Assessing Muscular Strength PDF

Assessing Muscular Strength Key Terms  Muscular strength  The ability of a muscle group to produce maximal contractile force against a resistance in a single contraction  Muscular endurance  The ability of a muscle group to exert submaximal force for an ext...

Assessing Muscular Strength Key Terms  Muscular strength  The ability of a muscle group to produce maximal contractile force against a resistance in a single contraction  Muscular endurance  The ability of a muscle group to exert submaximal force for an extended period  Muscular Strength Jump to 30 sec Multiple Repetition Maximum © 2017 Pearson Education, Inc. Muscular Endurance Ridiculousness Muscular Contractions  Isometric contraction  No visible movement of the joint despite a muscular contraction  Dynamic contractions – visible movement of the joint (concentric and eccentric)  Isotonic contraction (same tension) – the same external resistance used throughout the contractions  Isokinetic contraction (same velocity) – maximal contraction against a constant velocity throughout the ROM Muscular Strength  Amountof force muscle can generate is based on:  Size of the muscle (primary factor)  The larger the muscle, the greater the force produced  Number of muscle fibers recruited during a movement  Themore fibers that are stimulated, the greater the force generated Muscle Fiber Recruitment and Muscular Force © 2017 Pearson Education, Inc. Skeletal Muscle Fibers Types  Slow-twitch fibers (type I)  Contract slowly  Generate little force, but are highly resistant to fatigue  Fast-twitch fibers (type IIb or type IIx)  Contract quickly  Generate a lot of force, but fatigue quickly  Intermediate fibers (type IIa)  Serve as a combination of the other two types  Contract rapidly, produce high force (less than IIx), and resist fatigue Recruitment of Muscle Fiber Type Dynamic strength testing  Force plate measurement “gold standard”  Advantage – offers direct measurement of exact forces and timing of forces  Disadvantages – expensive, usually limited to research, and often requires programming knowledge and data analysis  1 repetition maximum (1RM) testing  The most weight that can be lifted for one complete repetition  Very widely used as a valid measure of muscular strength in research, fitness facilities, and strength and conditioning programs  Advantages  A good measure of maximal strength for practical strength exercises  Can be translated to %1RM for exercise prescription purposes  Can be performed in most fitness facilities  Disadvantages  May not be appropriate for all populations  A reflection of the weakest part in the ROM Force Plate Data Dynamic Endurance Tests  Repetition maximums at a given weight to estimate 1RM  Perform as many repetitions until failure (usually below 10 or 12 reps)  Use a formula to calculate  Ex: 1RM = weight lifted (lb) / [1.028 – (reps to fatigue x.0278)]  Can also be used pre-post test  Improvement shown if increased reps at given weight Dynamic Endurance Tests  YMCA Bench Press Test  Perform barbell bench press at 30 reps/min  Men use 80 pounds, women use 35 pounds  Test terminated when cadence cannot be kept YMCA Bench Press  Relative Dynamic Endurance Tests  Maximum pushup test  Person performs as many pushups as possible  Procedures by ACSM - > Relative Dynamic Endurance Tests  Maximum pull-up test  Person lifts their body weight over a bar with a pronated grip  Some modified tests may use supinated grip  Other modifications using incline board with a pullup have been used as well  Flexed arm hang  Person holds themselves over pullup bar in hang position for maximal time Core Endurance/Stability Tests  Trunk curl test  Person lies flat with knees bent at 90 degrees  They curl the trunk keeping the fingertips flat to the floor moving forward and backward at 20 curls-ups/min  Must move forward and backward 12 cm (8cm over 45) marked by tape on the floor  NOTE: Some research suggests the test may not be related to strength/endurance  Maximal plank test  The person holds a plank (elbow) until volitional fatigue or fatigue results in improper form  Curl Up Test © 2017 Pearson Education, Inc. Sahrmann Core Stability Test  Uses a series of 5 movements to evaluate core stability  Can utilize blood pressure cuff or special device under the low back to monitor changes in pressure Isokinetic Dynamometer Isokinetic Dynamometers  Provides accommodating resistance as force increases to create a constant velocity  Able to determine peak forces at different portions of the ROM  Different speeds/protocols can be used to examine strength, endurance and power  Expensive and mostly only used in research Isometric Dynamometers Isometric Dynamometers  Handheld (push/pull) Dynamometers  Person pushes as hard as they can isometrically against the device using the intended muscle group  Can be used easily and is portable  Has good validity and excellent reliability  Moderately inexpensive ($200-1,000) Isometric Dynamometers  Grip Strength Dynamometer  Person squeezes as hard as they can against the dynamometer  Can be correlated with strength but may not translate  Spring-loaded dynamometer  Can be used to determine leg and back strength  Change in trunk angle and procedure Electromyography  Measures electric activity in the muscles  In theory, is linked to muscle activations (% of fibers activated)  Does not directly measure strength  Correlated to strength and force production  In many cases, requires a maximum voluntary contraction to compare different lifts to  Analyze % of recruitment activated  Expensive equipment used mostly in research  Usually used in conjunction with some other measure (external forces such as weight or a 1RM, force plates, etc…) Most Accurate/Useful Measures For Testing Strength/Endurance  Practical Application (multi-joint)  1RM Testing (strength)  Multiple RM (endurance)  Force Timing  Force Plates  Isokinetic Dynamometers  Muscle Recruitment  EMG