Gait and posture are complex tasks that place considerable demands on both the central and peripheral nervous systems. Research has shown that multiple sensory modalities are involved in the organization and control of human erect posture. The systems involved in the maintenance of balance include the vestibular, visual, musculosensory and plantar cutaneous receptors. Input from each of these sensory systems is cumulative, allowing the central nervous system to activate corresponding stretch reflexes and motor responses. If there is a loss of one of these sensory input systems, as in the case in diabetic peripheral neuropathy, the body compensates by placing a greater demand on the remaining systems. However, if compensations are not rapid enough, the result is a fall with possible injury.
Falls are recognized as an important cause of morbidity and mortality in the elderly, costing the healthcare system millions of dollars each year. Almost one third of those over age 65 and not in a nursing home fall each year. Much work has been done to understand how the body maintains balance, why elderly are at a greater risk of falling and how interventions can be used to reduce fall risk. An important risk factor that has been identified as increasingly more prevalent is diabetic peripheral neuropathy.
Diabetic Peripheral Neuropathy
Diabetic peripheral neuropathy causes loss of distal strength and sensation and is therefore intuitively a risk factor for falls. Clinically apparent peripheral nerve damage may occur in up to 25 percent of patients with diabetes mellitus for greater than 10 years and in up to 50 percent after 20 years. Since all sensory components of the nerve are usually affected, diabetic neuropathy may potentially disrupt both the afferent and efferent pathways in the leg and foot. Such disruption in sensory pathways could increase the likelihood of falls during standing and walking, particularly if there are other sensory impairments such as retinopathy or muscle weakness. The associated postural instability is most apparent during unipedal stance, a critical component in gait and many activities of daily living (ADLs) such as changing clothes and climbing stairs.
Research has shown that diabetics with peripheral neuropathy are at increased risk of falling or stumbling in a one year period versus diabetics without peripheral neuropathy. One retrospective study by Cavanagh et al found that diabetic neuropathic subjects were 15 times more likely to report injury and felt significantly less safe during standing and walking than non-neuropathic subjects. Similarly, another study by Richardson et al found diabetics with EMG-confirmed peripheral neuropathy were 23 times more likely to report instability resulting in a fall or injury versus non-diabetics.
These research statistics emphasize how important it is to create an intervention to improve the stability and balance of diabetics with peripheral neuropathy. When considering an intervention, it is important to look at other conditions that similarly impact balance and gait. Much research has been done to determine the fall risk associated with aging adults as well as chronic stroke patients. Both study groups report a similar fall risk to that of diabetics with peripheral neuropathy and are therefore good comparisons for intervention protocol.
Past research has been done to evaluate the effectiveness of balance training for both elderly and chronic stroke patients. One study by Steadman et al found that just six weeks of balance training for patients aged 60 and older resulted in significant improvements in balance and mobility. A similar study by Waddington et al found that five weeks of wobble board training not only improved balance but also improved ankle movement discrimination capability in elderly individuals with a history of falls. Similarly, in chronic stroke patients with reported muscle weakness and sensorimotor dysfunction, a study by Marigold et al showed 10 weeks of agility training lead to faster postural reflexes, improved balance and fewer falls.
Reducing Falls Among Diabetics
To date, no research has been done showing the effectiveness of either balance training or strength training for diabetics with peripheral neuropathy. With ever rising number of type 2 diabetics in the United States, the need for an intervention program is increasingly more important. Since previous research has shown balance training to be an effective means of preventing falls in the elderly and chronic stroke patients, one can predict that a similar intervention program could be just as effective at preventing falls in diabetic peripheral neuropathy.
When designing an intervention program, one must look at the research to determine the exact mechanism of balance and to determine the role the lower extremity has in triggering balance changes. Research has been done suggesting the impact diabetic peripheral neuropathy has on foot and ankle proprioception and is therefore responsible for the instability often seen associated with peripheral neuropathy. This theory is referred to as the “inverted pendulum” theory.
It should also be noted that researchers challenge this theory as conflicting data suggests that, in fact, peripheral neuropathy’s impact on ankle proprioception has little impact on balance corrections, playing only a small role in balance regulation. This theory is referred to as the “proximal trigger” theory. The proximal trigger theory instead focuses on balance regulation and initiation from the hip, specifically the gluteus medius and erector spinae muscles.
So which theory is correct? How can lower extremity proprioception not play a role in balance control if patients with peripheral neuropathy report instability and increased falls? Or more importantly, why do people fall?
There is little doubt that lower leg proprioception contributes to the control of normal upright stance. Clinical observations support this notion, as balance is clearly impaired in patients with absent Achilles tendon reflexes and in patients with peripheral neuropathy. However, it is difficult to ascertain if the associated loss of balance noted in diabetic peripheral neuropathy is due to impaired proprioception or loss of muscular strength and weakened ankle stability.
Research by Bloem et al indicates that lower leg proprioception does not trigger most balance correcting responses. Instead, these balance correcting responses are most likely initiated more proximally in the hip and trunk and later modulated by lower leg proprioceptive inputs. Several studies have supported this theory by showing that balance correcting responses are still elicited in patients whose ankle rotation has been “nulled” or in subjects with sensory polyneuropathy restricted to the lower leg. Similarly, in the study by Bloem et al, it was shown that the onset of muscle activity in the paraspinals and trapezius preceded that of the tibialis anterior or soleus muscles by up to 20ms.
Role of Strength and Flexibility in Reducing Falls
This does not mean that there is no correlation between diabetic peripheral neuropathy, disruption of sensory and muscular pathways and increased falls. Researchers suggest that the association between diabetic peripheral neuropathy and increased falls could actually be related to muscle strength and corresponding ankle joint stability. Since most diabetic peripheral neuropathy patients experience both a sensory and neuromuscular interruption, it could be possible that muscle weakness is to blame for the increased falls. Similarly, in aging, non-neuropathic adults, instability and increased falls are also reported, possibly secondary to age related muscle atrophy.
Since a gradual loss in muscle mass is a normal sign of aging, the important role of muscle strength in maintaining balance could be possible. The gradual declines in muscle mass and strength are often overlooked by aging adults, that is until eventually weakness results in difficulty performing a task. Muscle mass declines by 0.5 to 1.0 percent annually in both men and women over 60 years old. Leg strength in older women is 23 percent lower than in older men, even after correcting for body mass. This leg weakness is associated with impairment of gait function and is characterized by decreased cadence and shorter stride length, often seen in older women.
It has been shown that lower extremity strength, specifically ankle joint strength, is a fundamental component of the sensorimotor system that supports mobility and stability during gait. A study by Wolfson et al found ankle strength of fallers to be much weaker than control non fallers. By studying falls in nursing home patients versus young, non falling controls, Wolfson et al was able to confirm that the fallers had a delayed muscle response and weaker stretch reflex. Subjects were forced to offset a sudden backwards displacement of body mass in order to remain upright. The young, non falling controls were able to easily accommodate the backwards displacing forces by using muscle synergies to realign the body mass. In contrast, the fallers exhibited poor muscle synergies, were unable to realign body mass and resulted in a fall.
In contrast to these results, researchers have found that patients with peripheral neuropathy but normal muscle strength still report instability and falls. Does this support the previous theory that lower leg proprioception play a greater role in balance control? The verdict is still out.
Designing a Fall Reduction Program
While there is so much more to be studied to determine the exact mechanism and impact of peripheral neuropathy and falls, we can still help our clients reduce falls. It is important to initiate an exercise program for all aging patients as well as those with peripheral neuropathy. It is best to include balance and strength training as well as flexibility training in a client's exercise program. The goals desired from a fall reduction exercise program include the following:
- Re-train the body to utilize the trunk/hip for stability
- Learn to recruit the visual and vestibual systems for enhanced balance control
- Ennhance the strength and stability of the lower leg and ankle joint
When designing the balance training aspect of a fall reduction program for a diabetic, it is important to start all balancing exercises statically on the floor and progressing from there. The safest progressions should start with both feet firmly planted on the ground with eyes open. From here, one can challenge balance by first closing the eyes. By eliminating the visual feedback component, there is a greater recruitment of vestibular and proprioceptive feedback. Remember that diabetics with peripheral neuropathy often cannot feel their feet and will present with increased instability, so be next to your client at all times and progress slowly.
Exercises that can be performed include:
- Basic static stance - two feet on floor
- Tandem stance - two feet on floor
- Unipedal stance - one foot on floor
These are a sample of a safe static progression. Perform each for 30 seconds, first with the eyes open and then closed. Focus on distributing weight equal on both feet, pulling in lower abs with head in line with the spine.
Once stability has been demonstrated on the floor with both eyes open and closed, then it is safe to move these static exercises to foam and air pads and eventually tiltboards. Once static stabilization is established, it is safe to move to dynamic balance by incorporating backward and tandem walking, first on the floor then eventually on a foam beam.
To increase the difficulty of static balance exercises, either on the floor or on balance equipment, you can start incorporating strength training exercises with either dumbbells or a medicine ball. The client can perform lateral shoulder raises while standing on one leg or play a game of catch with a medicine ball while on a tiltboard. The key here is to remember to keep the core engaged while moving to maintain balance.
Strength training is an important component of any aging diabetic’s exercise program regardless of fall risk. Gradual declines in muscle mass and strength are common in the aging population, putting them at greater risk of falling. When designing the strength training component of a fall reduction program, focus should be on the ankle, hip and core muscles, all of which are essential at maintaining balance and posture.
Below are some sample exercises designed to progressively and safely strength stabilizers in the aging diabetic client.
- Resistaband Foot Eversion (15 repetitions)
- Resistaband Foot Inversion (15 repetitions)
- Resista-band Foot Dorsiflextion (15 repetitions)
- Standing Calf Raises (15 repetitions)
- On Back, Engaging Transverse Abdominals (30 repetitions)
- Forearm Plank on Knees/Toes (30 seconds to 1 minute)
- Side Plank on Elbow and Knees or Legs Straight (30 seconds to 1 minute)
- Side Plank on Knees with Leg Abduction (15 repetitions)
- Standing Leg Abduction (15 repetitions)
- Superman on Floor or Bosu (5 repetitions, hold each rep 10 seconds)
- Bridge on Floor or Bosu (5 repetitions, hold each rep 10 seconds)
The final component to any fall reduction program is increasing joint range of motion. As we age, the muscles and ligaments around joints lose their elasticity due a gradual dehydration and increased glycation crosslinks. This gradual loss in elasticity is associated with decreased range of motion, causing shorter stride length, difficulty bending down and a loss of balance.
When beginning a stretching program (especially for the aging population), some key pointers to remember include:
- Start slowly. It will become easier to stretch with practice as the crosslinks are slowly re-aligned.
- Don't force it. Overstretching can cause pain and injury. Your clients might feel slight tension as they stretch/or you stretch them. If it is painful, back off or stop the stretch.
- Breathe deeply. Don't hold your breath. Breathing slowly and deeply will help you relax and make stretching easier. Encourage your clients to exhale as they go deeper into the stretch.
- Warm up. If you stretch with your clients before exercising, make sure to have them warm up for at least five minutes first, with light movement such as walking or marching in place. Avoid stretching a cold muscle, as there is an increased risk of pulling it.
- Stretch all major muscle groups, holding each stretch for at least 30 seconds. Fitness professionals recommend focusing on calf muscles, front and back thigh muscles (quadriceps and hamstrings), hip flexors, chest (pectoral) muscles and upper back muscles. You also can stretch your client’s neck, shoulders, wrists and ankles.
- Stretch three times a week, if possible, and on most days that you exercise. Listen to your body and do what you can. Everyone has a different level of flexibility.
In conclusion, remember that correct technique is essential when performing all balance and strength exercises described in this article. If at any time a client cannot perform an activity using proper technique, you must immediately reduce the level of difficulty until you reach a level in which proper form can be maintained at all times. Try to include all balance training exercises at the beginning of your client’s workout before fatigue has set in. As fatigue increases, so does the risk of injury, especially with increasing intensity.
Although there are risks of injury in all types of exercises, properly executed balance and strength training can improve a client’s balance and postural stability, reducing the risk of future injuries.
Finally, with any diabetic fall reduction program, always remember the desired goals of your training: (1) re-train the body to utilize the trunk/hip for stability by strengthening hip and core muscles; (2) learn to recruit the visual and vestibual systems for enhanced balance control; and (3) enhance the strength and stability of the lower leg and ankle joint.
- Allum, J.H. A Postural Model of Balance-Correcting Movement Strategies. Journal of Vestibular Research. 2:323-347, 1992.
- Aniss, A.M., Diener, H.C., Hore, J., Gandevia, S.C., Burke, D. Behavior of Human Muscle Receptors When Reliant on Proprioceptive Feedback During Standing. Journal of Neurophysiology. 64: 661-670, 1990.
- Bernier, J., Perrin, D. Effect of Coordination Training on Proprioception of the Functionally Unstable Ankle. JOSPT. 27: 264-274, 1998.
- Bloem, B.R. Is Lower Leg Proprioception Essential for Triggering Human Automatic Postural Response? Exp Brain Research. 130: 375-391, 2000.
- Bloem, B.R. Triggering of Balance Corrections and Compensatory Strategies in a Patient with Total Leg Proprioceptive Loss. Exp Brain Research. 142: 91-107, 2002.
- Cavanagh, P.R., Ulbrecht, J.S., Maser, R.E., Orchard, T.J. Problems with Gait and Posture in Neuropathic Patients with Insulin-Dependent Diabetes Mellitus. Diabetic Medicine. 9: 469-474, 1992.
- Kavounoudias, A., Roll, R., Roll, J.P. The Plantar Sole is a “Dynamometric Map” for Human Balance Control. NeuroReport. 9: 3247-3252, 1998.
- Kavounoudias, A., Roll, R., Roll, J.P. Foot Sole and Ankle Muscle Inputs Contribute Jointly to Human Erect Posture Regulation. Journal of Physiology. 532: 869-878, 2001.
- Lin, S., Woollacott, M.H. Postural Muscle Responses Following Changing Balance Threats in Young, Stable Older, and Unstable Older Adults. Journal of Motor Behavior. 34: 37-44, 2002.
- Marigold, D.S., Eng, J.J., Dawson, A.S., Inglis, J.T., Harris, J.E. Exercise Leads to Faster Postural Reflexes, Improved Balance and Mobility, and Fewer Falls in Older Persons with Chronic Stroke. Journal of American Geriatrics Society. 53: 416-423, 2005.
- Richardson, J.K., Ching, C., Hurvitz, E.A. The Relationship Between Electromyographically Documented Peripheral Neuropathy and Falls. Journal of American Geriatric Society. 40: 1008-1012, 1992.
- Richardson, J.K., Hurvitz, E.A. Peripheral Neuropathy: A True Risk Factor for Falls. Journal of Gerontology. 50: M211-M215, 1995.
- Richardson, J.K., Ashton-Miller, J.A., Lee, S.G., Jacobs, K. Moderate Peripheral Neuropathy Impairs Weight Transfer and Unipedal Balance in Elderly. Arch Phys Med Rehab. 77: 1152-1156, 1996.
- Runge, M., Rehfeld, G., Resnicek, E. Balance Training and Exercise in Geriatric Patients. Journal of Musculoskel Neuron Interact. 1: 61-65, 2000.
- Steadman, J., Donaldson, N., Kalra, L. A Randomized Controlled Trial of an Enhanced Balance Training Program to Improve Mobility and Reduce Falls in Elderly Patients. Journal of American Geriatric Society. 51: 847-852, 2003.
- Waddington, G.S., Adams, R.D. The Effect of a 5-Week Wobble-Board Exercise Intervention on Ability to Discriminate Different Degrees of Ankle Inversion, Barefoot and Wearing Shoes: A Study in Healthy Elderly. Journal of American Geriatric Society. 52: 573-576, 2004.
- Wolfson, L., Judge, J., Whipple, R., King,M. Strength is a Major Factor in Balance, Gait, and the Occurrence of Falls. Journals of Gerontology. 50A: 64-67, 1995.