I. Overview
The clinical application of partial weight loss gait training can be traced back to 1958 when Margaret H and Margaret HSR published the monograph “Suspension Therapy in Rehabilitation”. In 1973, Grillner demonstrated that kittens born 1 week after the destruction of the spinal cord at the level of the lower thoracic segment could walk with their hind limbs placed on a treadmill (TM) 2 d later. In the late 1980s, Visintin et al. used body weight support treadmill training (BWSTT) in paraplegics with incomplete spinal cord injury and achieved good results in some wheelchair-dependent patients. Since the 1990s, this device has been used with some success in the walking training of patients with paraplegia, hemiplegia, cerebral palsy and lower limb osteoarthrosis. Since the introduction of partial body weight sup-port treadmill training (PBWSTT) in 1992 for lower extremity rehabilitation of hemiplegic patients, great progress has been made in the research of this therapy at home and abroad. Although treadmill has become popular in China in recent years, its use for gait recovery of hemiplegic patients is still relatively rare, and there are very few reports on it. Therefore, we still need to make further research and discussion on this therapy.
Partial weight reduction gait walking training is one of the rehabilitation therapies that have received attention in recent years. It mainly involves suspending the patient’s body partly in a weight reduction sling to reduce the weight of the lower limbs when walking and improve walking performance. The application of this new treatment technology has attracted the attention of scholars at home and abroad. There are various kinds of suspension weight reduction training machines, the main types are suspension rope lift control, that is, the suspension bar does not move, while the suspension rope can move up and down, and suspension bar lift control, that is, the suspension bar can move up and down, while the suspension rope and fixed belt does not move. The system consists of two parts:that is, weight reduction device and electric activity plate, weight reduction device mainly includes fixed support frame, weight reduction console, electric lifting rope or rod, body fixed belt (i.e. weight reduction sling) several parts. Both of the above models can be used in electric and manual ways, and there are two types of suspension arms: single-arm and double-arm. Both types of weight loss trainers can be equipped with force measurement devices and display the amount of body weight loss in each state. The training can be ground walking or moving plate walking according to the patient’s needs. The force point of the suspension belt is usually in the waist and perineum, not in the armpits or thighs.
Second, the basic theory of partial weight loss gait training
1.Walking center
Walking is a “simple” activity. In general, walking does not require cortical involvement. Some animals can still crawl after the brain is removed, suggesting the existence of a crawling or “walking” center in the spinal cord. In humans, however, walking is closely related to cortical function, and in complex situations and special tasks, the cerebral cortex is directly involved in the control of walking posture, and Fukuyama et al. used PET to find an increase in cortical energy metabolic activity during walking, suggesting cortical involvement in walking activities. In contrast, during brain dysfunction, the role of subcortical and spinal cord centers is released or intensified, leading to abnormal compensatory activity. Direct impairment of cortical, brainstem, cerebellar and spinal cord function or conduction pathway disorders can lead to different types of walking dysfunction, and the intrinsic regulatory mechanisms are so complex that academics have so far been unable to identify the site and function of the human walking center.
2. Central Pattern Generator (CPG) theory
Grillner and Debuc et al. proposed that the CPG exists in the mammalian spinal cord to generate nerve impulses such as gastrointestinal motility and alternating flexors and extensors in walking; the CPG exists on the ventral and central sides of the spinal cord, with nerve signals communicating between them, most frequently in the cervical and lumbar regions of the spinal cord. Shepherd transected the thoracic spinal cord of the cat and then started “walking” by suspending the cat on a movable plate, recording the movements of the hind limbs and EMG activity. The cat was found to be able to perform alternate limb movements on the plate, and regular electromyographic activity was recorded. It was found that the cat could perform alternate limb movements on the activity plate, and regular EMG activity was recorded. Barbeau et al. found that intrathecal injection of clonidine activated active movements in cats 8 days after spinal cord transection, suggesting that CPG activity is related to the activity of spinal cord neuromediators. The CPG theory of spontaneous alternating flexor and extensor activity during walking is that flexor excitatory impulses inhibit extensor activity via interneurons, and neural excitation of the extensor muscle is released after completion of flexor excitation, causing extensor activity, thus producing spontaneous alternating flexor-extensor excitation after the initiation of walking action (see Fig.)
3. Neurological plasticity and functional reorganization
The plasticity of the nervous system refers to the mechanism by which the nervous system can learn and train to perform the functions lost due to lesions, including the fading of distal functional inhibition, germination, replacement, and activation of potential synapses. After brain injury, adults have the ability to reorganize structurally or functionally to assume the lost functions, i.e., to complete functional reorganization, and this process must be gradually achieved through directed induction.
4, motor control of the “dynamic system” theory (dynamic system theory)
It is believed that the control of movement arises from purposeful behavior, therefore, the rehabilitation treatment for patients with damaged motor centers should focus on practical tasks, including the main task of the lower limbs, “walking”. Walking training allows the motor centers of the brain to relearn the control of lower extremity movements. Recent studies have confirmed that task-specific exercises help stroke and spinal cord injury patients to achieve optimal motor relearning results. This afferent sensation may expand the cortical and subcortical motor areas, so that the motor center’s control of movement is enhanced.
5. The main factors of walking control
Excitatory release from spinal cord centers leads to limb spasm, stiffness, and tremors, mostly seen in stroke, traumatic brain injury, and high spinal cord injury. Blockage of downstream control leads to limb weakness and paralysis, mostly seen in peripheral nerve injuries and anterior horn lesions of the spinal cord. The main factors affecting walking control include.
(1) Stretch stimulation of the hip flexors, which is an important factor in the induction of CPG. Restriction of posterior extension of the cat’s hind limb can significantly limit hind limb electromyographic activity, so patients with hip flexor contracture must be strengthened with distraction training.
(2) Duality of lower limb weight-bearing. On the one hand weight reduction training is to promote walking by reducing the body weight-bearing. On the other hand, it should be noted that weight-bearing itself can promote the activity of the extensor muscle groups of the lower limbs. Lower extremity weight-bearing reduction does not change the temporal phase of EMG, but reduces EMG amplitude. The magnitude of weight reduction should be reduced to the smallest extent that the patient can initiate walking.
(3) Gait: Accelerated gait speed does not significantly alter the oscillatory phase of walking, but significantly shortens the bracing phase.
(4) The cerebral cortex has direct control over walking movements.
(5) Appropriate lower limb weight-bearing is conducive to promoting the role of sensory feedback on the regulation of walking movements.
6.Natural recovery of neurological function
The process of innervation loss in neurological paralysis can be partially or even fully recovered naturally.
Barbeau et al. found that decorticated cats could spontaneously recover the full skills of motor avoidance, foraging and performing complex movements. Therefore, it is important to establish control groups in studies of weight loss training to avoid erroneous conclusions.
III. Indications for partial weight reduction gait training
1, neurological diseases: cerebrovascular accident, traumatic brain injury, brain tumor, limb paralysis caused by brain inflammation, cerebral palsy, Parkinson’s syndrome, paraplegia after spinal cord injury due to various reasons, lower limb muscle weakness caused by peripheral nerve injury.
2, bone and joint diseases and sports trauma recovery period: early lower limb weight training after lower limb joint replacement, functional recovery training after surgery for bone and joint lesions, training to relieve pain and promote functional recovery for bone and joint lesions, early recovery training for sports trauma such as tendon and ligament rupture.
3.Lower limb gait training before and after wearing prosthesis and orthosis.
4.It is suitable for early small-volume safety aerobic walking training for elderly, frail and bedridden patients.
5.Adapted to the aerobic walking training for patients with excessive weight and serious degenerative joint disease.
Weight loss walker is mainly used for walking training, but it can also be used for balance training, postural transition training and daily living ability training in occupational therapy for patients.
Fourth, some of the contraindications to weight loss gait training
1.Spinal instability.
2.Lower extremity fracture not fully healed or joint injury in unstable stage.
3.Patients cannot cooperate actively.
4.Excessive muscle spasm is induced during exercise.
5.Postural hypotension.
6.Severe osteoporosis.
Cautiously used in the lower extremity active contraction muscle strength less than 2, no configuration of orthopedic devices to avoid joint injury.
V. Selection and use of training equipment
Weight reduction devices must be safe and reliable, should meet the following requirements, in order to prevent patients from falling, to ensure safety, should be able to withstand 150% – 300% of the patient’s body weight. The patient’s center of gravity should be allowed to move up and down without affecting the patient’s upright posture. In the process of patient’s fall, that is, when the displacement of the center of gravity is greater than 5.5cm, the system should be able to pull it in about 0.2s, when the patient’s center of gravity is displaced by about 11.2cm. It should be easy to put on and take off, reliable, comfortable and so on. The movable plate should have suitable length and width, preferably around 15060cm, with handrails, preferably equipped with a ramp device for patients in wheelchairs to get up and down, and a table with a width of about 25cm on both sides of the conveyor belt for the therapist to assist the patient to walk. The running speed of the movable plate should be finely adjustable (accurate to 0.15km/h), able to run at a very low speed (0.1 – 0.3km/h) without pausing or shaking, and able to stop the transmission quickly and safely in case of emergency.
VI. Partial weight reduction gait training for hemiplegia
1. Staffing for partial weight loss gait training for hemiplegia
At the beginning, two therapists will correct the gait deviation. One therapist is on the affected side to help facilitate the swing of the affected lower limb; to make sure the heel lands first; to prevent knee hyperextension; and to ensure that the standing time of both legs is symmetrical with the step length. The other therapist stands behind the patient with both feet on the edge of the activity plate: promotes weight transfer to the weight-bearing leg; ensures hip extension, pelvic rotation, and trunk uprightness; and prevents sitting in a sling. As the gait improves, gradually transition to a therapist standing behind the patient or next to the activity plate to give guidance, and finally complete walking on the activity plate independently.
2.Assessment of partial weight loss gait training for hemiplegia
(1) Walking ability
The functional ambulation category scale (FAC) is usually used.
Level 0: Patients cannot walk or walk with the help of 2 people;
Level 1: The patient needs continuous support from one person to lose weight and maintain balance;
Level 2: The patient walks with the continuous or intermittent support of one person;
Level 3: The patient walks without direct physical support from another person and under supervision;
Level 4: The patient is able to walk independently on level ground, but requires assistance in walking up and down stairs, up and down slopes, or on uneven paths;
Level 5: Patients can walk independently.
(2) Walking speed
The walking distance is usually calculated for 5 min or 10 min, and then the average of the 2 measurements is calculated. If the patient cannot walk continuously for 5 min or 10 min, the speed is recorded as 0. Among them, 5 min walking distance is more commonly used and walking speed is calculated in m/s.
(3) Walking distance
The patient walks back and forth for 5 min in a set field, and then calculates the total distance walked. The patient is asked to walk as fast as possible, if he/she cannot walk continuously, he/she can combine standing and walking, if he/she cannot walk 5mim in this way, the result will be recorded as 0. Some rehabilitation therapies set this time as 6-12min.
(4) Gait energy expenditure
One method is to calculate the oxygen consumption of the patient walking in 5min; another method is to calculate the oxygen consumption per unit distance of 5min walking, that is, the former divided by the distance of 5min walking.
(5) Balance function measurement
There are two main methods: Berg balance scale (Berg balance scale, BBS) and Fugl-Meyer balance scale measurement method. The BBS is the most commonly used and was first reported by Katherine Berg in 1989. 14 movements were selected to assess the test subjects, and each movement was divided into 5 levels based on the quality of the test subject’s completion, with a maximum score of 56 and a minimum score of 0. The lower the score, the more serious the balance impairment. Meyer assessment method is also more commonly used, including balance, sensory, ROM, pain, motor function assessment, but there are too many items, time-consuming disadvantages. Nowadays, a balance meter imported from the UK is often used to measure and analyze the balance function of patients before and after training. Other assessment tools include: lower limb electromyographic activity, changes in muscle tone, ability to perform activities of daily living, stride length and gait type. Among the above assessments, the most commonly used ones are FAC, BBS, walking speed, etc.
3.Prescription of partial weight reduction gait training for hemiplegia
The speed of the activity plate should be set according to each patient’s specific situation, i.e., individualized, so that each patient has an appropriate step frequency and stride length. The literature reports starting at 0.09m/s (0.07–0.11m/s) gradually reaching 0.17m/s (0.12–0.23m/s) until the end of training.
(1) the degree of weight loss: as soon as possible to make the lower limbs fully weight-bearing, weight loss is only to create conditions for the transition to normal weight-bearing.
The weight loss should be 20% to 40% of body weight at the beginning (average 30% of body weight), up to 70% of body weight, and gradually decrease the weight loss (increase the weight of both lower limbs) as the gait pattern improves, and finally reach full weight-bearing walking.
(2) Treatment time: according to the principle of gradual progress and gradual extension. At the beginning, 15min/time, after 3-5 days, 30min/time, 5 days/week. The duration of training is mostly 5 weeks – 2 months.
4.The operation procedure of partial weight reduction gait training for hemiplegia
(1) Explain to the patient the purpose and process of suspension weight reduction training and the patient’s cooperation.
(2) Check the mechanical or manual lifting device of suspension weight reduction to make sure it is in normal condition. If using a movable plate, the plate must be at the slowest possible speed (preferably at rest).
(3) Make sure there is no damage to the suspension straps and no looseness or damage to the various connecting parts.
(4) Place the patient in the suspension straps, paying attention to all attachment areas.
(5) Bring the patient under the weight-reducing cantilever and attach the suspension belt.
(6) Pull the patient’s suspension belt through the weight-relief cantilever using electric or manual means.
(7) Determine the degree of weight reduction based on the patient’s ability to step forward, either actively or with assistance.
(8) Have the patient stand on the training field or activity plate and keep the body stable for 2 to 3 min to acclimate the patient to the upright position.
(9) Turn on the activity switch of the plate or from the ground where the patient is standing and step forward by the patient’s active or assisted way.
(10) Gradually accelerate the speed of the activity plate to the fastest pace to which the patient can adapt.
(11) Gradually decelerate after reaching the training time.
(12) Prepare a chair or wheelchair, gradually lower the suspension belt and allow the patient to sit. Remove the suspension straps.
(13) Turn off the machine and let the patient rest for 3–5 min to complete the treatment process.
5. The role of weight reduction training to improve hemiplegic gait
In 1999, Hesse et al. performed gait analysis, dynamic electromyography examination and comprehensive walking ability assessment of 14 hemiplegic patients before and after PBWS plate walking training, suggesting that the effects of PBWS training mainly include.
(1) PBWS suspended the body by a computer-controlled weight-reducing sling, reducing the weight-bearing on the hips and both lower extremities during walking, which might make the distribution of body weight in walking symmetrical and improve the walking stability of patients;
(2)Reduce the contraction load of the lower limb related muscle groups in walking, so that patients with small lower limb muscle strength up to grade 3 can carry out gait training early, which is conducive to the patient’s early bed talk;
(3) The reduction of lower extremity joint load can improve and increase the range of lower extremity joint movements. Hesse reported that patients with hemiplegia and hip arthroplasty had an increased range of hip extension after weight loss plate training and a corresponding increase in stride length, thus increasing walking speed;
(4) The muscle tone of the lower extremity can be regulated in the weight-reduced state to avoid and alleviate the unnecessary synergistic movement of the lower extremity extensors due to early weight-bearing walking and the pathological gait such as foot drop and inversion caused by this abnormal pattern, and to input the walking pattern in line with normal human physiology at an early stage to promote the recovery of normal gait and improve walking ability. Hesse observed the changes of electromyography in the lower limbs of patients with hemiplegia during weight loss plate training and found that the electromyographic changes of the affected side of the vastus medialis, tibialis anterior and sacrospinous muscles were close to those in the normal walking cycle, supporting the above view;
(5) Patients’ safety was improved under the protection of the weight-reducing device, which eliminated the patients’ tension and fear in walking, so that they could better cooperate with the therapist’s treatment, and the therapist could also focus on the correction of abnormal gait of the lower limbs.
6. Partial weight loss gait training compared with traditional walking training methods
The common goals of neural facilitation techniques, which are the traditional training modality for stroke patients, are to improve muscle contraction; increase functional stability; promote relearning of normal movement patterns; promote the ability to respond to external forces in multiple directions; increase motor neuron recruitment; increase gait control; and increase the weight-bearing capacity of the lower limbs.
Svendsen believes that the new treatment goals should be: reasonable muscle activation, harmonious muscle contraction timing, adequate weight-bearing capacity and endurance, and PWS is the most effective gait training technique for stroke.
7. Partial weight loss gait training compared to traditional crutch and parallel bar walking training
Both Hesse et al. and Tyson et al. reported no significant beneficial effects on gait in hemiplegic patients trained with different crutches, walkers or parallel bars. On the contrary, because the training required strong upper limb support for the patient, the upper body posture was often incorrect and a new incorrect gait was developed. With 40% PWS training, the walking training effect is better than parallel bar training, so PWS has the potential to be the most effective walking training tool.
Seven, part of the weight loss gait training considerations
1. The suspension fixation belt should be appropriate and should not induce spasm in patients. Male patients pay special attention to the sling should not compress the testicles. Suspension weight should not fall in the armpit, so as not to cause brachial plexus nerve injury. The sling should not be fixed on the thighs in general, so as not to affect the gait.
2, because the patient has a sensory impairment, when fixing the weight loss belt should pay attention to the elasticity of the appropriate, easy to rub the parts to add padding to protect the skin, to prevent abrasions.
3, fixed weight belt to pay attention to the left and right balance, each weight loss before the weight machine to “zero”.
4, long-ill bedridden patients before starting to receive weight loss training, first upright bed position training to prevent postural hypotension.
5, the degree of weight loss should be appropriate, the general weight loss of no more than 40% of body weight. Excessive weight loss will lead to an increase in body swing and a decrease in proprioceptive feedback afferent to the lower extremities. Insufficient weight loss will lead to difficulty in walking.
6.Suspension devices must be reliable to avoid loosening or slipping of the sling and causing the patient to fall.
7.There must be medical personnel present during the training process for guidance and protection.
8.Avoid the danger of too fast starting speed or too fast acceleration of the active plate.
9, weight loss plate aerobic training patients should pay attention to the training of blood pressure, heart rate changes, with vertigo, heart failure, blood pressure fluctuations should be cautious training.
10, walking patients can be equipped with orthopedic devices for training.