The influence of flywheel weight and pedalling frequency on the biomechanics and physiological responses to bicycle exercise†

The physiological, subjective and biomechanical effects of altering flywheel weight and pedalling rate on a Quinton Model 870 bicycle ergometer were studied. Steel plates were added to the flywheel to increase its weight to 35·9 kg with a moment of inertia of 1·65 kg m². A 1·5 kg spoked wheel with a moment of inertia of 0·1 kg m² was used as the light flywheel. Eight subjects pedalled on two separate occasions for 6 min at 40, 50, 60, 70, 80 and 90 r.p.m. with workload levels representing 30 and 60% of their [Vdot]O₂max with each flywheel. Force plate pedals were used to measure the total resultant force on the pedals (F_R ) and the component perpendicular to the crank arm (F_T). A force effectiveness index (FEI) was denned as the average of F_T/F_R over a crank cycle. The result showed no statistically significant change (p<0·05) in [Vdot]O₂, heart rate and rating of perceived exertion of the FEI as a function of flywheel weight except for the [Vdot]O₂ at 50 r.p.m. for the light workload. As the r.p.m. increased from 40 to 90 r.p.m., the FEI decreased from 0·5 to 0·35 with the heavy load and from 0·36 to 0·22 with the light load. Measured physiological, subjective and biomechanical indices did not change significantly with flywheel weight. Increasing the pedalling rate caused a significantly less effective application of forces to the crank arm with only a small change in [Vdot]O₂.     

Aerobic capacity of urban women homemakers in Bombay

Twenty-six healthy women homemakers residing in the metropolitan city of Bombay were studied on a treadmill and a cycle ergometer to determine their aerobic capacity ([Vdot]O₂ max) with a view to evaluating their cardio-respiratory fitness and ascertaining the job-demand-fitness-compatibility in household activities. The [Vdot]O₂ max was found to be significantly higher in treadmill experiments, i.e. 15% in absolute value and 18% in relative value, as compared with that obtained by cycle ergometry (p < 0·001). A much higher difference was observed in values derived from the two methods on the same subjects (i.e. 28% in absolute value and 31% in relative value). Thus, the [Vdot]O₂max obtained from treadmill experiments may be regarded as the maximal aerobic power or the highest oxygen uptake that an individual can attain during exercise, which in the sample of the present study was recorded as 1·901 min ^?1 (33·9 ml kg ^?1 min ^?1). The findings also revealed that age and body weight have a direct influence on [Vdot]O₂max, which was found to be significantly correlated, positively with the latter and negatively with the former (p<0·01 in both cases). The physiological job-demand of household activities seems to be compatible in relation to the [Vdot]O₂max of the homemakers.     

The relationship between heart rate and oxygen uptake during non-steady state exercise

In this study the validity of using heart rate (HR) responses to estimate oxygen uptake ([Vdot]O₂) during varying non-steady state activities was investigated. Dynamic and static exercise engaging large and small muscle masses were studied in four different experiments. In the first experiment, 16 subjects performed an interval test on a cycle ergometer, and 12 subjects performed a field test consisting of various dynamic leg exercises. Simultaneous HR and [Vdot]O₂ measurements were made. Linear regression analyses revealed high correlations between HR and [Vdot]O₂ during both the interval test (r= 0.90±0.07) and the field test (r= 0.94±0.04). In the second experiment, 14 non-wheelchair-bound subjects performed both an interval wheelchair test on a motor driven treadmill, and a wheelchair field test consisting of dynamic and static arm exercise. Significant relationships were found for all subjects during both the interval test (r = 0.91±0.06) and the field test (r= 0.86±0.09). During non-steady state exercise using both arms and legs in a third experiment, contradictory results were found. For 11 of the 15 subjects who performed a field test consisting of various nursing tasks no significant relationship between HR and [Vdot]O₂ was found (r= 0.42±0.16). All tasks required almost the same physiological strain, which induced a small range in data points. In a fourth experiment, the influence of a small data range on the HR-[Vdot]O₂ relationship was investigated: five subjects performed a field test that involved both low and high physiological strain, non-steady state arm and leg exercise. Significant relationships were found for all subjects (r = 0.86±0.04). Although the r-values found in this study were less than under steady state conditions, it can be concluded that [Vdot]O₂ may be estimated from individual HR-[Vdot]O₂ regression lines during non-steady state exercise.     

A new kayak ergometer based on wind resistance

Abstract

An ergometer for kayak paddlers has been developed and used for winter training, measurements of work capacity and maximal oxygen uptake ([Vdot]O₂ max). Force is transmitted from the paddle by means of a wire connected to a flywheel mounted with six 9 × 9cm blades. Resistance, therefore, is based on wind turbulence generated by the flywheel. The mechanical efficiency of the ergometer at 63% (range 48-77) of [Vdot]O₂ max was 17% (range 16-18) (n= 13). The [Vdot]O₂ max was similar during bicycling (median 4·9; range 4·4-5·4l/min), arm cranking (median 4·8; range 4·3-5·11/min), on-water rowing in a kayak (median 4·7; range 4·0-4·91/min) and during rowing the kayak ergometer (median 4·8; range 4·3-5·21/min), (n = 6, p> 0·05). Work capacity during a 5 min ‘all-out’ test was 272 W (range 253–304 W) on the kayak ergometer (n = 17). The use of the ergometer for training helped to increase the aerobic power during arm exercise of Danish paddlers. Before introduction of the ergometer (February 1986), their VO₂ max was 4·6 (range 3·8-5·2) 1/min while 12 months later, it was 50 (range 4·2–5·7) 1/min (n = 14, p < 0·01). The ergometer has thus been found.useful for training and evaluation of work capacity in kayak paddlers.     

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 ([Vdot]O₂), pulmonary ventilation ( [Vdot]O_E), respiratory exchange ratio (R), and rating of perceived exertion (RPE) were determined during the work tasks. HR, [Vdot]O_E, R, and RPE were not significantly different between the shovel and snow pusher. HR averaged (± SD) 141 ± 20bmin_-1 with the shovel, and 142 ± 19 beats-min_-1 with the snow pusher. [Vdot]O₂was 2·1 ± 0·41 min_-1 (63 ± 12% [Vdot]O₂max) in shovelling and 2·6 ± 0·51 min_-1 (75 ± 14% [Vdot]O₂max) 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.     

Metabolic,cardiovascular and spinal strain of a representative fuel replenishment task

The metabolic, cardiovascular and spinal strain of a representative fuel replenishment task for a tank crew were assessed using nine military subjects wearing coveralls in a comfortable ambient climate. The task involved lifting 5 gal jerry cans (weighing 23·4?kg) from the ground to a height representing a tank deck (1·676 m) at a rate of two lifts per minute for 15 min. Oxygen uptake ([Vdot]O₂), minute ventilation ([Vdot]E), heart rate (HR) and intra-abdominal pressure (IAP) were monitored continuously. After 15 min of lifting the mean [Vdot]O₂ was 0·821 min^?1 (S.D. 0·18). This was 27% of the predicted [Vdot]O₂ max. The mean [Vdot]E was 21·81 min^?1 (S.D.4·1) and the HR was 111·3 beats min^?1 (S.D. 17·8). The mean peak IAP was 105·6?mmHg, with 56% of the peak IAPs exceeding 90?Hg. The mean intrasubject coefficient of variation was 10·7% (range 7·2–24·2). In a separate series of 20 consecutive bimanual straight arm vertical lifts of 10?kg at 15 s intervals, the mean intrasubject COV% was 7·2% (range 3·2–11·2%). The replenishment task was considered acceptable in terms of the metabolic and cardiovascular strain. In terms of spinal strain, there may be an unacceptable risk of back injury if the task was normally undertaken as part of a soldier's full-time occupation over many years     

Permissible loads based on energy expenditure measurements

The literature is reviewed and, based on this, it is suggested that the upper general tolerance limit over an 8-hour work day, consisting of mixed physical work, including handling operations, is approximately 30–35% [Vdot]O₂ max (on bicycle legwork or treadmill). Therefore, the individual tasks must be adjusted to a metabolic level not exceeding 30–35% [Vdot]O₂ max in the majority of the labour force or may be more realistic in specific groups within the labour force (young/ old, male/female). The following metabolic values are suggested (1 [Vdot]O₂ ): males <40 years: 0·7males>40 years: 0·6; females < 40 years: 0·6; females >40 years: 0·5. It is important to notice that even with a metabolic rate below 30–35% [Vdot]O₂ max it is possible that local overstrain and/ or fatigue in the back muscles during, for example, manual handling operations of long duration can occur     

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.     

The Aerobic and Anaerobic Components of Work during Submaximal Exercise on a Bicycle Ergometer

Abstract

Inter-subject variability of oxygen intake ([Vdot]O₂)n relation to the anaerobic component of work has been investigated intensely on two healthy subjects and extensively on two groups of young and older men during work on an upright, stationary bicycle ergometer.

Significant differences (p<0·001) in [Vdot]O₂ were shown to exist between the two groups of subjects and the healthy men at the higher work-loads which could not be eliminated entirely by correction for body weight. The residual variation of [Vdot]O₂ on work-load was shown to be a consequence of the variation of anaerobic component of exercise. During work on a bicycle ergometer at exercise above about 50% [Vdot] O₂ max this should be taken into account if a valid assessment of energy expenditure is to be made.     

Interrelationships of respiratory variables of coal miners during work

Abstract

The respiratory responses of expiratory volume ([Vdot] _E), respiratory frequency (f _R), oxygen consumption ([Vdot] O₂), and carbon dioxide elimination ( [Vdot]CO₂) were measured for coal miners while they were performing a variety of work tasks (walking, carrying, shovelling, cranking and running). Because of the difficulties in relating the respiratory variables to external work rate and a close dependence of the respiratory responses on metabolic activity, oxygen consumption was chosen as an independent variable in the predictors for pulmonary ventilation, respiration frequency, and carbon dioxide elimination. It was necessary to use nonlinear equations for [Vdot] _E and [Vdot]Co₂ owing to exercise hyperpnoea above the anaerobic threshold.f _R did not correlate well with [Vdot]O₂ or any of the other respiratory variables. The relationship between [Vdot]_E and [Vdot]CO₂ was linear.     

Critical power as a measure of physical work capacity and anaerobic threshold

Monod and Scherrer (1965) showed that there was a linear relation between the maximal work and the maximal time over which the work was performed until the onset of local muscular exhaustion. This linear relation could be expressed by the equation: W _lim =a+bT _lim, where maximal work (W_lim) was thought to result from the use of an energy reserve (a) and an energy reconstitution whose maximal rate was (b) We have extended this concept to total body work (bicycle ergometer). Eight male and eight female college students underwent exercise tests at 400, 350, 300,275 and 300,250,200,175 W respectively, to the onset of fatigue. The regression analysis revealed that the linearity of individual plots was found to be 0-982<R ²<0 998 (p<0 01). Experimental results indicated that the maximal energy reconstitution rate (b) was correlated with the onset of anaerobic threshold (AT) as determined by the gas exchange method (r = 0 928, p <0 01). Furthermore, the sum of (a) and (b) (energy reserve and maximal rate of energy reconstitution) was found to be highly correlated with [Vdot]O₂ max (r = 0 956, p < 0001) and the regression equation: [Vdot]O₂max (1/min) = 0 00795 x [a + b] + 0 114 could be used to predict [Vdot]O₂max with a SEE of 0-241/min.     

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     

Evaluation of metabolism from heart rate in industrial work

Oxygen consumption ([Vdot]O₂) and heart rate (HR) were measured in 40 men performing different types of industrial work in eight factories

A [Vdot]O₂-HR relationship was established for each subject using an exercise test on a bicycle ergometer. HR measured during the industrial work was entered in the [Vdot]O₂-HR function, and [Vdot]O₂ thus calculated. A systematic comparison of the calculated [Vdot]O₂ (c[Vdot]O₂) with the actual measured [Vdot]O₂ (m[Vdot]O₂), showed that c[Vdot]O₂ significantly overestimated the [Vdot]O₂ during industrial work. The degree of overestimation was related to the type of work performed. The static muscular activity and the non-steady-state characteristics of the work were responsible for most of the overestimation

A more reliable technique for estimating metabolic rate is to make simultaneous measurements of [Vdot]O₂ and HR at different times during the work day and then from these recordings establish a function: [Vdot]O₂=f(HR). Continuous HR recordings can then be used to calculate a more accurate estimate of the metabolic rate.     

Metabolic and respiratory profile of the upper limit for prolonged exercise in man

For high-intensity cycling, power (P) can be well described as a hyperbolic function of tolerable work duration (t): P=(W'/t) + P _LL W' is a constant and P _LL is the lower limit (asymptote) for P which is shown to occur at an O₂ uptake ([Vdot]O₂) lying above the estimated threshold for sustained blood [lactate] increase (Θ_Iac) but below the maximum [Vdot]O₂ ([Vdot]O₂max) obtained during incremental cycling. This relation suggests that, above P _LL, only a certain amount of work (W') can be accomplished regardless of its rate of performance, with [Vdot]O₂ max being attained at fatigue. Hence, P _LL defines a point of discontinuity in the [Vdot]O₂-P relation for supra-Θ_Iac exercise. In order to determine the factors responsible for the continued increase in [Vdot]O₂ (to the maximum fatiguing value) at power outputs >P _LL, we documented the temporal profiles of metabolic (rectal temperature; blood [lactate], [pyruvate], [norepinephrine], [epinephrine]) and respiratory ([Vdot]_E; [Vdot]O₂; [Vdot]CO₂; blood pH, PCO₂, [HCO₃ ^?]) responses to constant-load cycling in eight healthy males at P _LL (24 min) and slightly above P _LL (to exhaustion, i.e. < 24 min). [Vdot]O₂ manifested a delayed steady state at P _LL, despite catecholamine levels and core temperature continuing to increase throughout; blood [lactate] and pH plateaued, however. In contrast, [Vdot]O₂ continued to increase slowly for the duration of the exercise > P _LL and attained [Vdot]O₂max. The response patterns at P _LL, and > P _LL suggest that the slow phase of the [Vdot]O₂ response is best correlated with the temporal profile of blood [lactate], and hence the site and route of metabolism of this variable may play a major role in the [Vdot]O₂ kinetics for high-intensity exercise.     

Energy cost of backpacking in heavy boots

Previous studies have investigated the oxygen cost ([Vdot]0₂) of increasing boot weight during unloaded walking or running, and have shown that for each 100 g increase in weight of footwear there is a 0·7-1·0% increase in [Vdot]O₂ In reality (except in athletic events) the use of heavy footwear is associated with load carriage, usually backpacking. We therefore investigated the effects of increasing boot weight by 5% of body weight on the [Vdot]0₂ of backpacking a load amounting to 35% of the body-weight in five healthy young males who walked at 4·5 km/hour (0% grade) on a motor-driven treadmill. The results indicated a mean increase of 0·96% in [Vdot]0₂ whilst backpacking for each 100thinsp;-g increase in boot weight. In contrast the oxygen cost of increasing the backpack load was only 0·15% indicating that it was 6·4 times more expensive to carry weight on the feet as compared to the back. It is concluded that the relation between boot weight and oxygen cost, previously developed for unloaded walking and running, can reasonably be extended to include heavier boots and backpacking.     

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.     

Metabolic and perceptual responses while carrying external loads on the head and by yoke

Abstract

The purpose of this study was to determine the metabolic efficiency and perceptual acceptability of transporting external loads on the head and by yoke. Ten young males (24·2 ±3·9 years) of average physical fitness ([Vdot]O_2max=49·8 ± 6·5ml kg^-1 min^-1) walked for 6min on a level motor-driven treadmill at 53·6, 73·8 and 93·9m min^-1. Subsequently, all subjects carried external loads (11·6, 16·1 and 20·6 kg) at the same speeds using the headpack (HP), transverse yoke (TY) and frontal yoke (FY) modes of load carriage. Measurements were obtained for oxygen uptake ([Vdot]O₂ l min^-1), local ratings of perceived exertion (RPE-L) and the overall perceived exertion (RPE-O). The [Vdot]O₂ was used in the computation of the metabolic efficiency ([Vdot]O₂ ml kg total weight^-1 min^-1).

Significant main effects (mode, load and speed) and three interaction effects (mode × load, mode × speed and load × speed) were obtained for metabolic efficiency. Scheffé post hoc analysis revealed that the metabolic efficiency for the TY and HP were greater than the FY while transporting the 16·1 and 20·6kg loads at all walking speeds (p <0·05). No significant loss in metabolic efficiency was found while carrying the 20·6kg load at 53·6 m min^-1. At 93·9 m min^-1, all external loads transported were associated with a loss in metabolic efficiency. The RPE-L for the HP was lower than the FY (p < 0·05). Both the RPE-0 and RPE-L increased as the walking speeds and external loads were increased. The findings suggest that load transportation using the FY system is both physiologically and perceptually unacceptable.     

Aerobic capacity of severely disabled Indians

To study the oxygen uptake capacity, the arm crank ergometer test was administered at three different loads, 25,37·5 and 50 W, on seven severely disabled subjects, and their cardiorespiratory responses were compared to that of nine normal subjects (work loads, 25, 50 and 75 W). Values of [Vdot]O₂ of the disabled subjects corresponding to heart rates of 150 and 180 beats min^?1 were significantly lower than those of the normal subjects, when expressed in l min^?1, but disappear when the results are expressed in ml kg min^?1. The observations indicate a reduced work capacity and a capacity for increasing the stroke volume of the disabled subjects.     

The ‘Oxylog’: an evaluation

Abstract

The Oxylog is a portable instrument designed to measure the oxygen consumption ([Vdot]0₂) an ambulatory subject. Steady-state measurements have been made, using an Oxylog, of inspiratory volume ( [Vdot]₁) [Vdot]0₂ during bicycle ergometer exercise at work rates ranging from 30 to 150 W. These measurements have been compared with simultaneous measurements of expiratory volume ([Vdot] _E) and [Vdot]O₂ made using a dry gas meter and mass spectrometer.

Four experiments were conducted, during which a total of 433 comparative measurements were made. In two experiments the Oxylog significantly underestimated [Vdot]O₂ (by 4-4 and 5-6%). Averaging over the four experiments, however, the underestimate reduced to 1-5%, which could be accounted for by a respiratory exchange ratio of approximately 0-9. There was, overall, no significant difference between [Vdot] ₁ and [Vdot] _E.

It is concluded that the Oxylog is sufficiently accurate for the reliable determination of [Vdot]0₂ and of energy expenditure under field conditions.