Abstract:
Devices and methods for preventing ankle sprain injuries. To protect the ankle joint from acute ankle supination or inversion sprain injuries, the device comprises a sensing part configured to sense data of an ankle motion; an analyzing part configured to analyze the data to judge whether the motion is a sprain motion; and a stimulating part configured to stimulate one or more lower limb muscles against the motion in light of a result of the analyzing. The method also involves sensing data of an ankle motion; analyzing the data to judge whether the motion is a sprain motion; and stimulating one or more lower limb muscles against the motion if the motion is a sprain motion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 12/539,265, filed on Aug. 11, 2009, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/088,949, filed on Aug. 14, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a device and method for prevention of ankle sprain injuries. The device comprises a sensing part configured to sense data of an ankle motion; an analyzing part configured to analyze the data to judge whether the motion is a sprain motion; and a stimulating part configured to stimulate one or more lower limb muscles against the motion in view of the result of the analyzing component. 
         [0004]    2. Description of the Related Art 
         [0005]    Injuries to muscles, ligaments and bones in lower limbs, such as the lateral ankle ligaments, are very common in sports, which may cause pain and immobility of the legs or ankle joints. For example, injuries to ankle ligaments in the long term may lead to the development of ankle instability, which does not yet have an adequate treatment and rehabilitation protocol. 
         [0006]    Most ankle sprain injuries are caused by a supination or inversion mechanism. It is known that the peroneal muscles are at the lateral aspect of the lower leg, which function to pronate or evert the ankle joint. Therefore, the peroneal muscles serve as the intrinsic defensive mechanism against ankle sprain injuries to resist excessive ankle supination or inversion. However, one of the etiologies of ankle sprain injuries is the slow reaction time of the peroneal muscles. Thus, in most of the injuries, the peroneal muscles are unable to catch up and react to provide the intrinsic protection. 
         [0007]    Currently, myoelectric stimulation has been employed in various medical devices, such as “Functional Electric Stimulus” (FES), to initiate passive exercise to injured muscles for rehabilitation training. Moreover, similar technologies are employed in passive massage devices. In addition, similar techniques have been employed to assist walking in hemiplegic patients who cannot deliver neuromuscular activation to the leg muscle to walk. In all of these devices, electrical signals are delivered to the selected muscle group through pairs of electrodes, which replace the human intrinsic neuromuscular electrical stimulation. The electrical signals can trigger some biochemical changes in muscle cells, leading to contraction of the muscle and thus joint flexion or extension. However, these devices cannot provide quick reaction to prevent acute ankle sprain injuries. 
       SUMMARY OF THE INVENTION 
       [0008]    To prevent an ankle sprain injury, an artificial trigger can be delivered to initiate a peroneal muscle function before the normal muscle reaction. 
         [0009]    According to one aspect of the present invention, a device for preventing an ankle sprain injury is provided, which comprises a sensing part configured to sense data of an ankle motion; an analyzing part configured to analyze the data to judge whether the motion is a sprain motion; and a stimulating part configured to stimulate one or more lower limb muscles against the motion in light of a result of the analyzing. 
         [0010]    According to another aspect of the present invention, a method for preventing an ankle sprain injury is provided, which comprises sensing data of an ankle motion; analyzing the data to judge whether the motion is a sprain motion; and stimulating one or more lower limb muscles against the motion if the motion is a sprain motion. 
         [0011]    According to another aspect of the present invention, a shoe comprising the device described herein is provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a schematic block diagram of the device for preventing an ankle sprain injury according to an embodiment of the present invention; 
           [0013]      FIG. 2  shows a schematic view of a foot with the device according to an embodiment of the present invention; 
           [0014]      FIG. 3  shows a graph of an exemplary electrical pulse generated by the controlling circuit according to an embodiment of the present invention; and 
           [0015]      FIG. 4  shows a schematic view of a user&#39;s feet standing on the mechanical supination sprain simulator according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Hereinafter, a detailed description of embodiments of the present invention will be given with reference to the appended drawings. 
         [0017]    Referring to  FIG. 1 , in one embodiment, a device  100  may include a sensing part  110 , an analyzing part  120  and a stimulating part  130 . 
         [0018]    The sensing part  110  is configured to sense the motions of a user&#39;s foot. To sense the motions of the foot, the sensing part  110  can be attached to an external or internal surface of a heel cup of a shoe, as shown in  FIG. 2 . Alternatively, the sensing part  110  also can be attached to a skin surface of a foot. In operation, the sensing part  110  senses and transmits the data of motions of the user&#39;s foot in a real-time manner. In an implementation, the sensing part  110  comprises a tri-axial accelerometer and a gyrometer for sensing the motions of the foot segment relative to the shank segment. In this case, the data to be sensed and transmitted is the ankle inversion velocity of the user&#39;s foot in motion. In the disclosure, the ankle inversion velocity means the rate of change of the ankle inversion degree of a foot. That is 
         [0000]    
       
         
           
             
               Ankle 
                
               
                   
               
                
               Inversion 
                
               
                   
               
                
               
                 Velocity 
                  
                 
                   ( 
                   
                     deg 
                     / 
                     sec 
                   
                   ) 
                 
               
             
             = 
             
               
                 Ankle 
                  
                 
                     
                 
                  
                 Inversion 
                  
                 
                     
                 
                  
                 
                   Degree 
                    
                   
                     ( 
                     deg 
                     ) 
                   
                 
               
               
                 Duratin 
                  
                 
                     
                 
                  
                 of 
                  
                 
                     
                 
                  
                 Ankle 
                  
                 
                     
                 
                  
                 
                   Inversion 
                    
                   
                     ( 
                     sec 
                     ) 
                   
                 
               
             
           
         
       
     
         [0019]    In another implementation, the sensing part  110  comprises a pressure sensor to sense the motions of the foot segment. In this case, the data to be sensed and transmitted by the sensing part  110  is the pressure to the user&#39;s foot in motion. 
         [0020]    In other implementations, the sensing part  110  may comprise one or more selected from the group consisting of a tri-axial accelerometer, a gyrometer, a goniometer, a pressure sensor and the like. 
         [0021]    According to one embodiment, the sampling frequency of the sensing part  110  may be adjustable. In another embodiment, the sampling frequency of the sensing part  110  is 50 Hz˜1,000 Hz. For example, the sampling frequency of the sensing part  110  may be 100 Hz or 500 Hz. 
         [0022]    The data for each of the motions sensed by the sensing part  110  are transmitted in real time to the analyzing part  120  through a wire or in a wireless manner. A threshold differentiating sprain motions from normal motions is preset in the analyzing part  120 . Once data received about a motion exceed the threshold, the analyzing part  120  transmits a trigger signal to the stimulating part  130 . Otherwise, no trigger signal will be sent out of the analyzing part  120  if the received data do not exceed the threshold, and the analyzing part  120  will process subsequent data. 
         [0023]    In one embodiment, the threshold preset in the analyzing part  120  is adjustable for users with different weights or for different uses such as in walking, sporting, climbing, and so on. 
         [0024]    The stimulating part  130  is provided for stimulating lower limb muscles to prevent ankle sprain injuries. According to one embodiment, the stimulating part  130  comprises an electrical source  131 , a controlling circuit  132 , and a pair of electrodes  133  and  134 , as shown in  FIG. 1 . The electrical source  131  supplies electric power for the controlling circuit  132  connected with the electrodes  133  and  134 . 
         [0025]    In one embodiment, the sensing part  110 , the analyzing part  120 , the electrical source  131  and the controlling circuit  132  are encapsulated in a housing  200  attached to a heel cup of a shoe  300 , and the electrodes  133  and  134  are attached to the skin surface of the peroneal muscle group so as to stimulate the peroneal muscle group, as shown in  FIG. 2 . It will be understood that the housing  200  also can be attached to any other position of a shoe according to the user&#39;s need in practice, by sewing, bonding or any other known coupling manner. Once the stimulating part  130  receives a trigger signal from the analyzing part  120 , the controlling circuit  132  delivers an electric stimulation signal to the electrodes  133  and  134  so as to generate a pulse current through the peroneal muscle group in a lower limb of the user. In one embodiment, the electric stimulation signal is an electric potential difference in pulse with desired level. 
         [0026]    When an electrical signal passes through the peroneal muscle group, the peroneal muscle group of the user may be stimulated to rapidly pronate or evert the ankle joint to prevent the ankle from an acute ankle sprain injury. In particular, when a pulse current from the controlling circuit  132  is delivered through the electrodes  133  and  134  to the peroneal muscle group, the peroneal muscle group may contract and initiate ankle pronation or eversion to resist the sudden supination or inversion. 
         [0027]    According to one embodiment, the electrical signal from the controlling circuit  132  can be delivered through the muscle group within 20-30 ms after the start of a sprain injury. It is known that the torque latency of the ankle muscles is about 21-25 ms. Therefore, the reaction time to a sprain injury is short enough and it could catch up to initiate peroneal muscle contraction to protect the ankle joint. 
         [0028]    According to one embodiment, the electrical source  131  is a set of batteries. By using the electrical source  131 , the controlling circuit  132  can output a pulse with a peak voltage of about 100-200V. Although the peak voltage is quite high, the current is small enough to ensure the safety for the user. 
         [0029]    In another embodiment, the electrodes  133  and  134  are separated by a distance of 1-3 cm on the skin surface of the peroneal muscle group. Optionally, the electrodes  133  and  134  are disposable/replaceable skin-attached silver chloride discs. Furthermore, the electrodes  133  and  134  can be embedded in any accompanying brace or sock with a storage room at the lateral aspect of the lower leg. There may have accompanying apparel which should not block the direct contact of the electrodes  133  and  134  and the skin surface. For the safety, when none skin impedance is detected by the electrodes  133  and  134 , the device  100  will not be activated. 
         [0030]    Moreover, the controlling circuit  132  can comprise an on-off switch to control the delivery of the electrical signal to the electrode pair. 
         [0031]    The physical variable to be sensed by the sensing part  110  and compared with the threshold may be any of variables characterizing the motions of a foot, such as the inversion angle, tilting angle (an angle of the foot segment relative to the ground), tilting velocity, and the like. In one embodiment, the ankle inversion velocity is the physical variable to be sensed. Then, the threshold differentiating sprain motions from normal motions is selected to be a bit higher than the range of the ankle inversion velocity of normal motions of a foot so as to provide a good protection. The range of the ankle inversion velocity of the normal motions of a foot can be obtained via trials. According to one embodiment, the ankle inversion velocity of any normal motion is between 22.8 to 186.7 degrees per second. Moreover, it is reported in “ Biomechanics of supination ankle sprain: A case report of an accidental injury event in the laboratory ”, Fong D T P, Hong Y, Shima Y, Krosshaug T, Yung P S H, Chan K M,  The American Journal of Sports Medicine,  37(4):822-827 (2009) that the maximum ankle inversion velocity of a human is 632 degrees per second. Therefore, the threshold for the activation of the stimulating part  130  should be somewhere between 186.7 to 632 degrees per second. In one embodiment, the threshold for the activation of the stimulating part  130  is set in the range between 190-600 degrees per second, such as 200 degrees per second. Optionally, the threshold may be adjustable from 190 to 600 degrees per second according to the needs of the user. For example, the threshold can be set higher when the user is having a high intensity exercise such as running, hiking, playing basketball and the like. 
         [0032]    For illustration, individuals with healthy ankles are tested to collect data relating to normal motions of a foot. A gyrometer with a size of 20 mm×18 mm×6 mm used as the sensing part  110  is fixed at the heel of a foot of a user or at the surface of a heel cup of a shoe. The gyrometer is connected to a single printed circuit board (PCB) with a size of 50 mm×25 mm×15 mm to collect the data of motions. The gyrometer monitors the inversion velocity of the foot segment. The sampling frequency of the gyrometer is 500 Hz. The individuals perform five normal motions (i.e. non-sprain motions): walking, running, cutting, jumping-landing and stepping-downstairs. Each motion contributes to 10 trials respectively. These motions are chosen because they are common in human daily activities. The sequences of data collection of different non-sprain motions are random. In walking and running trials, the individuals are requested to walk or run naturally for 5 consecutive strides. The data collection starts from the first stride. In cutting trials, the individuals are requested to perform a single leg cutting by their left or right foot. The individuals run for 5 consecutive strides with full speed before the cut, followed by a 90 degrees cut. In stepping-downstairs trials, data of 3 consecutive strides are collected. In jumping-landing trials, the individuals are requested to perform vertical jumping and landing with both legs to their maximum height. In addition, the individuals are allowed to rest between each trial to ensure that their muscles do not fatigue. Results of the tests are shown in Table 1. It can be seen that the maximum inversion velocity of the motions varies from 22.8 to 186.7 degrees per second. It should be noted that if the conditions of the trials and/or the user are changed, the results of the trials may vary. Therefore, these trials are merely illustrative, and do not limit the embodiments described herein. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 The peak values and the time of peak value of the ankle inversion 
               
               
                 angle and the ankle inversion velocity during the five motions 
               
             
          
           
               
                   
                 Walk- 
                 Run- 
                 Cut- 
                 Jumping- 
                 Stepping- 
               
               
                   
                 ing 
                 ning 
                 ting 
                 landing 
                 downstairs 
               
               
                   
                   
               
             
          
           
               
                 Max ankle 
                 −8.3 
                 −13.3 
                 8.7 
                 −2.5 
                 −36.7 
               
               
                 inversion (deg) 
               
               
                 Time of max ankle 
                 0 
                 −0.01 
                 0.78 
                 −0.23 
                 0.04 
               
               
                 inversion (s) 
               
               
                 Max ankle 
                 −151.2 
                 −186.7 
                 −160.0 
                 −22.8 
                 −38.3 
               
               
                 inversion velocity 
               
               
                 (deg/s) 
               
               
                 Time of max 
                 −0.1 
                 −0.08 
                 0.69 
                 0.22 
                 0.25 
               
               
                 ankle inversion 
               
               
                 velocity (s) 
               
               
                   
               
               
                 * Negative value in maximum ankle inversion and ankle inversion velocity means that the ankle is in an everted position relative to the offset position. 
               
               
                 ** Negative time means that the time is before the moment of foot strike. 
               
             
          
         
       
     
         [0033]    According to one embodiment, the electrodes  133  and  134  are attached to the skin surface of the peroneal muscle of a leg of the user. The electric stimulation signal generated by the controlling circuit  132  is an electrical pulse. An exemplary electrical pulse is illustrated in  FIG. 3 . As shown in  FIG. 3 , the electrical pulse has a plurality of cycles. The on-time (i.e. the width) of one cycle, the number of the cycles and the delay-time from the start of a sprain injury to the start of the electrical pulse are all adjustable. According to one embodiment, a simple mechanical supination sprain simulator (which is described in “ A mechanical supination sprain simulator for studying ankle supination sprain kinematics ” Chan Y Y, Fong D T P, Yung P S H, Fung K Y, Chan K M,  Journal of Biomechanics,  41(11): 2571-2574 (2008)) is used for providing a sudden ankle supination of about 15 or 30 degrees so as to evaluate the effect of different electrical pulses. The two feet of a user stand on two plates  500  in the same horizontal of the mechanical supination sprain simulator, respectively, and then one of the two plates  500  falls to provide a sudden ankle supination of about 15 or 30 degrees, as shown in  FIG. 4 . The results of trials with different combinations of these parameters are presented in Tables 2(a) and  2 ( b ). The values are averages of several trials. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
             
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2(a) 
               
             
             
               
                   
               
               
                 Different setting of myoelectric stimulation and the corresponding 
               
               
                 inversion angle when the platform is dropped to 15 degrees 
               
             
          
           
               
                   
                 Myoelectric stimulation setting 
                 Inversion angle of the 
               
             
          
           
               
                   
                 Number 
                 Delay 
                 On-time 
                 ankle when the platform 
               
               
                   
                 of cycles 
                 time (ms) 
                 (ms) 
                 is dropped to 15° 
               
               
                   
                   
               
             
          
           
               
                 No myoelectric stimulation 
                 −10.1 
               
             
          
           
               
                   
                 10 
                 10 
                 5 
                 −5.5 
               
               
                   
                 10 
                 10 
                 10 
                 −4.3 
               
               
                   
                 10 
                 15 
                 5 
                 −5.4 
               
               
                   
                 10 
                 15 
                 10 
                 −5.1 
               
               
                   
                 10 
                 20 
                 5 
                 −5.7 
               
               
                   
                 10 
                 20 
                 10 
                 −5.5 
               
               
                   
                 15 
                 10 
                 5 
                 −5.9 
               
               
                   
                 15 
                 10 
                 10 
                 −5.3 
               
               
                   
                 15 
                 15 
                 5 
                 −4.2 
               
               
                   
                 15 
                 15 
                 10 
                 −4.5 
               
               
                   
                 15 
                 20 
                 5 
                 −6.3 
               
               
                   
                 15 
                 20 
                 10 
                 −5.7 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
             
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2(b) 
               
             
             
               
                   
               
               
                 Different setting of myoelectric stimulation and the corresponding 
               
               
                 inversion angle when the platform is dropped to 30 degrees 
               
             
          
           
               
                   
                 Myoelectric stimulation setting 
                 Inversion angle of the 
               
             
          
           
               
                   
                 Number 
                 Delay 
                 On-time 
                 ankle when the platform 
               
               
                   
                 of cycles 
                 time (ms) 
                 (ms) 
                 is dropped to 30° 
               
               
                   
                   
               
             
          
           
               
                 No myoelectric stimulation 
                 −7.6 
               
             
          
           
               
                   
                 10 
                 −5.5 
                 5 
                 −5.5 
               
               
                   
                 10 
                 −4.6 
                 10 
                 −4.6 
               
               
                   
                 10 
                 −6.4 
                 5 
                 −6.4 
               
               
                   
                 10 
                 −6.6 
                 5 
                 −6.6 
               
               
                   
                 15 
                 −6.3 
                 10 
                 −6.3 
               
               
                   
                   
               
             
          
         
       
     
         [0034]    It can be seen from the results that the inversion angle of the ankle with myoelectric stimulation is reduced by various degrees. 
         [0035]    A shoe or a brace-like or sock-like ankle protector for preventing the ankle from sprain injuries in sports and outdoor activities is provided, which may comprise the device  100  embedded therein. Those skilled in the art can attach the device  100  to, or embed the device  100  into, a suitable position of the shoe or the protector according to the requirements in practice by sewing, bonding or any other known coupling manner. In one embodiment, an intelligent sprain-free shoe with the device  100  can be beneficial for athletics in sprain prevention. 
         [0036]    Furthermore, the device  100  can reduce the cost of treatment in ankle sprain injury. Users also can gain the benefit from a product equipped with the device  100  for preventing sport-related injuries. 
         [0037]    Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment, implementation or example of the invention are to be understood to be applicable to any other aspect, embodiment, implementation or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
         [0038]    The present invention is not limited to the embodiments described above. Variations and modification made by those skilled in the art according to the disclosure herein should be within the scope of the present invention.