1. RESISTANCE SYSTEMS AND INJURY PREVENTION Module 2- Principles of Biomechanics

2. Definitions  Work= Force x Distance  Power= Work/Time  Power= (Force x Distance)/Time  Power=Force x Velocity

3. Sources of Resistance  Gravity  F=m x a  Inertia- toughest to change speed of motion When weight is held in static position or moved at constant velocity, it exerts constant resistance only in downward direction. However, any acceleration of the weight requires additional force  Free weights, body weight, weight stack machines  Most common source of resistance  Friction  F =k x F(n)

4. Sources of Resistance  Fluid Resistance  F = k x velocity  Elasticity  F = k x distance

5. Low Back Risk  Prevention  Flatten the back during the lift to stabilize the lumbar spine  Use a weight belt to increase intra-abdominal pressure to support the spine  Use a weight belt for heavy resistance exercises only  Caution  Don’t hyperextend the back  Be careful when using the valsalva maneuver. Anyone who has high blood pressure or CV disease should avoid the valsalva maneuver

6. Figure 4.15

7. Shoulders  The shoulder is prone to injury during weight training because of its structure and the forces to which it is subjected.  Warm up with relatively light weights.  Follow a program that exercises the shoulders in a balanced way.  Exercise at a controlled speed.

8. Knees  The knee is prone to injury because of its location between two long levers.  Minimize the use of wraps.

9. Reducing the Risk of Strength Training Injuries  Perform one or more warm-up sets with relatively light weights, particularly for exercises that involve extensive use of the shoulder or knee.  Perform basic exercises through a full ROM.  Use relatively light weights when introducing new exercises or resuming training after a layoff of two or more weeks.  Do not ignore pain in or around the joints.  Never attempt lifting maximal loads without proper preparation, which includes technique instruction in the exercise movement and practice with lighter weights.  Performing several variations of an exercise results in more complete muscle development and joint stability.  Take care when incorporating plyometric drills into a training program.

10. Stages of Tissue Healing  Inflammation (2-3 Days)  Pain, swelling, redness  Decreased collagen synthesis  Repair (2 Days-2 Months)  Collagen fiber production  Decreased collagen fiber organization  Decreased number of inflammatory cells  Remodeling (2-4 Months)  Proper collagen fiber alignment  Increased tissue strength

11. Rehabilitation and Reconditioning Goals and Strategies  Inflammation  Prevention of new tissue disruptions and prolonged inflammation with the use of relative rest and passive modalities  Function of cardiorespiratory and surrounding neuromusculoskeletal systems must be maintained  No active exercise for the injured area

12. Rehabilitation and Reconditioning Goals and Strategies  Repair  Prevention of excessive muscle atrophy and joint deterioration of the injured area  Function of the neuromusculoskeletal and cardiorespiratory systems must be maintained  Possible exercise options include: Submaximal isometric, isokinetic and isotonic exercise Balance and proprioceptive training activities

13. Rehabilitation and Reconditioning Goals and Strategies  Remodeling  Optimization of tissue function  Progressive loading of neuromusculoskeletal and cardiorespiratory systems as needed  Possible exercise options include Joint angle specific strengthening Velocity specific muscle activity Closed and open kinetic chain exercises Proprioceptive training activities