Gait stability: what makes your step secure – Knowledge

1. What this article covers

Gait stability is the ability to cope with disturbances while you walk. A disturbance can be a bump in the pavement, a push in a crowd or a misstep at a kerb. Your walking is stable if you carry on afterwards and stay upright.

This text answers four questions:

• What keeps you upright while you walk?
• How can gait stability be measured?
• What does the Lyapunov exponent, a measure from movement research, contribute?
• What improves gait stability?

One point of orientation belongs at the start. For training there are large randomised trials [23]. For the measures the picture differs. Walking speed and the variation from step to step are linked to falls in cohort studies [7], [8]. The Lyapunov exponent remains a research measure without reference values [16].

This article complements two others. How a falls assessment works is described in Assessing the risk of falling. Which programmes reduce falls is described in Fall prevention.

2. What gait stability means

Walking is a series of controlled near-falls. With every step your body falls forwards. The swinging leg catches it. The same process then starts on the other side.

Your centre of mass lies outside your base of support for most of that time. Quiet standing works differently. There the centre of mass lies above your feet. Walking therefore requires continuous control that standing does without [1].

In research, gait stability means: how well does your walking pattern return to itself after a disturbance [1]? A review from 2013 compared the measurement methods in use at the time [1].

2.1 Stability and variability are two different measures

Two terms are often mixed up. They measure different things.

• Variability describes how much your steps differ from one another. What is measured is, for example, the spread of step duration over a hundred steps.
• Stability describes how your body answers a deviation. What is measured is whether a disturbance becomes smaller or larger over the next step.

The difference has practical consequences. A very even walking pattern can still be sensitive to disturbances. And a certain amount of variation belongs to healthy walking. It allows you to adapt to uneven ground.

The 2013 review concluded that two measures have the best support: the variability measures and the short-term Lyapunov exponent [1]. For the long-term Lyapunov exponent and for several other methods the verdict was unfavourable [1].

3. How your body secures walking

Three senses provide the basis. Your eyes report where the ground is. Your balance organ in the inner ear reports rotation and acceleration of the head. Your position sense reports from joints, muscles and tendons where your limbs currently are.

From these signals your nervous system controls one quantity above all: where the next foot lands. Muscle strength at the ankle and the hip and the posture of your trunk come on top of that.

3.1 Sideways balance needs active control

Forwards and backwards, walking largely stabilises itself. The momentum of your body carries you over the standing foot. Sideways this does not apply. There the body topples away without control [2].

A study from the year 2000 showed this in 15 healthy young people [2]. With the eyes open, foot position varied 79 per cent more sideways than along the direction of walking. When walking with the eyes closed, sideways variation rose by 53 per cent and variation along the walking direction by only 21 per cent [2].

A practical rule follows. Anyone who is unsteady sideways needs exercises in the sideways direction. Side steps, crossover steps and narrow standing positions therefore belong in every balance programme.

3.2 The margin of stability at every step

For standing there is a simple rule. Your centre of mass has to lie vertically above the area between your feet. For walking this rule is not enough, because your body is moving.

A paper from 2005 extended the rule [3]. The velocity of the centre of mass is added to its position. This creates an imagined point slightly ahead of your actual centre of mass. How far that point sits from the edge of your base of support is called the margin of stability [3].

Walking faster requires a larger base of support to keep the same margin. That is why your steps get longer when you walk faster. And that is why a push from the side is more dangerous than a push from behind. Sideways your base of support is narrow.

4. Where walking goes wrong

A study in two long-term care facilities filmed and analysed 227 real falls [4]. The recordings came from 130 people with an average age of 78 years.

• Incorrect weight shifting was the most frequent cause: 93 of the 227 falls, that is 41 per cent [4].
• Tripping followed with 48 falls, that is 21 per cent [4].
• Hitting or bumping, loss of support and collapse each accounted for about 11 per cent [4].
• Slipping was rare: 6 of the 227 falls, that is 3 per cent [4].

The most frequent activity at the moment of falling was walking forwards, with 54 of the 227 falls [4]. Standing quietly followed with 29 falls and sitting down with 28 falls [4].

These figures come from care facilities. For people who live at home and go out they apply only in part. Outdoors tripping is more frequent.

In tripping, foot clearance plays a part. This is the smallest vertical distance between foot and ground while the leg swings forwards. A review of twelve studies found no age difference in the average of that distance [5]. What did differ was the variation from step to step. It was larger in older people, and larger in people with a history of falls than in people without [5].

For you this means: what matters are the individual unfavourable steps. Your average step says little about them.

5. What is measured in practice

The 2022 world guideline on fall prevention recommends a short screening for all older people [9]. It asks about falls in the past year, about unsteadiness while walking and about worry about falling [9]. Measurements come afterwards.

5.1 Walking speed is the simplest measure

You need a straight stretch and a stopwatch. What is measured is the time over four or ten metres.

An analysis of nine cohort studies with 34,485 people aged 65 and over put the value in context [6]. Average walking speed was 0.92 metres per second. Every 0.1 metres per second of faster walking went along with lower mortality [6]. Follow-up lasted 6 to 21 years.

The same holds for falls. In a study of 597 people aged 70 and over, 226 fell over an average of 20 months, that is 38 out of 100 [7]. Every 0.1 metres per second of slower walking went along with a fall rate about 7 per cent higher [7].

A caution belongs here. Walking speed describes differences between groups. For a single person it remains a probability. More on the accuracy of such tests is in Assessing the risk of falling.

5.2 The variation from step to step

What is measured is how much the duration or the length of your steps scatters around its own average. For this you need several dozen steps in a row.

A study of 52 people aged 70 and over compared this scatter with later falls [8]. About 40 per cent of the participants fell at least once in the following year. In them step duration scattered by an average of 106 milliseconds, in the others by 49 milliseconds [8].

This figure has limits. Fifty-two people took part, and the scatter within the falling group was wide. The groups therefore differ on average, and the values of individual people overlap considerably.

The larger study of 597 people found the same link [7]. Both the scatter of stride length and the scatter of swing time predicted falls, and did so on top of age, illnesses, medication and the usual balance tests [7].

5.3 Sensors measure in daily life rather than in the laboratory

An accelerometer on the lower back records how your trunk moves while you walk. From that signal, speed, stride length, regularity and stability measures can be calculated.

One study had 169 people with an average age of 75 wear such a sensor for a week [10]. Over the following six months 35 out of 100 people fell at least once [10]. Both the amount of activity and the quality of walking were linked with the falls [10].

A larger follow-up with 319 people confirmed this [11]. The predictive accuracy of the models lay between 0.66 and 0.76 [11]. A value of 0.5 corresponds to chance, a value of 1.0 to perfect separation. The models therefore sit between chance and certainty, closer to chance than to certainty.

One finding deserves attention. A study measured the same quantities in 18 older people once on a treadmill and once in daily life [12]. In daily life walking was more variable, less regular and less stable than on the treadmill [12]. For 14 of 32 characteristics the two measurements agreed. The stability measure was among those that did not agree [12].

For you this means: a measurement on a treadmill describes your walking on a treadmill. Your walking on the pavement can look different.

6. The Lyapunov exponent

The Lyapunov exponent is a measure from the mathematics of moving systems. It has been applied to human walking since the year 2000 [14]. In gait research it is also called local dynamic stability or divergence exponent.

6.1 The basic idea: how fast do small deviations grow?

Picture two moments in your walking. In both moments your joint positions and your velocities are almost identical. The two moments lie several steps apart.

Now follow both moments forwards. After half a step: how different have the two movements become? After a whole step: how different then?

The Lyapunov exponent states how fast that difference grows. A high value means that small deviations quickly become larger. A low value means that your walking recaptures small deviations. A high value therefore stands for less stability [1].

The calculation needs no artificial disturbance. It uses the small deviations that occur in any walking anyway. That is what makes the measure attractive for research. You can learn something about the answer to a push without pushing anyone.

Two values are calculated separately [1]. The short-term exponent describes the first half to whole step interval. The long-term exponent describes four to ten steps. The short-term value is the better supported of the two [1].

6.2 How the value is calculated

The path from the signal to the number runs in four steps.

1. Record. A sensor on the trunk or a camera system records several minutes of walking. What is captured is, for example, the acceleration of the lower back in three directions.
2. Build the state space. One signal is turned into several by placing the same signal next to itself with a time shift. A single curve thereby becomes a multidimensional path.
3. Search for neighbours. For every point on that path the nearest point from another step cycle is sought. These two points are the two almost identical moments.
4. Measure the divergence. For all neighbouring pairs it is measured how their distance grows over the following steps. The slope of that curve is the Lyapunov exponent.

The common calculation method dates from 1993 [13]. It was developed for short data series and is still the one most used in gait research.

The first application to walking appeared in 2000 [14]. It compared walking on the ground with walking on a treadmill. And it compared people with nerve damage from diabetes with healthy comparison participants [14]. One result of that work still holds: the treadmill makes walking more stable than it is on the ground [14].

6.3 What the value says about the risk of falling

The largest study on this examined 134 people aged between 50 and 75 [15]. They walked on a treadmill while a sensor on the trunk recorded. Afterwards they were asked about falls in the past year.

Both step variability and the short-term Lyapunov exponent were linked with the history of falls [15]. Both together explained more than either measure alone [15].

This study has one limitation that is decisive for its conclusion. Falls were asked about in the past, and the measurement came afterwards. Someone who has already fallen may walk differently. Whether the value predicts future falls is left open by this design.

The 2013 review ranked the short-term exponent as one of the two best supported methods [1]. For the long-term exponent the verdict was unfavourable [1].

In neurological conditions the value is being tested as well. A 2026 review on multiple sclerosis describes it as sensitive to early changes [22]. At the same time it states that clinical use remains open [22]. More about the condition is in Multiple sclerosis.

There are no reference values. A systematic review evaluated 102 papers [16]. The values differed so much with measurement site, calculation method, number of strides and walking speed that no comparison figure could be formed [16]. The review therefore called for a standard procedure before the measure moves into practice [16].

6.4 Where the value reaches its limits

Five limitations are well documented.

First, the value depends on walking speed. One study measured 15 healthy people at various treadmill speeds [18]. The short-term exponent fell along the walking direction as speed rose [18]. Sideways and vertically the relationship was curved [18]. Two people walking at different speeds can therefore hardly be compared directly.

Second, the value depends on the length of the measurement. The same research group showed that longer data series give more precise values [17]. Two measurements may only be compared if both cover the same number of strides [17].

Third, the value reacts sensitively to measurement noise. One study added noise to a computational model and observed large errors in the calculated exponent [19]. It concluded that at least 50 stride cycles are needed [19].

Fourth, repeatability depends strongly on the settings. One study had 15 young people walk on a treadmill three times and calculated the exponent from 18 different movement variables [20]. Five of those 18 variables reached very good agreement between measurements at 450 strides [20]. The same five remained usable at 60 strides [20]. For the remaining 13 this did not hold [20].

Fifth, showing a change requires many participants. One study calculated how many participants a trial needs to demonstrate differences in stability and variability measures [21]. With one measurement per person and condition the range went from 7 to 192 people [21]. Which number applies depends on the size of the expected difference [21].

The finding from section 5.3 comes on top of this. The stability value from the treadmill and the stability value from daily life were unrelated in the same people [12].

6.5 What this means for you

The Lyapunov exponent describes a genuine property of walking. It measures how well your nervous system recaptures small deviations within the ongoing step. That property is hard to capture with the simple tests used in practice.

For the treatment of a single person the value nevertheless remains without use today. Three things are missing: reference values [16], a standard calculation method [16] and studies that predict future falls rather than describe past ones [15].

If someone offers you a measurement of gait stability expressed as a single number, ask three questions:

• What do you compare my value with?
• How many strides were measured, and at what speed?
• What changes in my treatment depending on how the value turns out?

If the third question stays unanswered, the measurement changes nothing about your treatment. Training then follows what the training trials measured: your strength, your balance, your walking speed and your falls.

7. What improves gait stability

Here the evidence is considerably better than for the measures.

7.1 Strength and balance training is the foundation

The 2019 Cochrane review summarised 108 randomised trials with 23,407 participants [23]. Average age was 76 years, and 77 per cent were women.

Out of 1,000 people followed for one year, 480 in the comparison groups fell at least once [23]. In the training groups there were 72 fewer, with a confidence interval of 52 to 91 people [23]. The certainty of this statement is high [23].

The effect depends on the type of training [23]:

• Balance and functional exercises reduced the rate of falls by 24 per cent. The certainty of this statement is high [23].
• Several types of training combined, usually balance plus resistance training, reduced the rate of falls by 34 per cent. The certainty is moderate [23].
• Tai Chi reduced the rate of falls by 19 per cent. The certainty is low [23].
• Resistance training alone, dance and walking programmes without a balance component gave an uncertain picture [23].

Resistance training remains worthwhile nonetheless. The step that catches you requires strength in the calf and the thigh. More on this is in Strength training and Muscle weakness in older age.

7.2 Practising steps on a signal

In a trip, fractions of a second decide the outcome. Whoever places a step in time catches themselves.

A review summarised seven randomised trials with 660 participants [24]. What was practised were steps on a signal and steps arising out of a disturbance. The rate of falls in the training groups was 52 per cent lower than in the comparison groups [24]. The proportion of people with at least one fall was 49 per cent lower [24].

Reaction time, single-leg stance and the time in the Timed Up and Go improved [24]. Muscle strength was unchanged [24]. The effect arises through the speed of the response.

These figures come from seven small trials with 660 people in total. The Cochrane review covers 108 trials. Larger figures from few trials remain more uncertain than smaller figures from many.

7.3 Training with deliberate perturbations

In perturbation training a professional deliberately puts you off balance. They pull on a belt, push sideways at the shoulder or place a tripping obstacle in your path. On a treadmill the same is done through sudden changes of speed [26]. A safety harness catches you.

The idea behind it is simple. You practise exactly the movement that prevents a fall [26].

A 2026 review summarised 25 randomised trials with 2,659 older people [25]. The rate of falls was 23 per cent lower than in the comparison groups, and falls with injury 24 per cent lower [25]. Programmes with at least six hours of practice reached 33 per cent [25].

Two limitations belong with this. The review rated the certainty of this statement as low [25]. And the improvement showed mainly in catching the balance. On ordinary walking this training had little effect [25].

An earlier review from 2015 arrived at a similar picture with fewer trials [27]. In the trials, perturbation training comes in addition to strength and balance training. As a stand-alone programme it has hardly been studied.

7.4 Walking and thinking at the same time

Most falls happen in daily life, and in daily life you rarely walk with your full attention. You talk, carry something or look for your house key.

In dual-task training you practise both at once. You walk and count backwards. You walk and name words starting with a given letter. You walk and carry a tray.

A review with meta-analysis found better values for balance and mobility with this training than in the comparison groups [28]. For the effect on the number of falls the result was less clear [28].

8. Exercises for gait stability

The following exercises cover the building blocks from section 7. Stand next to a wall or beside a stable chair. Keep your hand within reach of the backrest.

Single-leg stance.

1. Stand on one leg. The other leg hangs free.
2. Hold for 20 to 30 seconds.
3. Change sides.
4. Do 3 rounds per side, on 5 days a week.

Sideways walking.

1. Take 10 steps sideways to the right.
2. Take 10 steps sideways to the left.
3. Cross the trailing leg once in front and once behind.
4. Do 4 rounds, on 3 to 5 days a week.

Walking with turns.

1. Walk 5 metres straight ahead.
2. Turn 180 degrees and walk back.
3. Change the direction of the turn every second time.
4. Do 10 turns, on 3 days a week.

Step on a signal.

1. Place four paper strips around you: front, back, right, left.
2. Have a second person call out a direction.
3. Place one foot on the named strip as fast as you can, then return.
4. Do 20 steps, on 3 days a week.

Walking with a thinking task.

1. Walk at your usual pace through an open space.
2. Count backwards from 100 in steps of three while you walk.
3. Walk for 2 minutes.
4. Do 3 rounds, on 3 days a week.

Two building blocks belong under professional supervision. Perturbation training needs a safety harness and a person who doses the disturbance. And anyone who has already fallen should have the causes assessed first.

A complete programme with fixed sets and repetitions is in Fall prevention. How to measure and change your step rate is in Running drills.

9. What you can observe yourself

You need no equipment for this. Pay attention to five points over two weeks.

• Do you keep your pace while talking? Someone who slows down or stops during a conversation divides their attention differently than before.
• How safely do you walk in the dark? Without vision, sideways control becomes harder [2].
• How often does your foot touch an edge? Count scuffs at carpet edges and door thresholds.
• Do you avoid certain routes? An avoided route is a signal, even without a fall.
• How often have you fallen in the past year? This question comes first in the guideline [9].

Write the answers down. In an assessment they are worth more than a recollection.

10. When to seek advice

Make an appointment with your doctor if one of these points applies:

• You have fallen at least once in the past year [9].
• You feel unsteady while walking [9].
• You avoid routes or activities because of your unsteadiness [9].
• Your walking has changed within weeks.

Go to the emergency department at once if your unsteadiness starts suddenly. This applies in particular together with dizziness, double vision, slurred speech, numbness or weakness in an arm or a leg. A stroke can be behind it. More on this is in Cerebellar stroke.

11. What you should know

• Gait stability is your body's answer to disturbances [1]. The evenness of your steps is a different measure.
• Sideways balance needs active control. With the eyes closed, sideways variation in foot position rose by 53 per cent and variation along the walking direction by 21 per cent [2].
• Incorrect weight shifting caused 93 of 227 observed falls in care facilities, tripping 48 and slipping 6 [4].
• In tripping, the variation in foot clearance counts. Its average did not differ between older and younger people [5].
• Walking speed is the simplest usable measure [6], [7].
• The variation from step to step predicts falls. In 52 people examined, step duration scattered by 106 milliseconds in those who later fell and by 49 in the others [8].
• Sensors in daily life predict falls with moderate accuracy. The models reached values between 0.66 and 0.76 on a scale from 0.5 to 1.0 [11].
• The Lyapunov exponent measures how fast small deviations in walking grow [1], [14]. A high value stands for less stability.
• The short-term exponent is linked with the history of falls [15]. Whether it predicts future falls is open.
• There are no reference values. A review of 102 papers found the values so varied that no comparison figure could be formed [16].
• The value depends on speed, measurement length, noise and settings [17], [18], [19], [20].
• Training reduces falls. Out of 1,000 people followed, 480 in the comparison groups fell at least once within a year. In the training groups there were 72 fewer [23].
• Balance and functional exercises have the best evidence, alone or together with resistance training [23].
• Step training and perturbation training add to the programme [24], [25].
• Your training follows strength, balance, speed and falls. A single laboratory number does not steer it today.

References

All Digital Object Identifiers (DOIs) were checked against the Crossref register. The links in the reference list lead through the DOI service to the publishers' websites. Some of these are located outside Switzerland and the EU. When you click, your IP address is transmitted to the respective provider. This does not happen on our own site.

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Transparency

• Authorship: Roger Hilfiker
• AI assistance: the literature search and the draft text were produced with Claude (Anthropic). Roger Hilfiker checked all statements, figures and sources and revised the text.
• Created: 27 August 2026
• Last updated: 27 August 2026
• Sources: the 28 papers in the reference list. All DOIs were checked against the Crossref register.
• How the sources were searched: queries of the Europe PMC database in August 2026 on gait stability, local dynamic stability, the Lyapunov exponent, gait variability, the margin of stability, sensor measurement in daily life, causes of falls, and strength, balance, step, perturbation and dual-task training. Where this text says that no study is available on a question, that refers to this search.
• Conflict of interest: our practice offers physiotherapy, gait retraining and fall prevention, and earns money from them. This text states a documented benefit for training. It also states that measuring gait stability as a single number remains without use for the treatment of an individual person today.
• Funding: Physiotherapie Tschopp & Hilfiker, 3902 Glis. The article was produced with the practice's own resources.
• Next review: 27 August 2028. We also revise this article on a rolling basis whenever new articles are added. That happens about every two months.