EP1900398A1

EP1900398A1 - Cycle ergometer

Info

Publication number: EP1900398A1
Application number: EP06425627A
Authority: EP
Inventors: Aldo Sassi
Original assignee: SPORT SERVICE MAPEI Srl
Current assignee: SPORT SERVICE MAPEI Srl
Priority date: 2006-09-12
Filing date: 2006-09-12
Publication date: 2008-03-19
Anticipated expiration: 2026-09-12
Also published as: EP1900398B1; DE602006011160D1; ATE451956T1

Abstract

Eccentric cycle ergometer comprising an actual ergometer (1) and a bicycle (10), wherein said ergometer (1) transmits movement via a cogged belt (6) to a crown wheel (8) mounted in line with the rear hub of the bicycle, so that the transmission of the movement to the crown wheel (11) takes place via the chain (12) of the actual bicycle, which is wound on said crown wheel (12). The cycle ergometer also comprises a control panel (20) connected to a power unit (21), said control panel (20) being provided with a touch screen (22) whereby it is possible to set any one of the following operating modes:
constant rate, constant power, constant torque.

Description

The object of the present invention is a cycle ergometer, in particular an eccentric cycle ergometer.

Introduction

Muscle contraction in which the muscle is forcedly elongated by external forces that act thereon, even though the muscle is stimulated to contract, is defined as eccentric. In the normal action of pedalling it is generally considered that there are no eccentric contractions in the lower limbs, despite the fact that contractions of this type have already been demonstrated in the gastrocnemius (Gregor et al., 1987). The mode of eccentric contraction (also known as negative contraction) in the pedalling can be emphasised by means of "eccentric" cycle ergometers (or more generally ergometers), defined in this way because the direction of rotation of the pedals therein is inverted in relation to the normal direction and the subject pedalling exerts his or her force in such a way as to oppose resistance to this rotation.
Eccentric muscle contraction is characterised by a higher metabolic efficiency than that of concentric contraction (in which the muscle shortens during the contraction phase). During eccentric pedalling this translates into a considerable reduction in the consumption of oxygen on a par with the mechanical power developed by the subject (Asmussen, 1953; LaStayo et al., 1999). This special feature appears to be particularly promising in training the elderly or those suffering from cardiovascular disease as, compared to the concentric exercise mode, it allows the mechanical workload to be increased significantly (and hence stimulation of the locomotor system) in relation to the cardiovascular workload (LaStayo et al., 1999; Meyer et al., 2003). Various studies aimed at analysing the benefits of training protocols based on eccentric pedalling have already been published in this area (Chung et al., 1999; LaStayo et al., 1999; Meyer et al., 2003).
In the specific area of cycling, the studies on the effects of training carried out by pedalling in eccentric mode are only at the beginning and will represent an interesting area of investigation for coming years, with possible implications for the habits and methods of training currently adopted.
Growing interest in the possible use of the eccentric mode of pedalling, both in medicine and rehabilitation and sport, has persuaded us to create a type of eccentric ergometer which could better fulfil the needs of physical exercise and training based on eccentric pedalling compared to the possibilities provided by ergometers produced to date or proposed by scientific literature.

State of the art

The first studies on eccentric pedalling were carried out by pedalling downhill on a treadmill, with inversion of the movements of the pedals (Asmussen, 1953). Many studies have been and still are carried out with motorised ergometers in which the electric motor (generally direct current) drives the chain wheel to rotate in an opposite direction to that of pedalling on a standard bicycle. The subject performs eccentric work, opposing resistance to the movement of the pedals, at a specific rate (defined by the protocol). From the intensity of current absorbed by the motor (previously measured in relation to known resistances) it is possible to calculate the power developed by the subject. Chung et al. (1999) specify that the rate of pedalling is controlled by the motor, via constant control feedback of the current, and the workload is instead regulated by the subject, who voluntarily opposes a varying degree of resistance during each pedal thrust, to achieve the result of displaying on the control screen a power value assigned thereto as target. These ergometers therefore work at a rate (or speed) of constant pedalling, a mode that in the present description will be referred to as "constant speed" mode. Also in the ergometers of Bigland-Ritchie et al. (1973) and of Dufur et al. (2004) regulation of the power developed (or rather absorbed) in eccentric work depends mainly on voluntary regulation by the subject when exercising a varying degree of resistance to the inverted movement of the pedalling. In other ergometers (LaStayo et al., 1999; LaStayo et al., 2000; Meyer et al., 2003) the exact mode of operation is not specified: although there is a system of monitoring and at times also of registration of the current absorbed (which allows - after appropriate calibration - the power absorbed to be monitored), systems are not indicated that are able to regulate the same power automatically in order to render it constant irrespective of the rate of pedalling, that is to say there are no reports of systems able to make the instrument work in "constant power" mode. There is no mention, and therefore it is not known whether it has been applied, of the feature of "constant torque" functioning irrespective of the rate of pedalling. Since in a direct current motor this derives from the supply with a constant current level independent of the number of revs of the motor itself, it is possible that this mode has in fact been applied, although not knowingly or consciously to obtain the benefits derived therefrom. It in fact enables constancy of the resistant torque at the pedals to be guaranteed, a uniformity that is widely independent of the rate of pedalling. In the various studies examined, however, the objective is always that of making the subject exercise at a power as close as possible to the predefined one, which is obviously not feasible by maintaining the torque constant as the rate of pedalling changes (and consequently that of the revs of the motor).
In general therefore eccentric ergometers are designed to actuate the pedals in constant speed mode and the power developed depends on the regulation of the effort in performing movements by the subject carrying out the exercise. Where there is instead the supply of a predetermined fixed current intensity, this takes place as a function of the pedalling rate, in order to obtain a power which is on average close to the target power yet without any feedback device suitable for continually maintaining the same power constant, irrespective of the change in the pedalling rate. Furthermore, to our knowledge, no ergometer has to date been designed and made to be able to function eccentrically with all three of these modes.

Object of the invention

The object of the invention is that of providing an eccentric ergometer which is simple and economical to produce.
More particularly one object of the invention is to allow, should the user be a cyclist, the possibility of using an own bicycle, as is the case for standard stationary pedalling training devices for cyclists (cycle simulation "rollers" and home trainers in general).
Another object of the invention is that of being able to allow eccentric pedalling with three different modes: constant speed (or rate) of pedalling, constant power (irrespective of the rate of pedalling) and constant torque (irrespective of the rate of pedalling). The ergometer according to the invention will also be able to offer the same modes again in conditions of normal (concentric) pedalling.
The ergometer according to the invention has the features described in the attached independent claim 1.
Preferred embodiments of the invention are disclosed by the dependent claims.

Brief description of the drawings

The invention will now be described in greater detail with reference to one of its embodiments purely by way of an example, and for this reason non-limiting example, illustrated in the accompanying drawings, in which:

Fig. 1 is a schematic side elevation view of a cycle ergometer according to the invention;
Fig. 2 is a plan view from above of the cycle ergometer of Fig. 1, where the power unit and control panel are also shown;
Figs. 3 and 4 are graphs showing "constant torque" and "constant speed" operating modes respectively.

Detailed description of the invention

Figures 1 and 2 show schematically a racing bicycle 10 whereto an ergometer is associated according to the invention and denoted overall by reference numeral 1. This consists of a 1.6 Nm direct current motor 2 of the brushless type, supplied with 380 V three-phase current, which actuates a flywheel 4 of approximately 10 kg and 0.5 m in diameter after interposing a reduction gear 3 with ratio 1:5. The flywheel 4 is in turn integral with a cogged pinion 5 (30 teeth) positioned on its same axis and which, via a cogged belt 6, transmits movement to a pulley 7 (72 teeth). The latter is integral with a crown wheel 8 (the same as that normally mounted on racing bicycles) and positioned on the same axis: the width and height of the positioning in relation to the plane of the floor are such as to be able to enter the housing normally intended for the rear wheel of the bicycle, thus allowing blocking of the same bike (with hooking pin 9, the same as that used normally on bicycles) and the transmission of movement to the chain wheel 11 via the chain 12 of the same bicycle. 13 in the drawings denotes a support of the rear hub of the bicycle 10.
Outside of the actual ergometer a control panel 20 is provided, connected to a power unit 21 (Fig. 2) and equipped with a touch screen 22 which allows setting of the required actuation mode (constant rate, constant power or constant torque) and the machine settings (gear ratios of the bicycle and of the ergometer, data obtained from the calibration procedures for the correct calculation of the powers as a function of the rate of pedalling and of the current absorbed, etc.).
The machine is also equipped with safety devices, not shown.

Main modes of operation

1) Constant speed. For operation in the "constant speed" mode - the most classic in eccentric ergometers - it is necessary to set the rate of pedalling at which exercise is to be performed and the duration of the same exercise. By pressing the start key 23 on the control panel, the ergometer sets the rate required, independently of the resistance force exerted by the subject: the power developed by the subject depends in this case on the force that he or she exerts on the pedals at each pedal thrust. The power absorbed by the ergometer (calculated in real time on the basis of the rate and the current absorbed, and constantly shown on the screen) depends on this auto-regulation of force during movement. The control panel allows the succession of different stages which differ one from the other by rate of pedalling to be preset. The setting of stages with different workloads is also possible in the other modes.
2) Constant power. On choosing this mode it is necessary to set on the touch screen 22 the power at which work is to be performed and the maximum exercise rate. By pressing the start key 23, the power control feedback system of the ergometer modulates and regulates in real time the supply of current to the motor in such a way that the absorbed power remains at the value set. In practice this causes an increase in the torque at the motor and, consequently, at the pedals, when the subject tends to pedal at a lower rate than that set. The power supply is also regulated in such a way as not to exceed the maximum rate set in the case wherein the resistance applied by the subject becomes minimal. In eccentric ergometers made for test purposes it is possible that the power absorbed has been regulated by means of an adjustment of the supply current as a function of the rate of pedalling, in this way achieving operation that tends to maintain the power around a certain target value yet with adjustments not in real time and therefore without being able to configure the "constant power" mode of the present ergometer, which is instead carried out in real time and enables a much more accurate uniformity of the power itself. The Applicant is not aware of a power management system with feedback in real time such as the one adopted in the present invention ever having been applied to ergometers able to operate in eccentric mode.
3) Constant torque. On choosing this mode it is necessary to set on the touch screen 22 the maximum nominal work power and the corresponding maximum rate of pedalling: this combination of parameters gives rise to a specific value of torque at the motor - and consequently at the pedals - torque which, after starting, is then maintained constant, irrespective of the rate of pedalling (thus determining progressively lower absorbed power as the rate of exercise set by the subject is reduced). Despite the fact that in "constant power" mode a condition of constant torque is brought about between one regulation (manual or electronic in real time) and the next, we have not found that a "constant torque" function has ever been designed as such, in order to have the guarantee of generating torque that is in fact constant irrespective of the rate of pedalling.

As mentioned previously, the possibility of having the three abovementioned modes of eccentric work (and possibly the same modes during concentric work) represents an innovative feature in the design of the present ergometer.

Advantages arising from the present ergometer

Mention has already been made in the introduction of the possible benefits of pedalling exercise in eccentric mode. As described above, eccentric ergometers usually work at constant speed, subjecting regulation of the load to proprioceptive sensitivity, nociceptive sensitivity and the other factors that determine the perception of effort by the subject performing the effort. This means that, above all in the initial phases (first sessions) of eccentric pedalling exercise, regulation of the effort by the subject is difficult, above all between one pedalling thrust and another. Since eccentric pedalling exercise causes muscle pain in the days following the first work sessions, gradual progression in approaching the workloads set as targets is appropriate (Meyer et al., 2003).
In those over fifty years of age who perform eccentric pedalling exercise in "constant speed" mode two or three times a week, Portusi et al. (2006) have shown how the "ability index" (defined by these Authors as the ratio between the standard deviation of the peak force during each pedal thrust and the average force developed in all pedal thrusts, expressed as a percentage) improves as the sessions proceed, allowing subjects to achieve a fairly constant motor performance (reduced difference in peak force between one pedal thrust and the other) after only 5-6 weeks. It is reasonable to assume that a reduced "ability index" and in general a poor coordination of movement, jeopardising the good coordination of the pattern of muscular activation, may cause higher injury potential of the exercise on the locomotor system (not only muscular, but also osteoarticular), making the gradual approach to this type of exercise even less controllable and modulatable.
The "constant torque" exercise mode instead allows action to be taken so that the motor exerts a constant torque irrespective of the number of revs and therefore irrespective of the rate of pedalling. As a result, for the whole range of rate values below those set as reference during setting of the exercise modes, the torque remains unchanged (even for very low rates). In this case, if the resistance force that the subject exerts tends to exceed the preset value, instead of having an increase in the pressure on the pedals (as occurs in the "constant speed" mode), there is a deceleration in the rate. On asking the subject to pedal at a preset rate (which this subject can check on the screen), he or she then has immediate feedback in relation to the mechanical effect of his or her motor impulses. This feedback system appears to be able to allow better coordination of the thrusts, as fully demonstrated by the graphs in Figures 3 and 4. The same thing does not occur in the "constant speed" mode (Portusi et al., 2006) even if the subject has the power datum as reference feedback for the regulation of his or her thrusts; the control of the movement is in fact less effective and the thrusts less harmonious.
The advantage of the "constant torque" mode is therefore translated into a more immediate application of forces according to a sinusoidal pattern, similar to that which can be found in concentric pedalling. It also allows easier reflected limitation of the peak forces: this specific work mode allows the subject to be exercised over a vast range of rates, without the loads on the locomotor system modifying considerably. This offers clear advantages also in the area of rehabilitation (e.g. after effects of injuries to a lower limb), where the osteoarticular loads must be kept well under control.
As regards the advantages of the "constant power" mode, they are easy to intuit: there is the possibility of having the subject exercise at a known power, irrespective of the rate of pedalling (in the case where the subject is to be allowed a varyingly wide margin of rate of exercise, or it is intended that the exercise be performed over a wide range of rates). The maintaining of the power target required does not therefore lie in this case in the ability of the subject to regulate his or her effort (as in the "constant speed" mode) or to maintain with precision a certain rate (as in the "constant torque" mode) but is automatic under the one condition that the subject pedals within the maximum rate range fixed during the phase of setting of the exercise.
The aforementioned possibility of having these three modes of eccentric pedalling in a single machine is a further exclusive advantage, as it is even more advantageous to be able to have the same functions during concentric pedalling. The cyclist also has the possibility of using his or her own bicycle, thus avoiding hazardous changes to his or her consolidated yet delicate pedalling position.
A further special feature of this eccentric ergometer is the interposition of an effective flywheel 4 between the chain wheel 11 and the drive motor 2 which, although slightly diminishing the effects in the "constant torque" mode, allows the sinusoidal pattern in the application of the forces that characterise concentric pedalling to be maintained better also during eccentric pedalling. If this inertial mass were not interposed, in fact, the adjustment in real time of the current values - particularly in "constant power" mode - would make the passage from the upper and low dead centres of the pedalling (as moreover takes place in conditions of concentric pedalling on ergometers with reduced inertial mass) less fluid.

BIBLIOGRAPHY

Asmussen, E. Positive and negative work, Acta Physiol Scand, 28:364, 1953
Bigland-Ritchie, B. et al. A variable-speed motorized bicycle ergometer for positive and negative work exercise. J Appl Physiol 35:739-740, 1973
Chung, F. et al. Cardiopulmonary responses of middle-aged men without cardiopulmonary disease to steady-rate positive and negative work performed on a cycle ergometer. Phys Ther, 79: 476-487, 1999
Dufour, S.P. et al. Eccentric cycle exercise: training application of specific circulatory adjustments. Med Sci Sports Exerc 36: 1900-1906, 2004
Gregor, R.J. et al. Achilles tendon forces during cycling. Int J Sports Med, Suppl 1:9-14, 1987
LaStayo, P.C. et al. Chronic eccentric exercise: improvements in muscle strength can occur with little demand for oxygen. Am J Physiol Regul Integr Comp Physiol 276: R611-R615, 1999
LaStayo, P.C. et al. Eccentric ergometry: increases in locomotor muscle size and strength at low training intensities. Am J Physiol Regul Integr Comp Physiol 278: R1282-RI288, 2000
Meyer, K. et al. Eccentric exercise in coronary subjects: central hemodynamic and metabolic responses. Med Sci Sports Exerc 35: 1076-1082, 2003
Portusi, J. et al. Description of motor learning process of elderly subjects in eccentric ergometer training. ECSS Congress - Lousanne, 2006

Claims

Cycle ergometer comprising an actual ergometer (1) and a bicycle (10), characterised in that said ergometer (1) transmits movement via a cogged belt (6) to a crown wheel (8) mounted in line with the rear hub of the bicycle, so that the transmission of movement to the chain wheel (11) takes place via the chain (12) of the same bicycle, which is wound on said crown wheel (12).
Cycle ergometer according to claim 1, characterised in that said bicycle (10) is a racing bicycle without the rear wheel and mounted with the rear hub on a support (13).
Cycle ergometer according to claim 1 or 2, wherein said ergometer (1) comprises a direct current motor (2) which actuates, after interposition of a reduction gear (3), a flywheel (4) integral with a cogged pinion (5) positioned on its same axis, engaging said cogged belt (6).
Cycle ergometer according to claim 3, wherein said motor (2) is of the brushless type.
Cycle ergometer according to any one of the previous claims, characterised in that said cogged belt (6) actuates a cogged pulley (7) whereto said crown wheel is integral and coaxial (8).
Cycle ergometer according to any one of the previous claims, also comprising a control panel (20) connected to a power unit (21), said control panel (20) being provided with a touch screen (22) whereby it is possible to set any one of the following operating modes: constant rate, constant power, constant torque.
Cycle ergometer according to claim 6, wherein via said touch screen (22) the machine settings are also possible, such as: gear ratios of the bicycle (10) and of the ergometer (1), data obtained from the procedures of calibration for the correct calculation of the powers as a function of the rate of pedalling and of the current absorbed, etc.