Cardiac frequency throughout a working shift in coal miners

Despite the ever-increasing mechanization of industrial activities, coal mining still remains a physically demanding occupation as it is not always possible to extensively mechanize the extraction process. To estimate the physical effort necessary to sustain coal mining activities in a poorly-mechanized mine, cardiac frequency (?/_c) was measured throughout the working shift with a Sport-Tester PE3000 (Polar Electro OY. Finland) in a representative sample of 73 Asturian miners engaged in a full spectrum of underground work. The mean ± SD of the overall?/_c values measured in miners working at the coal face (Group 1, 33 subjects, mean age 32·7 years, age range 21–48 years R was 106·5 ± 18·2 beats min^?1. In other miners (Group 2, 40 subjects, mean age 34·6 years, age range 23–48 years) corresponding figures were 1031 ±177 beats-min_?1 (p<0·05). Subjects' average working shift?_c Lbeats. Min^?1) was not related to age, measured (treadmill) VO₂ max nor VO₂ max.kg body weight^?1, while average working-shift? _c (%? _c max) was weakly related to age (r = 0·396, p<0·05), VO₂ max (r equals; 0·295, p < 0·05) and VO₂max.kg body weight^?1 (r= 0·352, p<0·05). Working-shift peak? _c (beats · min^?1) was negatively related to age (r = 0·334, p < 0·05). Our study has provided the distribution of the overall ? _c values likely to be found in subjects working in these poorly-mechanized mines. However, average working-shift ? _c differs considerably from subject to subject and is largely unpredictable.     

Metabolic and cardiovascular responses to exercise with caffeine

The effect of caffeine on circulation and metabolism was studied during a discontinuous maximal oxygen uptake (VO₂ max) test on a bicycle ergometer. Eight male subjects were chosen for their minimal use of caffeine of which six normally did not ingest caffeinated beverages. Two caffeinated and two decaffeinated (control) trials were administered to each subject following double-blind and counterbalanced testing procedures. One hour before exercise, subjects ingested decaffeinated coffee with or without 350 mg of caffeine anhydrous added. Cardiac output (Q) was measured by a C0₂ rebreathing technique. Compared to control trials, caffeine increased the VO₂ max by an average of 140ml min?¹ (p <0-0·5)l. In addition, during caffeine trials, the average maximal heart rate (HR max) was elevated by 5 beats min^?1 (p<0·01). There were no other statistically significant changes in metabolic (VO₂ and R) and cardiovascular (Q, HR, SV and (a-v) 0₂ diff) variables during either submaximal or maximal exercise. Performance, as measured by total exercise time on the VO₂ max test, was not significantly different (p>0·05). It was concluded that caffeine has a small physiological but a statistically significant effect on VQ₂ max and HR max. During submaximal exercise, caffeine did not significantly effect the cardiovascular system.     

Aerobic Capacity of Steel Workers in India

Abstract

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 cm³ kg^?1 with a standard error of ± 0·71 cm³ kg^?1 min^?1. The highest values were observed among the workers in Group B (mean 47·0± 1·35 (S.E.)cm³kg^?1 min^?1) 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.) cm³kg^?1 min^?1).

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.     

The relation between cycling time to exhaustion and anaerobic threshold

Abstract

This study investigated whether the anaerobic threshold (AnT) could be used to predict prolonged work capacity measured as cycling time to exhaustion (= endurance time) and which factors, in addition to relative exercise intensity, could explain variation in endurance time. Theoretical exercise intensities corresponding to certain endurance times were also calculated. The hyperbolic and exponential functions between cycling time and relative work rate (WR[%]), as well as between cyling time and relative oxygen uptake ([Vdot]O₂[%]) were fitted to the pooled data (n = 45) of 17 subjects. The WR(%) and [Vdot]O₂ (%) were expressed as a percentage of the subject's own AnT- and maximum -values. At WR corresponding to AnT (i.e., 70% of WR_max) an average subject could cycle 60 min according to both AnT- or maximum-related exponential function. When prediction was done for an endurance time of 4 h, the AnT-related exponential function gave 2·9%-units ( = 11 W or ～0·15 O₂1 · min^?1) lower intensity level (51% of WR_max than the maximum-related function (54% of WR_max). The WR(%) alone explained 54% and 70% of the variation in endurance time of the AnT-related and maximum-related exponential functions, respectively. Muscle fibre composition and initial blood lactate or relative muscle glycogen depletion (change in muscle glycogen as percentage) increased significantly the explanatory power of these models. The differences between the observed and expected exercise times correlated with blood lactate accumulation (r = ?0·42; p < 0·01), muscle fibre composition (r = 0·33; p < 0·05) and relative muscle glycogen depletion (r = 0·67; p < 0·01). It was concluded that the capacity for prolonged work measured as cycling time to exhaustion can be estimated by AnT-related power output, and that the exponential function model is the most suitable. Prediction power of the model can be improved by multiple regressions including muscle fibre composition, initial blood lactate level and relative muscle glycogen depletion.     

Development of role-related minimum cardiorespiratory fitness standards for firefighters and commanders

A minimum cardiorespiratory fitness standard was derived for firefighters following a metabolic demands analysis. Design and minimal acceptable performance of generic firefighting task simulations (i.e. hose running, casualty evacuation, stair climb, equipment carry, wild-land fire) were endorsed by a panel of operationally experienced experts. Sixty-two UK firefighters completed these tasks wearing a standard protective firefighting ensemble while being monitored for peak steady-state metabolic demand and cardiovascular strain. Four tasks, endorsed as valid operational simulations by ≥90% of participants (excluding wild-land fire; 84%), were deemed to be a sufficiently valid and reliable basis for a fitness standard. These tasks elicited an average peak steady-state metabolic cost of 38.1 ± 7.8 ml kg^?1 min^?1. It is estimated that healthy adults can sustain the total duration of these tasks (~16 min) at ≤90% maximum oxygen uptake and a cardiorespiratory fitness standard of ≥42.3 ml kg^?1 min^?1 would be required to sustain work.

Practitioner Summary: A cardiorespiratory fitness standard for firefighters of ≥42.3 ml kg^?1 min^?1 was derived from monitoring minimum acceptable performance of essential tasks. This study supports the implementation of a routine assessment of this fitness standard for all UK operational firefighters, to ensure safe physical preparedness for occupational performance.     

Effects of dynamic,static and combined work on heart rate and oxygen consumption

The effects upon heart rate and oxygen consumption of muscular exercises including simultaneous dynamic and static contractions were studied in three male subjects. Dynamic work consisted of walking at four speeds (0·56, 0·83, 1·11, 1·39 m s^?) on a horizontal treadmill; static work consisted of pushing against, pulling and holding 6, 9, 12, 18 and 24?kg; combined work associated walking with each one of the forms of static work. Physiological load is expressed in terms of cardiac cost (ΔHR) and oxygen cost (Δ[Vdot]_o2). The physiological cost of combined work increases with both the walking speed and the static load. For each parameter (HR and [Vdot]_o2) the extra-cost of combined work has been determined by computing the difference between the cost of combined work and the sum of the costs observed during static and dynamic exercises separately performed. The paired t-test shows significant differences for all of the walking-pushing tests, but only for 8 pulling tests and 2 holding tests. Linear relationships are observed between the oxygen extra-cost and load when walking at 0·56 or 0·83 ms^?1, with correlation coefficients statistically significant for pushing and pulling (p < 0·01) but not significant for holding tests. The present results show that, when the static work is combined with walking, the physiological response varies with the type of static work considered.     

Fitness of teenage boys in Poland

Average values for a variety of anthropometric and physiological parameters have been obtained for a representative group (N = 485) of Polish students of professional schools ranging from 14-18 y age. The mean values of height, approximately 175 cm, weight 66 kg and V _O2max, 3·25 l_O2; min^?1 or 48·3cm³kg^?1 min"1 or 59·2cm³kgFFB^?1min^?1, were a little higher than the average in terms of physical fitness

According to assessments for ergonomic use, the present investigations confirmed that Polish Anthropometric Standards could be applied to the design of new workplaces by using the upper limits of these standards. The optimal level of average work load for new workers is a little above 21 kJ min^?1

During pre-employment and periodical medical examinations of adolescents the Vitalograph spirometer can be used because predicted values of FVC and FEV_1·0 for this spirometer have been calculated.     

Estimated aerobic performance and energy cost of severe exercise of 24 h duration

Abstract

The maximal aerobic performance ([Vdot]O₂max) and energy cost of running at various speeds of two ultra-distance athletes were measured in the laboratory on a motor driven treadmill and the results related to observations made during a 24 h race. The athletes finished 1st and 2nd in the event and covered distances of 251·46 km and 234·56 km respectively during the 24 h period. From the measurements in the laboratory it was calculated that the average speeds sustained by the athletes during the competition were equivalent to an O₂ cost of 36·4 ml kg^?1 min^?1 and 35·3 ml kg^?1 min^?1 which represented approximately 50% of their [Vdot]O₂max. During the race the winner expended an estimated 77,829 kJ (18.595 kcal) which is three times the highest recorded value in the most severe industrial work. By the nature of the activity this figure must be regarded as at or near the upper limit of sustainable energy expenditure by man during a complete uninterrupted 24 h circadian cycle.     

The Effect of Posture on the Running Speed of Skiing

Abstract

These experiments were performed at the Syowa Station in Antarctica (69°00'S, 39° 35'E) where a straight ski course was constructed (length 100m. gradient 12°). The conditions were as follows; wind velocity: 0-0·5ms^?1, temperature: ? 25°C, snow temperature: ?29·5°C.snow density: 0·309 gcm^?3. Running speed was measured by a coil-magnet system. The subject with a small magnet fixed on one leg ran closely down past the coils placed every 5m along the course. Two healthy members of the Japanese Antarctic Research Expedition who were well-trained skiers acted as subjects. Running speed was measured in three different postural conditions (a) standing, (b) egg-shaped, (c) starting in the egg-shaped posture and then standing erect in the latter half of the course. Velocity was measured throughout the course and the following results were obtained: velocities at the final section of the coils, which were placed 65m from the start point, were as follows for each postural condition: Subject KW; (a) standing, 7·6ms^?1 (b) egg-shaped, 8·6ms^?1 (c) egg-shaped followed by standing erect, 8·2ms^?1. Subject B; (a) 7·8ms^?1, (b) 8·9ms^?1, (c) 8·4ms^?1. The friction between the ski and snow was calculated as about 0·13 for all conditions. It was concluded that postural difference may have a considerable and clear-cut effect on running speed even when the skiing speed is rather low.     

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO_2max) of 4.4 ± 0.3 l/min (mean ± SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter ‘rescued’ six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O₂ uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO_2max and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5–9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 ± 3 mmol/l. The peak oxygen uptake was 3.7 ± 0.5 l/min (84% of the VO_2max) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO_2max in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO_2max in absolute values and the working technique used. A minimum VO_2max of 4 l/min for firefighters was recommended.     

Air management and physiological responses during simulated firefighting tasks in a high-rise structure

Air consumption, oxygen uptake (VO₂), carbon dioxide output (VCO₂) and respiratory exchange ratio (RER = VCO₂/VO₂) were measured directly from the self-contained breathing apparatus (SCBA) as 36 professional firefighters (three women) completed scenarios of high-rise stair climbing and fifth floor search and rescue. During stair climbing VO₂ was 75 ± 8% VO_2max (mean ± SD), RER = 1.10 ± 0.10, and heart rate = 91 ± 3% maximum (based on maximum treadmill data). Firefighters stopped climbing on consuming 55% of the air cylinder then descended. In the fifth floor search and rescue VO₂ was slightly lower than stair climbing but RER remained elevated (1.13 ± 0.12) reflecting high anaerobic metabolism. The first low air alarm sounded, indicating 25% of the air remaining in a “30-min cylinder”, during the stair climb at 8 min with 19 of 36 sounding before 12 min. Aggressive air management strategies are required for safety in high-rise firefighting.     

Muscular,cardiorespiratory and thermal strain of mast and pole workers

This field study evaluated the level of muscular, cardiorespiratory and thermal strain of mast and pole workers. We measured the muscular strain using electromyography (EMG), expressed as a percentage in relation to maximal EMG activity (%MEMG). Oxygen consumption (VO₂) was indirectly estimated from HR measured during work and expressed as a percentage of maximum VO₂ (%VO₂max). Skin and deep body temperatures were measured to quantify thermal strain. The highest average muscular strain was found in the wrist flexor (24 ± 1.5%MEMG) and extensor (21 ± 1.0%MEMG) muscles, exceeding the recommendation of 14%MEMG. Average cardiorespiratory strain was 48 ± 3%VO₂max. Nearly half (40%) of the participants exceeded the recommended 50%VO₂max level. The core body temperature varied between 36.8°C and 37.6°C and mean skin temperature between 28.6°C and 33.4°C indicating possible occasional superficial cooling. Both muscular and cardiorespiratory strain may pose a risk of local and systemic overloading and thus reduced work efficiency. Thermal strain remained at a tolerable level.     

Heart-rate response to forest harvesting work in the south-eastern United States during summer

Abstract

The physiological workload of forest harvesting workers during summer in the south-eastern United States was evaluated by measuring work heart-rate response. The harvesting tasks considered were chainsaw felling, cable skidding, bucking and trimming at the landing, knuckle-boom loader operation, feller-buncher operation and grapple skidding. VO₂ max of the workers ranged from 28 to 53 ml min^?1kg^?1. The WBGT ranged from 20 to 344°C during data collection. The task time-weighed, age-corrected, percent maximum heart-rate response ranged from 42-5 to 69 2°. The data indicate that the manual and semi-mechanized tasks are potentially stressful and that hotter environmental conditions increase the likelihood of higher heart-rate responses. No relationship was found between heart-rate response and three measures of static muscle strength.     

Aerobic performance of Special Operations Forces personnel after a prolonged submarine deployment

The US Navy's Sea, Air and Land Special Operations Forces personnel (SEALs) perform a physically demanding job that requires them to maintain fitness levels equivalent to elite athletes. As some missions require SEALs to be deployed aboard submarines for extended periods of time, the prolonged confinement could lead to deconditioning and impaired mission-related performance. The objective of this field study was to quantify changes in aerobic performance of SEAL personnel following a 33-day submarine deployment. Two age-matched groups of SEALs, a non-deployed SEAL team (NDST, n= 9) and a deployed SEAL team (DST, n= 10), performed two 12-min runs for distance (Cooper tests) 5 days apart pre-deployment and one Cooper test post-deployment. Subjects wore a Polar Vantage NV^TM heart rate (HR) monitor during the tests to record exercise and recovery HR. Variables calculated from the HR profiles included mean exercise heart rate (HR_mean), maximum exercise heart rate (HR_max), the initial slope of the HR recovery curve (HR_reslope) and HR recovery time (HR_rectime). The second pre-deployment test (which was used in the comparison with the post-deployment test) showed a 2% mean increase in the distance achieved compared with the first (n= 18, p< 0.05) with no difference in HR_mean, HR_max, HR_reslope and HR_rectime. The test-retest correlation coefficient and 95% limits of agreement for the Cooper tests were 0.79 (p< 0.001) and ?68.6±267.5 m, respectively. For the NDST there were no changes in any of the HR measures or the distance run between the pre- and post-deployment tests. When individual running performances were expressed as a percentage change in the distance run between the pre- and post-deployment tests, the DST performed significantly worse than the NDST (p< 0.01). The DST showed a 7% mean decrement in the distance run following deployment (p< 0.01). The decrement in performance of the DST was not associated with any changes in HRmean or HRmax; however, there was a 17% decrease in the HR_recslope (p< 0.05) and a 47% increase in HR_rectime following the deployment (p< 0.05). In conclusion, prolonged confinement aboard a submarine compromises the aerobic performance of SEAL personnel. The resulting deconditioning could influence mission success.     

The energy cost and heart-rate response of trained and untrained subjects walking and running in shoes and boots

Abstract

To determine the difference in the energy cost of walking and running in a lightweight athletic shoe and a heavier boot, fourteen male subjects (six trained and eight untrained) has their oxygen uptake ([Vdot]O₂) measured while walking and running on a treadmill. They wore each type of footwear, athletic shoes of the subjects' choice (average weight per pair = 616 g) and leather military boots (average weight per pair = 1776g), at three walking speeds (4·0, 5·6 and 7·3 km hour^?1) and three running speeds (8·9, 10·5 and 12·1 km hour^?1). The trials for running were repeated at the same three speeds with the subjects wearing shoes and these shoes plus lead weights. The weight of the shoes plus the lead weights was equal to the weight of the subjects' boots. The [Vdot]O₂values with boots were significantly (p < 0·05) higher (5·9?10·2%) at all speeds, except the slowest walk, 4·0 km hour^?1Also, [Vdot]O₂with shoes plus lead weights were significantly (p<0·05) higher than shoes alone. Weight alone appeared to account for 48-70% of the added energy cost of wearing boots. The relative energy cost ([Vdot]O₂, ml kg^?1?) of trained and untrained subjects were the same at all speeds. These data indicate that energy expenditure is increased by wearing boots. A large portion of this increase may be attributed to weight of footwear. In addition, the increased energy cost of locomotion with boots appears to place a limiting stress on untrained subjects.     

The effect of aerodynamic handlebars on oxygen consumption while cycling at a constant speed

Abstract

In this study, the oxygen consumption ([Vdot]O₂) of bicycling was measured at a fixed speed (40 km·h^?1on level terrain, with normal and aerodynamic handlebars using a Douglas bag collection system. Eleven elite (USCF category I or 2) men cyclists age 24 to 40 years (X¯=28·5, SD±4·6) performed four consecutive (two with each bar in alternating order) steady state rides at 40 km· h^?1over a 4 km flat course (same direction each trial). Expired gases were collected in a 1501 Douglas bag attached to a following vehicle during the last 45 s (approx. 0·5 km) of each trial. A repeated measures analysis of variance revealed a significant (p<0·02) handlebar effect. Specifically, [Vdot]O₂was 2% lower under the aerodynamic handlebar treatment (X¯=4·26, SD±0·36 1 min^?1when compared with that of the normal handlebar treatment (X¯=4·34, SD±0·35 1 min^?1The results of this study demonstrate that the reported aerodynamic advantage of the aerodynamic handlebars produces a small but significant reduction in the [Vdot]O₂of bicycling at 40 km·h^?1     

Sun-stimulated chlorophyll fluorescence 2: Impact of atmospheric properties

Abstract

The Sun-stimulated chlorophyll fluorescence is a small but significant property of phytoplankton which can be detected using remote-sensing techniques. Besides the influence of oceanic properties, chlorophyll fluorescence is masked by atmospheric extinction. While an increase in chlorophyll concentration of 1 mg/m³ causes an increase in the upwelling radiances of about 0·03Wm^?2sr^?1 μm^?1 just above the water surface and due to the chlorophyll fluorescence, the upward radiances measured at λ_F = 685nm and at the top of the atmosphere ranges from 8 to 20Wm^?2sr^?1 μm^?1 for realistic atmospheric turbidity variations and a solar zenith distance of Θ_s = 50·7°. Additionally, the fluorescence, peaking at λ_F = 685nm with a half-width of about 10 nm, is reduced by the absorption of O₂ and H₂O. However, the fluorescence signal is nearly unaffected, when wavelengths λ≥686nm are exluded and a spectral interval of Δλ_F = 5nm is used for the radiance measurements.     

Self-paced hard work comparing men and women

Six fit male subjects (23 years, 171 cm, 67 kg, maximal V?O₂ = 2.25mmol kg^?1 min^?1 (50.3ml kg^?1min^?1)) and six fit female subjects (22 years, 163 cm, 57 kg, maximal V?O₂= l.83mmol kg^?1 min^?1(41.1 mlkg^?1 min^?1)) performed self-paced hard work while walking over four different terrains carrying no external load, 10 kg and 20 kg. Time on each course for individual subjects was used to determine speed and energy expenditure; heart rate was recorded as each subject completed each course. Walking speed and energy expenditure of the males were found to be significantly greater (p< 005) than those of the females overall terrains (blacktop road, 1.6 km; dirt road, 1.8 km; light brush, 1.4 km; and heavy brush, 1.3 km) and for each load carriage condition. Relative energy expenditures of the males and females for all conditions were very similar(p>0.05) and remarkably constant at a value close to 45% V?O₂max, These data indicate that the voluntary hard work rate is dependent upon maximal aerobic power. The best predictor of speed for self-paced hard work of males and females for 1 to 2 hours in duration appears to be based on 45% of maximal aerobic power.     

The effect of monomolecular surface films on the microwave brightness temperature of the sea surface

Abstract

Airborne microwave radiometer measurements at 1·43 and 2·65 GHz over a sea surface covered with a monomolecular oleyl alcohol surface film and over adjacent slick sea surfaces are presented. The measurements show that at 2·65 GHz the brightness temperature T _B is not affected by the slick, while at 1·43 GHz it drops from 93 K to a minimum value of almost O K. This implies that at 1·43 GHz the emissivity of the slick-covered sea surface is extremely small, similar to a metallic layer, and that this resonant-type phenomenon is confined to a narrow frequency band of width δ?/ ?<0·6.

The theoretical implications of these experimental findings are discussed in the framework of the Debye relaxation theory of polar liquids. It is conjectured that a thin layer of water molecules polarized by the surface film gives rise to an anomalous dispersion, which causes the large decrease in brightness temperature at 1·43 GHz.

The modulus of the relative dielectric constant ε? is estimated to be ≥ 5·2 × 10^?4 and the thickness of the emitting layer ≤1·9 × 10^?4 m for 1·43 GHz. Furthermore, the film-induced surface activation energy is calculated to be 9·18 × 10^?21 J. These values seem reasonable in the light of the theories on the physicochemical structure of surface layers.     

Sweat distribution and perceived wetness across the human foot: the effect of shoes and exercise intensity

Abstract

This study investigates foot sweat distribution with and without shoes and the relationship between foot sweat distribution and perceived wetness to enhance guidance for footwear design. Fourteen females performed low-intensity running with nude feet and low- and high-intensity running with shoes (55%VO_2max and 75%VO_2max, respectively) on separate occasions. Right foot sweat rates were measured at 14 regions using absorbent material applied during the last 5?min of each work intensity. Perceptual responses were recorded for the body, foot and four foot regions. Foot sweat production was 22% greater nude (p?<?.001) and with shoes did not increase with exercise intensity (p?=?.14). Highest sweat rates were observed at the medial ankle and dorsal regions; lowest sweat rates at the toes. Perceptions of wetness and foot discomfort did not correspond with regions of high sweat production or low skin temperature but rather seemed dominated by tactile interactions caused by foot movement within the shoe.

Practitioner summary: This study provides a detailed view of foot sweat distribution for female runners with and without shoes, providing important guidance for sock and footwear design. Importantly, perceptions of wetness and foot discomfort did not correspond with areas of high sweat production. Instead tactile interactions between the foot, sock/shoe play an important role.

Abbreviations: VO_2max: maximal oxygen consumption; HR: heart rate; RH: relative humidity; GSL: gross sweat loss; Nude-I1: without socks and shoes, low intensity running; Shod-I1: with socks and shoes, low intensity running; Shod-I2: with socks and shoes, high intensity running