.4 min for rats.3.3. Total oxygen consumption during the running period was significantly higher for ground squirrels than white rats, 4.70 ± 0.36 and 4.18 ± 0.38ml O2/g/hr, respectively.4.4. Heart weight/body weight ratios were significantly higher for the ground squirrels than the white rats.5.5. No differences were noted between ground squirrels and chipmunks other than those which could be accounted for by body weight differences.
Data are presented on the physiques, physical fitness, serum lipids, blood pressures and smoking habits of 1,500 men and 700 women, and on the physical activity and dietary habits of small sub-samples. The subjects were residents of Adelaide (pop. 900,000) volunteering for fitness courses, and were mainly from middle and upper-middle income groups. Fifty per cent of the men and 37% of women were more than 10% above ideal body-weight, 36% and 28% respectively had elevated serum cholesterol (≥ 6.4 mmol/1), 29% and 9% had elevated triglycerides (≥ 2.0 mmol/1), and 21% and 17% had elevated diastolic blood pressures (≥ 95 mmHg). By overseas standards physical fitness was quite low in the men, and moderate in the women. Cigarette smoking was 10% less prevalent in both sexes than in the general Australian population. Average total daily energy intake was 10,290 kilojoules (2,450 cals.) for men, and 7,375 kilojoules (1,756 cals.) for women, with 11.4% of energy provided by alcohol in male drinkers, and 4.5% in female drinkers. Diet was relatively rich in “empty kilojoules” and cholesterol. Both sexes took little vigorous exercise but the women were less sedentary than the men. It is suggested that the biological profile of this sample is unsatisfactory, probably reflects the status of the urban population in general, and indicates the need for systematic health promotion. The value of the kind of information presented here, in relation to health programmes, is discussed.
To test a prediction of bodily restorative and energy conservation theories of sleep, the effect of physical exercise and aerobic fitness on the level of slow wave sleep and sleep duration were assessed in younger (average age 22 years) and older (average age 41 years) subjects. The design of the experiment consisted of two levels of fitness (fit and unfit), two age groups and two levels of exercise (exercise and no exercise). However, the design was not a complete factorial as the unfit subjects did not exercise. Two consecutive nights were run in each condition and an extended sleep paradigm was used to assess fully sleep duration. The level of exercise and the fitness of the subjects were selected to maximize the hypothesized effects. The results indicated that exercise did not increase either slow wave sleep or sleep duration; if anything, it disrupted sleep, particularly on the second of the two consecutive exercise nights. Aerobic fitness was associated with increased slow wave sleep and decreased sleep onset latency in both age groups. The data was interpreted as being incompatible with predictions derived from restorative and energy conservation theories.
The noradrenaline (NA) levels in arterial blood plasma were followed at rest and during increasing muscular exercise in 5 healthy men. The levels were found to be significantly correlated to the oxygen consumption, measured at submaximal and calculated at supramaximal work. The NA levels increased slowly, up to about 75 % of the maximal oxygen consump tion, thereafter the NA levels increased rapidly. These increases are discussed with respect to increased sympathetic impulse flow, decreased inactivation of the circulating NA, and increased release from the nerve terminals per nerve impulse. At a work load requiring about 75 % or less of the maximal oxygen consumption the mean sympathetic impulse flow seems to be low. At the highest work loads (maximal to supramaximal) a markedly increased sympathetic impulse flow is of major importance for the rapidly increasing NA levels.
The most accepted criterion for confirming attainment of VO(2)max is a plateau in oxygen consumption (VO(2)) at VO(2)max, but its incidence varies.
To compare VO(2)max and VO(2) plateau incidence across various sampling intervals, and to examine predictors of the change in VO(2) (DeltaVO(2)) at VO(2)max.
Sedentary, recreationally-active, and endurance-trained subjects (n = 108, age = 24.2 +/- 6.2 year) completed incremental exercise on the treadmill or cycle ergometer. Gas exchange data were obtained breath-by-breath and time-averaged every 15, 30, and 60 s. VO(2)max attainment was verified with the Taylor et al. (1955) criterion (DeltaVO(2) at VO(2)max < or =2.1 ml kg(-1) min(-1)). Multiple regression was used to examine predictors of DeltaVO(2) at VO(2)max.
VO(2) plateau incidence was higher using breath-by-breath (81%) and 15 (91%) and 30 s time averaging (89%) versus 60 s averaging (59%). Compared to 60 s averaging, VO(2)max was significantly higher (P<0.05) when data were obtained breath-by-breath and with 15 and 30 s time-averaging compared to 60 s sampling. VO(2)max was not related to VO(2) plateau incidence. Respiratory rate was a significant predictor of DeltaVO(2) at VO(2)max in endurance-trained subjects.
More frequent data acquisition revealed higher VO(2)max and incidence of the VO(2) plateau compared to 60 s time averaging. Secondary criteria to verify VO(2)max attainment should not be used, as they do not discern between subjects who do and do not reveal a plateau in VO(2) at VO(2)max.
A young (X = 36.8 years) and an old (X = 52.9 years) group (n = 12) matched for physical fitness performed a graded exercise test at the beginning and after a 4-month physical fitness program consisting of calisthenics, jogging, and recreational activities. The purpose of the study was to determine if there were any differences in response to physical training in the two age groups of similar fitness. Sixteen physiological and four biochemical variables were measured. There was no significant difference in VO2 max between the young and old groups. Also, there were no significant differences between groups for serum total lipids, cholesterol, triglycerides, or glucose levels. The effects of the training program were similar for both the young and old groups.
Five physically active young healthy workers, aged 20-24 yrs, were subjected to runs on a treadmili for 8 h at different relative loads (RLs) i.e. the percentage of maximum aerobic power ([Vdot]o2max)viz. 20,30,40,50, 60 and 70%, in comfortable laboratory conditions to determine the acceptable workload (AWL) for sustained physical activity. The findings have indicated that 35% RL could perhaps be reasonably considered as the AWL. The energy expenditure and the corresponding heart rate at this level of work would be around 18 kJ min (gross) and 110 beats min respectively.
In order to study possible changes in Swedish men between the approximate ages of 19 and 30, 55 men from the Stockholm area were re-examined 11 years after examinations made in connection with compulsory military duty. The most pronounced finding was a 11% increase in body weight accompanied by a 19% increase in waist circumference and a 25–41% increase in skinfold thickness. A 5% increase in work output at heart rate 170 (W
170) was observed but the ratio W
170/weight decreased by 5%. The observed changes were even more pronounced in a subgroup who had a low exercise level in their spare time at the age of 19 as well as 30.
Growth was not quite completed at the age of 19. Of the increase in height amounting to 1.3 cm, 70% was due to growth in tibial length.
Seventy-six workers, aged 21–43 y. drawn from three major steel plants—two located in the eastern and one in the central region of India (referred to as Group A, Group B and Group C respectively)—were studied on the bicycle ergometer to determine their aerobic capacity ([Vdot]O2max), Both the direct and indirect methods were employed, the direct one being used only in the case of the workers in Group C. The mean [Vdot]O2max of these workers was found to be 42·6 cm kg with a standard error of ± 0·71 cm kg min. The highest values were observed among the workers in Group B (mean 47·0± 1·35 (S.E.)cmkg min) who are ethnically distinct and have a high level of customary activity, and the lowest among workers in Group C (mean: 39·0±0·74(S.E.) cmkg min).As expected, the [Vdot]O2max was found to be correlated positively with body weight, and negatively with age in a multiple regression analysis. Furthermore, the active Group B has values for [Vdot]O2max that are significantly higher than those for the other Groups, a difference that is not attributable to weight or age.
This study was designed to determine how aging and individual activity patterns affect females' response to maximal exercise. Two treadmill tests for maximal aerobic power (Vo2 max) were administered to 109 females, ages 10 to 68. Subjects were classified as above or below age group means for Vo2 max reported for Scandinavian and Canadian females. Aging effects on cardiovascular and respiratory variables were minimal within each group until age 50, although there was a significant linear decrement in Vo2 max (L/min) with increasing age for the low fitness group. VE max, oxygen debt, postexercise blood lactate, vital capacity, and maximal breathing capacity were also lower for these women. Aging patterns were similar for both groups for Vo2 max ml/kg times min- minus 1 and ml/kg (LBM) times min- minus 1. Responses to an Activity Questionnaire suggested that habitual levels of activity rather than age per se determines levels of Vo2 max for women in the 20-49 age range.
The energy cost of walking (C
w). and running (C
r), and the maximal O2 consumption (VO2max) were determined in a field study on 17 Pygmies (age 24 years, SD 6; height 160 cm, SD 5; body mass 57.2 kg, SD 4.8) living in the region of Bipindi, Cameroon. TheC
w varied from 112 ml·kg−1·km−1, SD 25 [velocity (ν), 4 km·h−1] to 143 ml·kg−1·km−1, SD 16 (ν, 7 km·h−1). Optimal walking ν was 5 km·h−1. TheC
r was 156 ml·kg−1·km−1, SD 14 (ν, 10 km·h−1) and was constant in the 8–11 km·h−1 speed range. TheVO2max was 33.7 ml·kg−1· min−1, i.e. lower than in other African populations of the same age. TheC
r andC
w were lower than in taller Caucasian endurance runners. These findings, which challenge the theory of physical similarity as applied to animal locomotion, may depend either on the mechanics of locomotion which in Pygmies may be different from that observed in Caucasians, or on a greater mechanical efficiency in Pygmies than in Caucasians. The lowC
r values observed enable Pygmies to reach higher running speeds than would be expected on the basis of theirVO2max.
The aim of the present research was to investigate further the possible r81e of myohemoglobin as an oxygen-store during the initial stage of muscular work. One subject worked intermittently with a work load of 2,520 kpm/min with varied duration of work and rest pauses on a bicycle ergometer. A highly significant difference in the blood lactic acid concentration during the experimental time of 30 min was found, at work with short work periods (10 sec, lactic acid concentration about 10–20 mg per 100 ml) compared with relative long ones (60 sec, lactic acid concentration 110–140 mg per 100 ml). The conclusion was drawn that the first type of work is performed aerobically. The calculated oxygen demand, during the work period of 10 sec, however, does not correspond to the measured oxygen intake. A deficit of about 0.43 1 O2 for each period of work will occur. It was suggested that this amount of 0.43 1 O2 is supplied to the working muscle mainly from oxymyo-hemoglobin. This store function of myohemoglobin is discussed in relation to the present findings and to the results mentioned in the literature.
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Intermittent running on a tread mill at a speed of 20 km/h (12.4 miles/h) is analysed and a comparison between this work and continuous running at the same speed has been done. The present results are in agreement with the assumption that stored oxygen plays an important role for the oxygen supply during short spells of heavy work. When running intermittent 6.67 km in 30 min (effective work 20 min and rest 10 min), a trained subject attained a total O2 uptake of 150 1. With an O2 uptake of 0.4 1/min at rest standing at the tread mill, or 4 1 per 10 min of rest, 146 1 O2 are due to the 20 min of work. The actual uptake at work was only 101 1 and if normal values are assumed during rest pauses, a deficit in oxygen transport of 45 1 arises during the 20 min of actual work. This quantity will be taken up during the 120 rest pauses of 5 sec each. Two thirds of the oxygen demand during the 120 work periods of 10 sec each will accordingly be supplied by oxygen transported with the blood during work, and one third will be covered by a reduction in the available oxygen stores in the muscles, which in turn will be reloaded during the subsequent 5 sec rest periods. Respiratory and circulatory functions at intermittent and continuous running with special reference to maximal values are discussed. Research on intermittent work may open up a new field in work physiology.