Muscular Strength. & Endurance. Types of Muscular Contraction. Muscular Strength. Muscular Endurance. Muscular Power

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1 Muscular Strength Muscular Strength & Endurance The greatest amount of force that a muscle, or muscle group, can produce in a single maximal effort. Muscular Endurance The ability of a muscle group to perform repeated contractions against a sub-maximal load for an extended period of time. Muscular Power The ability to produce force quickly. Power can be calculated by multiplying the force of the muscular contraction by the speed of contraction (force x velocity). Types of Muscular Contraction Isometric Exercise (static contraction) 1

2 Isotonic Exercise (constant resistance) Concentric Contraction Isokinetic Concentric Eccentric Contraction Cybex Muscle Mechanics Force and Torque Production The force output of a muscle is obviously determined in part by the state of training (muscle size and recruitment patterns). However, many other factors will affect the eventual torque output of a muscle-joint system. Force-Length Curve of Skeletal Muscle Data from Edman, Concentric Tension Lo Length of Contractile element Eccentric 2

3 Power = Force x Velocity Optimal Power Maximum power occurs at about 1/3 maximal velocity of shortening and about 1/3 maximum concentric force? Force Velocity Force Power Athletes must find as high a level of power output as possible that can be sustained for the duration of their event. Forearm Flexion Torque Force Force can be equal but moment arms are very different 80 Torque vs. Angle Forearm Flexion Torque Angle

4 Knee Extension Constant Resistance Exercises Torque Angular Velocity Variable Resistance (leverage {force x distance}) Variable Resistance torque (leverage) = force x perpendicular distance 50kg 50kg Max torque Barbell Nautilus Redrawn from Smith,

5 Variable Resistance Isokinetic Machines e.g. hydra -fitness Isokinetic Eccentric & Concentric Machines versus Free Weights Advantages of Machines Safety is easier to achieve with machines. Less skill required (no coaching = cheaper) Program design flexibility is higher (debatable?) The pattern of resistance can also be designed into a machine. Changing weights can be quicker and easier with the insertion of a pin in a weight stack or moving a dial on an isokinetic machine as compared to mounting plates on a bar (some gyms have many barbells already set up) Advantages of Free Weights Free weight exercises are usually performed in the standing position, which taxes a greater portion of the body s musculature than machine exercises. Free weights also require the use of additional musculature to stabilize the body part(s) being exercised. More skill is required to control the weights (benefit rather than a negative?). Lifting free weights often involves the more natural coordination of several muscle groups. They can simulate real life activities better than machines. 5

6 Twitch Response Muscle Fibre Types Tension Fast Twitch (FT) Fiber Slow Twitch (ST) Fiber Slow Twitch Fast Twitch Fiber Type I Type IIa Type IIb Slow, oxidative Fast, oxidative, glycolytic Fast, glycolytic Characteristics SO FOG FG Motorneuron size Small Large Large Muscle fiber diameter Small Large Large Speed of contraction Slow Fast Fast Strength of contraction Low High High Aerobic capacity High Medium Low Capillary density High Medium Low Myoglobin content High Medium Low Anaerobic capacity Low Medium High Peak Torque (Nm/kg body weight) Knee Extension Velocity (degrees/sec) Peak Torque (Nm) Knee Extension (80 o /second) Runners 800m Number of Contractions Percentage Slow Twitch Fibres Cross Country Skiers Cyclists Shot putters/disc throwers Untrained Long & High Jumpers Javelin Throwers Sprinters Percentage Fast Twitch Fibers 6

7 Event Slow Twitch (I) Fast Twitch (IIa and IIb) 100-m sprint Low High 800-m run High High Marathon High Low Olympic Weightlifting Low High Barbell Squat High High Soccer High High Field Hockey High High Football Wide Receiver Low High Football Lineman High High Basketball Low High Distance Cycling High Low Hereditability of Fibre Types Percent Slow Twitch Fibres Twin A Identical Twins Twin B Twin A Fraternal Twins Twin B Muscle Cross Sectional Area Adaptations to Resistance Training Do we get stronger by getting bigger? Hypertrophy - an increase in the size of cells such as muscle fibres. Hyperplasia - an increase in number of cells, such as muscle fibres Hypertrophy & Hyperplasia There is no strong research evidence showing hyperplasia can occur in adult humans. 7

8 General Body Composition Changes Little or no change in total body weight Significant loss of fat Significant gain in lean body mass Possible reduction in some girths and an increase in others Strength vs Age & Gender Male vs Female Hypertrophy The Concept of Average Males Females 8

9 Why are males stronger? Physically larger. Difference in body composition. Body proportion differences # of push ups Active males Inactive males Active females Inactive females Cultural factors? Age (Years) # of leg lifts Active males Inactive males Active females Inactive females Age (Years) Strength vs Cross-Sectional Area Arm Flexor Strength (kg) Cross Sectional Area (cm 2 ) Males Females Muscular Strength and Endurance Training Variables and Program Design Developing a Successful Resistance Training Program The Overload Principle Principle of Progressive Resistance two-for-two rule Principle of Arrangement of Exercises Principle of Specificity (Training for Strength, Size, Endurance or Power) 9

10 Program Design Definitions Prime Movers or Target Muscle Muscle(s) primarily responsible for the movement Synergists or Assistors Dynamic Stabilizers Muscles that assist the prime mover Muscles stabilizing the limbs moving (typically these are two joint muscles that would be lengthening across one joint and shortening across the other (therefore the net result is little change in length) Stabilizers Muscles that stabilise adjacent body segments or contract with no appreciable movement Equipment Use equipment that is easily accessed. Free weights (safety and time issues?) Weight-stack machines (stabilizers, skill?) Rubber bands (feedback?) Isokinetic machines (cost?) Sets and Reps (Heyward) 100% 95% 90% 85% 80% 75% 70% 65% 60% You need to design a program that meets the following criteria: fits your skill level (equipment) fits your program needs (strength, hypertrophy, endurance) targets major muscle groups targets additional muscle groups (if needed, e.g. forearms for tennis players) fits your desired time commitment (equip.) is safe!! Order of Exercises The same muscle groups should not be exercised consecutively unless you have adequate recovery periods. Exercise small muscle groups last. Do not strength train the same muscle groups on consecutive days. Sets and Reps (Poliquin, 1986) = 1-RM = 2-RM = 4-RM = 6-RM = 8-RM = 10-RM = 12-RM = 14-RM = 15- to 20-RM 100% = 1-RM 95% = 2-RM 90% = 3-RM 88% = 4-RM 85% = 5-RM 83% = 6-RM 80% = 7-RM 78% = 8-RM 76% = 9-RM 75% = 10-RM 72% 70% 69% 68% 66% 65% 64% 63% 62% 60% = 11-RM = 12-RM = 13-RM = 14-RM = 15-RM = 16-RM = 17-RM = 18-RM = 19-RM = 20-RM The higher the repetition the less accurate the percentage. 10

11 A Basic Program 1. Leg Press 3 sets reps 2. Bench Press High Lat Pull-down Leg Curl Military (seated) Press Back Extension Two-arm Curl Bent Knee Sit-ups Another Program (free weights) 1. Back or Front Squat Bench Press Pull-Ups Deadlift (back and hamstrings) 5. Standing Shoulder Press (Push Press) 6. Seated Row Bent Knee Sit-ups Dumbbell Superset Sessions Dumbbell Bench Press Dumbbell Bent-Over Row Back Extension or Dumbbell Straight Leg Deadlift Bent Knee Sit-ups Dumbbell Shoulder Press Pull-Up (or Lat-Pull) or Dumbbell Pullover Dumbbell Lunge Dumbbell Bicep Curl Dumbbell Triceps Extensions (or Kickback) Callisthenics/Home Workouts Strength Training Resistance Training Programs Number of exercises: 1-2 per muscle group Weight load: 80-90% 1RM Sets: 1-4 sets per exercise Repetitions: 2-5 repetitions per set Rest between sets: 3 minute minimum 11

12 Strength/Hypertrophy Number of exercises: 2-4 per muscle group Weight load: 80-85% 1RM Sets: 2-5 sets per exercise Repetitions: 6-8 repetitions per set Rest between sets: 2-3 minute minimum Hypertrophy Number of exercises: 3-5 per muscle group Weight load: 70-80% 1RM Sets: 3-6 sets per exercise Repetitions: 9-12 repetitions per set Rest between sets: 1-2 minutes maximum Endurance Number of exercises: 1-2 per muscle group Weight load: 60-70% 1RM Sets: 1-3 sets per exercise Repetitions: repetitions per set Rest between sets: 1 minute maximum Fibre Type Involvement Percentages of 1RM Frequency Variable Response to Different Programs Varies with the type of program. General guidelines are for 2 to 3 sessions per week. More sessions can be done using split routines where you work different body parts on alternate days (e.g. Monday & Thursday - legs, back, biceps, abdominal; Tuesday & Friday - chest, shoulders, triceps). 12

13 Isokinetic Training Specificity! One Consistent Research Finding Strength Variety! Vary your program frequently ( every weeks?) Strength Periodization See link on Kin 143 webpage Resistance Training Periodization Every day? Eccentric Loading Delayed Onset Muscle Soreness (DOMS) 13

14 Sample Circuit Training Program Bench Press Bent-knee sit-up Leg extension Lateral pull-down Back extension Standing press Arm curl Toe raise Leg curl Triceps extension Leg press Upright row Intensity 40-55% 1-RM Repetition: max in given time (30 s) Rest: 15 s Time/circuit: 9 min Circuits/session: 3 min Time/session: 27 min Frequency: 3 per week Duration: 8 weeks Overload: adjust as 1-RM changes Equipment: machines Strength Training Misconceptions Women will bulk up and look unattractive Resistance-training slows you down Marathon workouts I haven t got the time to go to the gym for two hours You become muscle bound Protein supplements are necessary for strength gains Muscle will convert to fat after I stop training Avoiding Injury During Weight Training Ergogenic Aids Covered in lab More discussion in the Nutrition for Active Living and Athletes lecture Anabolic Steroids Drugs that resemble androgenic hormones such as testosterone. ANABOLIC refers to protein synthesizing effects ANDROGENIC refers to male secondary sexual characteristics 14

15 Potentially Harmful Side Effects of Anabolic Steroids liver damage (jaundice, cancer) coronary heart disease (increased blood pressure, increased serum lipids) testicular atrophy acne increased aggressiveness masculinization of women damage to growing children Sample Exam Question Name this weight training exercise. What joint movements are required to perform this movement? Which muscles are the prime movers? What are the safety issues associated with this exercise? Muscles Target: Latissimus Dorsi Synergists Brachialis, Brachioradialis, Biceps Brachii, Teres Major, Deltoid, Posterior, Infraspinatus, Teres Minor, Rhomboids, Levator Scapulae, Trapezius, Lower and Middle, Pectoralis Minor. Dynamic Stabilizers Triceps, Long Head Wide Spray Technique Do not name every muscle you can think of you will loose marks for incorrect answers! Please be specific. Keep you answers brief yet focussed! Strength Testing You can do this by trying to lift your maximum weight and if you can do 2 reps, wait for a few minutes and try a heavier load etc Safer: Choose weight you can bench press or leg press about 5 or 6 times until momentary muscular failure and use equation below to estimate your 1- RM. Use for reps 1 to 10. Higher numbers of reps = larger error in 1-RM estimate. 1-RM = (weight lifted)/[ (reps x )] From: Brzycki, M. (1993). Strength testing - Predicting a one-rep max from a reps-to-fatigue. Journal of Physical Education, Recreation and Dance 64 (1), Muscular Endurance Testing Curl-ups Push-ups or modified push-ups We will perform these in lab. 15