Aquatic Gait Training

Editor’s note: This text-based course is a transcript of the webinar, Aquatic Gait Training, presented by Marty Biondi, PT, CSCS, ATRIC.  Please download course handout and follow along to ensure understanding of material and assist in taking end of course exam.  

Aquatic Gait Training: Comparing Land and Water Gait Sequences

When we think of walking, really, "Nothing epitomizes the level of independence "and our perception of a good quality of life "more than the ability to travel independently "under our own power from one place to another." That's Patla's real definition of the function of walking.  Walking is the most common activity for the majority of the world’s population, and it fulfills a simple need: to get from one place to another. Because walking is such a common task, it appears to be effortless. As physical therapists, we are constantly trying to discern what is occurring in a patient’s gait, particularly when that is their issue. Years of practice enable humans to multitask while walking, to handle obstacles, and to destabilize forces with minimal effort. With age, however, this often changes. The challenge of ambulation occurs at both ends of the lifespan. The young need months to normalize their gait, and later in life, individuals are presented with multiple walking challenges. Humans celebrate this ability in children, but we should nurture gait throughout the lifespan.

Review of Gait Descriptors

Spatial-temporal gait characteristics are the most widely reported measures to identify deficiencies in walking ability on land, as these characteristics are easily measured. The following table (Figure 1) is a depiction of gait descriptor averages for a 7-foot-8-inch male:

Figure 1. Gait descriptor averages for a 7-foot-8-inch male.

The step lengths depicted in Figure 1 would be excessive for someone considerably shorter or older. You can find charts of specific age and gender descriptors, detailing gait speed, step lengths, and step-widths online. Stride-length is the measurement of the heel of the right foot to the successive heel of the right foot. This measurement is considered the hardwired component of our gait and is a number thought to decrease with age.

Gait Speed as the Sixth Vital Sign

Gait speed is considered the sixth vital sign, or more importantly, the functional vital sign. It is thought to be the best measurement of functional criteria for gait, regardless of the quality. Gait speed relates to the amount of time it takes to cover a specific distance and is determined by multiplying time by distance. It is considered a measure of the functional outcomes of the walking process and provides a summary of neurological and mechanical processes involved with gait.

Gait integrates the musculoskeletal, cardiovascular, pulmonary, sensory, neurological, and vestibular systems. It is related to the individual’s ability to integrate the input that the brain receives, and then manage the terrain the individual intends to navigate.  This is a complex process, however, it is something that most individuals do without even thinking about it. This assimilation, this integration of multiple systems, makes gait a great functional measurement. And, because the majority of people walk, it is also an equalizer when evaluating across populations. Finally, gait integrates unrecognizable disturbances in multiple organ systems. Consider the cardiovascular system and the musculoskeletal system: if an individual is deconditioned and has a heart condition, their gait speed will reflect the condition.

Gait speed is associated with survival in older adults, as slow gaits are indicative of increased energy costs and damaged systems. A decreased mobility may prelude a cycle of reduced physical activity, which has dire effects on a person’s health in general. Decreased walking speed with increased double leg stance time increases energy expenditure by requiring increased efforts to advance the trunk and lower extremities. Older individuals spend more time in the double leg stance, and so are getting less benefit from momentum.

In 2009, Stacy Fritz PT, PhD, and Michelle Lusardi PT, PhD, produced a white paper entitled, “Walking Speed: the Sixth Vital Sign.” It was published in the Journal of Geriatric Physical Therapy as strictly a guideline. Then, in 2015, Addie Middleton, PT, DPT, Stacy L. Fritz, PT, PhD, and Michelle Lusardi, PT, PhD, published “Walking Speed: the Functional Vital Sign” in the Journal of Physical Therapy. The 2015 study narrowed down the message of changes in gait speed when there is no other mitigating factor and convincingly argued that gait speed is a summary indicator of multiple physiological system inputs, and reflective of an individual’s overall health. The following are findings from the 2015 study:

• If an individual walks at less than 0.6 meters per second (approximately 1.3 miles per hour), the individual was found to be highly dependent with an increased fall risk. These individuals have functional impairments, and are household walkers; they are not going outside.
• At 0.6 to 1 meter per second (between 1.3 and 2.2 miles per hour), the individual is a limited community ambulator. They might go outside to get the newspaper. Limited community ambulators are also at an increased fall risk, and were found to have a cognitive decline within 5 years of the date they produced these test results.
• Functional community ambulators walk faster than 1 meter per second. These individuals are not fast, but are efficient enough to accomplish their goals.
• The group of individuals from 1.4 meters per second and over (roughly 3.1 miles per hour) are individuals who can cross the street safely, are generally fit, and are able to climb multiple flights of stairs without an issue.

For perspective, individuals in the military walk at 120 beats per minute, which translates to 4 miles per hour. And, individuals typically begin to run at approximately 4.5 miles per hour, though this is not necessarily accurate for very tall individuals.

Gait speed is a summary indicator of an individual’s health, motor control, muscle performance, sensory and perceptual functions, cognitive status, motivation, mental health, and the characteristics of the environment, be it land or water. Clinicians can rely on this information to provide an accurate assessment of function, and can also use the information, especially when changes unexpectedly occur, as a means to indicate underlying medical conditions that have yet to be defined by conventional tests.

As an aside, Medicare now requires physicians seeing older adults to provide an assessment of gait speed in their physical evaluations because it is a mark to evaluate the functional performance of the total individual. It actually might be more beneficial to evaluate as we do in physical therapy, looking also at stops, starts, and turns. For example, the Timed up and Go test (TUG,) which is not a good indicator of gait speed, but concerns functional gait: stopping, starting, and changing position.

Land Characteristics Review

The land characteristics review will help to understand and coordinate what is occurring in the water, by evaluating the gait sequence, the joint involvements, and the muscle activations. This section is meant to be an overview and is by no means comprehensive. This review will set the stage for how we as therapists define deficits, what we plan to address with therapeutic interventions and the reasons for transferring a patient into the pool at a certain point of the rehab process. Without first understanding the specificity of gait sequencing, the joints involved, and muscle activations at specific points in the gait cycle a therapist cannot make an educated decision as to when to put a patient into the water, or when to take a patient out of the water.

Gait Sequence

The stance phase. The stance phase of the gait sequence represents approximately 60 percent of the gait cycle on land and is initiated with weight acceptance to progress over the supporting foot. Think of it as an accommodating foot, and then as that foot lands, it is followed by increased weight bearing through a rigid lever or a very stable surface. This provides a surface tough enough to manage, and also to move the weight of the person above it forward without too much effort. Again, increased double leg stance is indicative of an underlying pathology, and it is witnessed often in older adults. It is critical to know what the tibia is doing throughout the stance phase, as it is responsible for placing the foot in its appropriate position to accept weight, and also to provide stability for the knee.

Double limb support equates to about 20 percent of the stance phase, though less in situations such as race walking and more commonly noted with underlying pathologies. This is important to evaluate, because the pathologies may be completely unrelated to ankle and foot usage during walking. For example, someone with hip pain may spend more time on 2 feet which makes the gait process metabolically more difficult, and possibly creates balance and posture issues.

The swing phase. The swing phase represents about 40 percent of the gait sequence. Toe clearance is the critical issue at initial swing, so gait is not impeded by foot dragging. The swing phase relies mostly on the eccentric work of the hamstrings, less so the hip flexors, to slow down the acceleration of the swinging leg, so that the heel can be placed in a very accurate position and initiate the stance phase. When walking, individuals probably never consider where their heel is going, but even if it is an inch off, it can result in balance discrepancies. It is also critical to consider reaching the heel forward in terminal swing, so that the individual can continue the weight transference using momentum, and can move forward easily. When race-walking, an individual functionally places their foot much further than normal, so that they are stepping wider lengths and moving faster.

Joint Involvements

Motion at the pelvis. In the sagittal plane, the pelvis moves about 2 degrees to 5 degrees per step, and although this motion will increase with increased walking speed, it is an accurate assessment of how it will normally move. When we ascertain discrepancies on one side or the other, there could be an issue.

A race walker moves the pelvis drastically in the sagittal plane. That increased drop allows for a functionally longer leg so that the heel can be placed forward at an increased distance, which translates to increased step length. This drop of the pelvis in the sagittal plane is affected also by muscle imbalances (specifically, weak adductors), because if these are weak, there is an increased drop of the pelvis on the stance side or a lateral flexion of the trunk. This particular situation is important to the vertical displacement of the center of mass.

At mid-stance, the pelvis is a bit anterior, and at push-off to swing, it is a bit posterior. In the frontal plane or right stance, the left iliac crest moves downward due to a drop in the center of mass, while the frontal plane pelvic rotation assists with minimizing energy expenditure.  Excessive motion is seen in older individuals with specific pathologies causing instabilities, and in younger individuals who have what therapists call “a very lazy walk.” This is frequently due to weakened gluteus and/or trunk muscles, and also hip structures. It is as if the pelvis is bounding between the most extreme positions, which makes an individual susceptible to lower back and lateral hip structural discrepancies and pain. In the transverse plane, the pelvic motion increases the step length, depending on the hip position.

Motion at the hip. In the sagittal plane, for normal gait, the hip moves approximately 30 degrees of flexion and about 10 degrees of extension. When hip mobility is deficient on either end, it increases the need for increased pelvic and lumbar spine mobility. Additionally, when either of these structures is not mobile, there are drastic alterations in the forces passing through the joints, frequently resulting in adverse effects such as prolonged walking, and increasing lower back pain.         

In the frontal plane, the individual is abducted in stance phase and adducted in swing phase. In the transverse plane, it is predominantly dependent on the amount of pelvic motion that is available. Particularly in the transverse plane, consider that the femur is fixed and the pelvis must move over it, so again, depending on strength and/or specific muscle imbalances, this could be an issue.

Motion at the knee. Gross deficiencies are most obvious in the motion at the knee. In the sagittal plane, a minimum of 60 degrees of flexion is required, and full extension is required at mid-stance. A lack of flexion affects the swing phase and can result in substitution patterns including hip hiking and contralateral lateral trunk shift, and decreased knee extension that causes the contralateral hip to hyper flex. Individuals with knee osteoarthritis, a very common condition, often have decreased full extension which affects stance and swing phase. An adjustment must be made, as it will affect the entire lower chain and moving up.

In stance phase, knee flexion is important to minimize energy expenditure. At the initial part of stance, the knee is about 10 degrees to 12 degrees flexed. When the individual steps over the non-accommodating foot, it turns into a rigid lever as the individual completely extends the knee. In the frontal plane, therapists should note minimal valgus. Finally, in the transverse plane, because the tibia rotates internally faster than the femur during stance, there is a net minimum internal rotation at the knee.

Motion at the ankle. The sagittal plane requires 10 degrees of dorsiflexion plus 20 degrees of plantar flexion for normal gait sequence. The 10 degrees also maximizes a safety issue: if an individual cannot get to 10 degrees of dorsiflexion, they are at a significantly increased risk of falling. For dynamic balance, it is important to have not only 10 degrees of dorsiflexion, but also 20 degrees of plantar flexion. If an individual lacks plantar flexion, it affects their stance and swing phases. Decreased dorsiflexion affects the stance, and is a risk factor for falls. If the individual doesn’t go into supination, they significantly challenge the plantar flexion portion of their entire gait cycle.

Regarding the frontal plane, early stance requires eversion and pronation for a compliant foot, followed by supination and a rigid foot to propel the body weight over. Pronation is the key for shock absorption and loading. When discussing water gait, it is easy to see why we don't require a pronated foot, as the ground reaction forces in water are significantly diminished due to buoyancy. As far as supination, it creates the rigid lever for the individual to propel over, and this is critical for propulsion. Again, in the water, the individual may not need such a rigid lever, and we don't often times see that there is a problem with supination.

Motion of the trunk. Trunk rotation at the shoulder girdle is about 7 degrees for each forward step. This rotation is an important component of dynamic balance; it allows the individual to maximize the momentum moving forward. The absence of this trunk rotation increases the energy expenditure of walking by at least 10 percent. Thus, for a compromised individual without this motion, walking is drastically harder metabolically. In the pool, therapists can easily facilitate trunk rotation, and can also strengthen the lateral structures of the trunk. The trunk moves into flexion and extension, out of phase with the hip motion; it is this lack of coordination that can exacerbate an individual’s back conditions. The shoulders, on the other hand, rotate opposite to the pelvis and rotate in a transverse plane.

Summary of joint involvements. The above provides a succinct overview of the normal joint motions while walking on land, and enables us to consider how to use the water to facilitate, for example, hip flexion or trunk rotation in order to improve land walking.

Muscle Activations

During land gait, muscles work at approximately 20 percent of their max. However, this percentage will change when increased effort is needed: when accelerating, changing directions, or walking on uneven surfaces. In the lower kinetic chain, the adductors are active for most of the walking cycle; with hip extension, they assist the contralateral hip flexion; with flexion, they help to stabilize the hip and assist with extension. Going up the kinetic chain, the transverse abdominis is active for the majority of the gait cycle, but at a very low grade. Depending on the walking surface, the trunk extensors are also often times active for the majority of the gait cycle.

Hip flexors. In the hip flexors during land gait, there is a concentric pre-swing to initial swing that helps to advance the lower extremity. Thereafter, there is eccentric activation in the terminal stance to control hip extension, so that as the individual toes-off, their leg doesn't get lost behind.

Hip extensors. It is then important for the hip extensors to activate, and slow down the process, so that the individual can place the foot in a very precise position, time and again. The hip extensors are primarily the eccentric controllers of the terminal swing to pre-stance; they decelerate the hip so that the individual can prepare the hip joint and the lower kinetic chain for weight acceptance. The concentric actions of the hip extensors are from 1 percent to 30 percent of the stance phase. They are actively enabling the trunk to maintain an upright posture and not jackknife as the individual initially contacts the ground surface. So, they help to accept the weight and then extend the hip.

Abductors. In terminal swing, the abductors prepare the lower extremity for contact, eccentrically helping to control the drop of the contralateral pelvis, and then concentrically raising the pelvis. Again, it is important for the movement of the pelvis to be minimal because if it becomes excessive, there will likely be hip and back pain when walking. The abductors also help to control the alignment of the femur in the frontal plane.

Adductors. The adductors are primarily low grade active, but through the gait cycle and at contact, they stabilize the hip and help to assist with extension. By stabilizing the hip, adductors are also a large component of the individual’s ability to put the foot where they want, each and every step. In the older population, this is a primary issue and places them at an increased risk of falling. Additionally, just after the toe-off process, adductors help to assist the hip flexors to initiate flexion.

Internal and external rotators. On a fixed femur, the internal rotators control the contralateral hemipelvis moving forward. The external rotators are active during the early stance to control the alignment of the femur. They also help to finalize advancement of the hemipelvis to prepare the foot for heel strike, which is important in the gait cycle.

Knee extensors. The knee extensors are active in the late stage of swing, to first prepare the foot and lower chain to accept contact of the ground, and second, after the initial ground contact with both eccentric and concentric activation, to maintain the knee extension through mid-stance.

Knee flexors. The knee flexors are active in the late swing, to eccentrically slow down the knee extension and prepare for foot contact. After the initial contact, the knee flexors help to assist with hip extension and getting the leg ready to extend so that the individual can toe-off and maintain gait speed, keeping the propulsion and momentum going. The knee flexors help to provide for knee stability and also minimally assist with knee flexion after toe-off; because it is such a powerful motion, it is just a minimal assistance in a normal gait.

Dorsiflexors. The dorsiflexors major activity is after initial heel contact, controlling the plantar flexion and pronation. Pronation at early stance is important to help the individual manage the ground. The dorsiflexors also provide some ankle stability at push-off (or toe-off). During the swing phase, the dorsiflexors concentrically help to clear the ground which again, is an issue in falling.

Plantar flexors. The plantar flexors first eccentrically control the tibial displacement and help prevent uncontrolled knee flexion and excessive dorsiflexion at pre-stance and early stance. Second, the plantar flexors provide stability for the foot. Lastly, the plantar flexors assist with toe-off propulsion.

Trunk anterior structures. Within an individual’s trunk, the anterior structures, such as the rectus abdominis, have low-grade activation but are primary throughout the gait cycle. This is also is true predominantly with the transverse abdominis. When the hip flexes, there is a burst of activity with the rectus abdominis with activation of the hip flexors early on to help to stabilize the pelvis and the spine.

Trunk posterior structures. Concerning the posterior structures of the trunk, the inner vertebral muscles provide a slight help to control the forward momentum of the trunk and prevent jackknifing, similar to the hip structure muscles. Pertinent for individuals in forward head or trunk flex posture, the back muscles are very inefficient in helping with the jackknifing process, because they are stretched and weak.

Trunk stabilizers and mobilizers. The trunk stabilizers control and limit movement; they maintain the neutral spine curve and are good at responding to postural changes. The trunk stabilizers also provide the neurological input regarding where the individual is in space at any point in time.  The trunk mobilizers are the large multi-segmental muscles that insert or originate on the thorax and possibly the pelvis respond to changes in the line of action on a level, now an unleveled, walking surface. They also respond drastically to the magnitude of any intrinsic load. Accordingly, if an individual is carrying something on their left side and suddenly missteps, the mobilizers are the muscles that respond collectively to maintain an upright posture. They also initiate movement and help to distribute the load.

Of particular importance in the mobilizers are the gluteus muscles, whose importance to the hip abductors and external rotators were detailed above. The latissimus dorsi and the multifidi are also important. The multifidi double as stabilizers, because of their thickness levels. The erector spinae also help as mobilizers, as do rectus abdominis and certainly the internal and external obliques, particularly with load transference.

Water Walking

Considerations

The next section will detail the characteristics of water walking (specifically, the biomechanics), the significant differences between land and water walking, and then the manner in which water walking can be utilized for functional improvements.

Years ago, it was widely thought that water and land walking where the same. But, studies have shown that there are big differences between the two. Today, therapists do not place a patient in the pool simply because they will have less pain while walking unloaded. Rather, and this is the first consideration regarding water walking, therapists use very specific points in the gait cycle while in water to facilitate improvements on land. The second consideration is the biomechanical issues involved in water walking. Pursuant to the two aforementioned considerations, these discussions are heavily dependent on medical studies, because therapists want to adequately utilize water as an efficient intervention, particularly for functional improvements.

When a therapist is transitioning a patient to water walking, they must consider three things. First, what benefit can the patient accomplish in water that they cannot on land? This is also pertinent for insurance purposes, i.e. why is water better than land in this part of the rehab process? Second, once a therapist has decided to put a patient into the pool, they must consider how to transition the patient out of the pool, which is critical. And then, thirdly, the therapist must consider what is trying to be accomplished, overall, in the water. Maybe, the patient is only able to comfortably walk in water, and so this is their exercise setting. Or, maybe, the therapist is trying to set a motor program to improve trunk rotation, which can be facilitated very well in water.