Operations Management and Strategic Management · Control Measures - Time and Motion Study, Method Study, Work Study

Motion Study and Principles of Motion Economy

Updated 10 October 2026 · Fact-checked

Motion study is the careful analysis of the body movements a worker uses to do a job, so that wasteful movements can be removed. Frank and Lillian Gilbreth broke motions into basic elements called therbligs. The principles of motion economy then guide a better method: fewer, simpler, easier movements.

Understand Motion Study and Principles of Motion Economy

Motion study looks at the movements of a worker's hands, arms, eyes and body while doing a task. The aim is to find movements that add no value, remove them, and arrange the rest in the easiest and quickest sequence. It is a part of method study, which in turn sits inside work study.

The idea comes from Frank and Lillian Gilbreth. They filmed workers and studied the films frame by frame. They found that any manual job can be broken into a small set of basic movements. They called these therbligs (the name is Gilbreth spelt almost backwards). Examples are search, find, select, grasp, transport loaded, position, pre-position, assemble, use, disassemble, release load, inspect, plan, hold, rest and avoidable delay.

Therbligs fall into two broad groups. Effective (productive) therbligs move the job forward: reach, grasp, move, position, pre-position, assemble, use, disassemble, inspect and release load. Ineffective (non-productive) therbligs do not add to the work: search, select, plan, hold, rest and avoidable delay. Motion study tries to shorten the effective ones and eliminate the ineffective ones. Some books classify a few therbligs, such as hold or inspect, differently, so follow the grouping given in your study material if the question asks for it.

The principles of motion economy are the practical rules that come out of this study. They are usually grouped under three heads: use of the human body, arrangement of the workplace, and design of tools and equipment. Following them reduces fatigue and raises output without making the worker work harder.

Motion study is done by direct observation, by films or video, or by tools like the SIMO chart (simultaneous motion cycle chart), which records the therbligs of both hands against a common time scale. A SIMO chart is prepared from a micro-motion film study. Micro-motion study uses film to study very short, repetitive jobs. Memo-motion study uses slow-speed filming (for example, one frame per second or slower) for long operations.

Key rules to remember

Therblig groups: Therbligs = Effective (productive) + Ineffective (non-productive); Effective: reach, grasp, move, position, pre-position, assemble, use, disassemble, inspect, release load. Ineffective: search, select, plan, hold, rest, avoidable delay. Aim: shorten the first, eliminate the second.
Principles of motion economy: three heads: Human body + Workplace layout + Tools and equipment; Write every principle under one of these three heads in an answer.
Human body principles: Both hands start and end together; arms move in opposite, symmetrical directions; hands not idle except in rest; Use the lowest classification of movement that does the job (fingers, then wrist, forearm, upper arm, shoulder, body). Smooth curved motions are better than sharp straight-line changes of direction.
Workplace principles: Fixed place for tools and materials; tools and materials pre-positioned and within normal working area; Use gravity feed bins and drop delivery, proper lighting and a chair of the right height.
Tools and equipment principles: Combine tools; pre-position tools; share load among fingers by their strength; Use jigs and fixtures to hold work; use foot-operated devices to free the hands.

How to solve Motion Study and Principles of Motion Economy questions

Use this order for any question on motion study or principles of motion economy, theory or case-based.

1Define motion study in one line and place it within method study and work study.
2Name the Gilbreths and explain therbligs, giving at least five examples.
3Separate the therbligs into effective and ineffective groups, as the question demands.
4For a given job, list the motions in sequence and mark each as effective or ineffective.
5Pick the ineffective motions and suggest how to remove or combine them, linking each fix to a named principle of motion economy.
6Group the principles under human body, workplace and tools and equipment.
7Write the improved method and state the benefit: less fatigue, less time, higher output.
8Close with a one-line conclusion on the aim of motion study.

Quickest way: Three-head principle recall

When to use it: Use when the question asks for principles of motion economy or for improving a given job in a short time.

Draw three columns in rough: Body, Workplace, Tools.
Put two or three keywords under each, such as both hands together under Body, fixed places under Workplace and jigs under Tools.
For an MCQ, check whether the word is an ineffective therblig (search, hold, rest, delay, plan, select) and eliminate it.
For a case question, tick each motion as effective or ineffective and attack the ineffective ones first.

Common mistakes in Motion Study and Principles of Motion Economy

Treating motion study and time study as the same thing.
Both appear in the same chapter and both involve watching a worker.
Fix: Motion study improves the method by removing wasteful movements. Time study measures the time for a job. Motion study is part of method study; time study is part of work measurement.
Calling hold or rest an effective therblig.
Students think anything done during the job helps the job.
Fix: Remember that hold, rest, search, select, plan and avoidable delay do not move the job forward. Treat them as ineffective and try to eliminate or reduce them.
Listing principles in random order without grouping.
Students memorise a long list of points.
Fix: Group under human body, workplace and tools and equipment. It reads clearly and earns structure marks.
Writing therbligs as the name of a person or a machine.
The word sounds unfamiliar.
Fix: State that a therblig is a basic elementary motion unit, named after Gilbreth with the letters nearly reversed.
Suggesting improvements without linking them to a principle.
Students give common-sense answers.
Fix: After each suggested change, name the principle that supports it, for example pre-position tools to avoid search and select.

Worked examples

Example 1

A packer at a Pune unit works as follows: searches for a carton, selects a carton, grasps it, moves it to the table, holds it with the left hand while the right hand packs items, and waits as the pile of items is brought from a distant rack. Classify the motions as effective or ineffective and suggest improvements using principles of motion economy.

Show the solution

Effective therbligs: grasp, move (transport loaded) and pack (use). They advance the work.
Ineffective therbligs: search, select, hold and waiting. They add no value. The wait is a delay caused by poor layout, because the items are kept at a distant rack.
Search and select: give cartons a fixed place in a bin near the packer, so materials are pre-positioned. This removes both motions.
Hold: use a fixture to hold the carton so the left hand is free. This follows the tools principle of using jigs and fixtures to hold work, and it lets both hands work together.
Delay: reposition the items within the normal working area, for example in a gravity feed bin, so the worker does not wait for supply. This is a workplace principle.
Resulting method: both hands reach, grasp, move and pack with no idle hand, search or delay.

Answer: Effective: grasp, move, pack (use). Ineffective: search, select, hold, and the wait caused by poor layout. Remove them through fixed pre-positioned carton bins, a holding fixture, and items repositioned in a gravity feed bin within the normal working area.

Example 2

Explain the principles of motion economy under their three heads, with two points under each.

Show the solution

Define the aim: to reduce fatigue and wasteful movement and raise output.
Human body: both hands should begin and end their motions together and should not be idle except during rest.
Human body: arm motions should be symmetrical and in opposite directions, and the lowest classification of movement that does the job should be used.
Workplace: there should be a definite fixed place for all tools and materials, and they should be placed within the normal working area.
Workplace: use gravity feed bins and drop delivery, and provide proper lighting and a chair of suitable height.
Tools and equipment: combine two or more tools into one and pre-position tools so they are ready for use.
Tools and equipment: use jigs, fixtures or foot-operated devices so the hands are free for productive work.

Answer: Human body: both hands start and finish together, symmetrical opposite arm motions. Workplace: fixed places for tools, items in normal working area. Tools and equipment: combined and pre-positioned tools, jigs and fixtures to hold work.

Exam tips

Define therbligs and give at least five with their effective or ineffective type. Examiners reward the classification.
Always group principles of motion economy under body, workplace and tools. This gives a clear structure in a 14-mark answer.
In a case question, show the original motion list first and the improved list after it. Both lists carry step marks.
For MCQs, check whether the item belongs to method study or work measurement. Motion study belongs to method study.
Mention the SIMO chart or micro-motion study in one line if the question asks how motion study is done.

Practice questions from Control Measures - Time and Motion Study, Method Study, Work Study

Motion Study and Principles of Motion Economy: frequently asked questions

What is a therblig?

A therblig is a basic elementary motion used in a manual job, as defined by Frank and Lillian Gilbreth. Examples are reach, grasp, move, position, use, hold and search. Breaking a job into therbligs helps to find wasteful motions.

What is the difference between motion study and time study?

Motion study analyses the movements of the worker to find a better method. Time study measures the time a qualified worker takes for a job to set a standard time. One improves the method, the other measures the work.

Which therbligs are ineffective?

Search, select, plan, hold, rest and avoidable delay are treated as ineffective because they do not directly advance the work. The aim is to eliminate or shorten them.

What is a SIMO chart?

A SIMO chart is a simultaneous motion cycle chart. It records the therbligs performed by both hands of a worker against a common time scale, and it is prepared from a micro-motion film study. It shows where the hands are idle or doing ineffective motions.