Springs are used to resist or assist muscular forces and produce joint movement. A spring is a coil of wire that can be elongated when a force is applied to one end. The amount a spring stretches is directly proportional to the applied force. Springs are rated by weight in pounds based on the wire material, thickness, and coil diameter. When the applied force is removed, the spring returns to its original length through stored potential energy converting to kinetic energy. Springs arranged in parallel require double the force to stretch the same amount as one spring, while springs in series require half the force but stretch twice as far.

1. SPRINGS
• DEFINATION:
The spiral springs are used to either
resist or to assist the force of muscular
contraction OR to produce passive movement of
joints.
FORMATION:
A spring is consist of a uniform coil of
wire which is extensible .

2. The Extensibility Of Spring:
A spring can be elongated by a
force applied at one end in the direction of its long axis , the
other end is being fixed
The increase in the length is directly
proportional to the magnitude of force
Weight of Spring:
 Springs are graded in pounds 40lbs,20lbs
 A tape is inserted within spring ,the tape become taut when
maximum length is reached .
 Weight of a spring is determined by
1. The material of wire
2. Thickness of wire
3. Diameter of coils

3. The Recoil:
 when applied force is removed the spring will return to
its original length
 Potential energy is stored during extension
 Kinetic energy is released when spring return to its
original length
Oscillatory movements:
if a weight applied to a stretch a
spring is raised and then released again oscillatory
movement is produced ,the amplitude of which decrease
progressively until it comes to rest

4. Spring used In Parallel
 When a spring of a specific weight is not available two
springs of half the required weight may be used in
parallel
 Two 40-lb springs arranged in parallel act as 80-lb
 In the case of two parallel springs double force in
required to elongate springs
 In parallel the springs extend half the
amount compared to what
would have happened with just one.
For 40-Ib springs arranged in parallel ,
80-Ib force is required

5. Springs used in series
 The weight of two equal springs arranged in series
act as a single spring.
 In this case half force is required to elongate springs.
 Each of two springs are only half extended.
The amount by which they must be extended in order
to reach its limit of extension is double.
For 40-Ib springs arrange in
series 20-Ib force is required