Human Gait

Human gait analysis is an essential tool in rehabilitation, neurology, orthopedics, physiotherapy, and movement sciences. The way a person walks reflects the functional state of their musculoskeletal and neurological systems, making it a key indicator of balance, stability, and fall risk.

Digital sensor–based analysis, particularly using mobile phones, is transforming clinical assessment by enabling gait measurement that is fast, objective, and extremely low-cost as Balanced Gait Test.

1. What is human gait?

Human gait is a cyclical process through which the body moves forward while maintaining balance thanks to a coordinated sequence of movements.
It is a quasi-periodic phenomenon that occurs with some imprecision and therefore must be studied using statistical methods. Although walking appears to be automatic, gait depends on complex interactions between:

  • the central and peripheral nervous systems,
  • balance control mechanisms,
  • muscle strength and coordination,
  • proprioception, vision, and the vestibular system.

Alterations in any of these systems can affect gait and increase the risk of falls, especially in older adults or neurological patients.

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2. Gait phases

Each gait cycle has two main phases:

  • Stance phase (approx. 60%)
  • Swing phase (approx. 40%)

There are also two periods of double support during the cycle, when both feet are in contact with the ground. The duration, symmetry, and consistency of these phases are key indicators of gait quality.

You can find a detailed explanation of these phases, along with accelerometry-based diagrams, in the Balanced Gait Test user manual.

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3. Fundamental parameters of gait analysis

To describe human gait, a wide range of parameters is commonly used. The most relevant include:

3.1 Cadence

Number of steps per minute. It is associated with functional walking speed and efficiency.

3.2 Step length and step time

Each step should be relatively consistent. Unexpected variations may indicate instability.

3.3 Gait variability

Step-to-step variability is one of the most important indicators of stability. It is associated with:

  • fall risk,
  • neurological disorders,
  • aging,
  • frailty.

The classic work by Hausdorff (2005) describes how temporal fluctuations in gait show complex patterns that are highly sensitive to disease.

3.4 Symmetry

Right vs. left. Marked asymmetry often appears in:

3.5 Homogeneity

The stable repetition of the same step pattern. Poor homogeneity indicates reduced coordination or irregular motor control.

3.6 Three-dimensional accelerations

A smartphone accelerometer records:

  • vertical acceleration,
  • antero-posterior acceleration (forward propulsion and braking),
  • medio-lateral acceleration (right–left balance).

These signals allow estimation of stability, heel-strike impact, applied force, and the regularity of the gait pattern.

4. Gait Variability and Fall Risk

One of the strongest conclusions in the scientific literature is that excessive gait variability predicts falls better than walking speed or step length.

Studies by Hausdorff and colleagues show that:

  • highly variable gait is associated with neurological disorders,
  • individuals with greater variability are more likely to fall,
  • even when walking speed is normal, variability can reveal hidden instability.

These findings make variability a key parameter in clinical gait assessment.

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5. What does Balanced Gait Test measure?

5.1 Traditional instrumented systems

These include:

  • Optoelectronic camera systems (Vicon, Qualisys, OptiTrack)
  • Force plates
  • Full gait laboratories

They are considered the gold standard, but they require:

  • expensive equipment,
  • specialized personnel,
  • dedicated space,
  • significant analysis time.

5.2 IMU-based wearables

Accelerometers, gyroscopes, and magnetometers placed on the feet, legs, or pelvis.

They provide:

  • fast analysis,
  • measurement outside the laboratory,
  • high temporal resolution.

Commercial examples: BTS G-Walk, APDM Opal.

5.3 Smartphone-based gait analysis

Modern smartphones include high-quality three-axis accelerometers. Their use makes it possible to:

  • analyze gait from a single measurement,
  • reduce the cost to practically zero,
  • perform repeated evaluations,
  • monitor progress on a daily basis.

Balanced Gait Test is an example of this new generation of tools.

6. What does Balanced Gait Test measure?

Balanced Gait Test uses the smartphone’s accelerometer to measure gait objectively. Its algorithm identifies the phases of the gait cycle and calculates:

  • 16 symmetry and homogeneity parameters,
  • cadence,
  • step power,
  • Balance Degree, a global value between 0 and 100.

The system is described in detail in the instrument’s technical manual.

In addition, it uses robust methods inspired by the scientific literature to identify representative repetitions and exclude irregular ones, following ideas such as those proposed by Sangeux and Polak (2015) for selecting representative strides.

This combination makes it possible to:

  • enable remote monitoring in rehabilitation programs.
  • evaluate gait in under one minute,
  • obtain quantitative values that are comparable across sessions,
  • track clinical evolution over time,
7. Clinical applications of gait analysis

Gait analysis is currently used in several clinical areas:

7.1 Neurology

  • Parkinson’s disease
  • Alzheimer’s disease
  • Multiple sclerosis
  • Neuropathies
  • Stroke

7.2 Traumatology

  • Knee injuries: ACL, meniscus
  • Hip or knee prostheses
  • Ankle or tibial fractures

7.3 Geriatrics

  • Frailty
  • Fall-risk assessment
  • Stability monitoring

7.4 Rehabilitation and Physiotherapy

  • Measurement in real-life environments, not only in the clinic
  • Evaluation of therapeutic progress
  • Comparison between sessions