Methods of Resistance Training I PDF

Methods of Resistance Training I Resistance Training: Science & Application EXSC216 Dr Jonathon Weakley Learning Outcomes What is muscular strength? What is muscular power What methods can be used to assess muscular strength? What is the relationship between strength & power? What p...

Methods of Resistance Training I Resistance Training: Science & Application EXSC216 Dr Jonathon Weakley Learning Outcomes What is muscular strength? What is muscular power What methods can be used to assess muscular strength? What is the relationship between strength & power? What physiological factors influence muscular strength Machine Weights Bodyweight Exercise Methods of Resistance Training 1. Variable Resistance Machines 2. Body Weight Exercises 3. Free Weights 4. Bands and Chains 5. Heavy Eccentric Training 6. Isometric Training 7. Plyometric Training Kinetics/kinematics, testing, levers Human Strength & Power Force – an influence that can cause an object to move Force = Mass x Acceleration Unit of force is a Newton (N) The application of force characterized by a rate of force production and can result in: ▫ Work being performed ▫ A velocity of movement ▫ A power output (W) Strength The ability to produce force (magnitude & direction) All movements depend upon strength Measured force or strength by: 1. Weight on the bar ▫ Defined as a % of 1RM 2. Isometric dynamometer ▫ Muscle gains tension without changing length 3. Isokinetic dynamometer ▫ The amount of force generated at a certain velocity Repetition Max Testing Direct assessment of strength 1 RM’s – usually concentric or SSC Advantage ▫ Very specific ▫ Inexpensive Disadvantage ▫ Does not give F-T curve (i.e. magnitude of peak force or RFD) – does not allow measurement of power ▫ Missed attempt near max creates excessive fatigue and reductions in load are missed as well  Isometric Testing Must select positions related to specific movements Joint angles producing highest force outputs By following these guidelines – correlations with dynamic measures are acceptable (for example): Mid-thigh isometric mid-thigh pull vs. Vertical jumps, Snatch, Clean Squat = 0.75 – 0.95 Stop & Jot… 1. Explain what force is 2. Explain what strength is and how it can be measured 3. What are the advantages of a 1RM test for assessing maximal strength? Power Power = Force x Velocity Velocity is the rate of change of position Power is more specific to athletic movements During the acceleration phase of sprinting, ground contact time is ~ 0.14s Not much time to exert force Athletic Movements Require different degrees of: ▫ Force ▫ Rate of force development ▫ Speed ▫ Power ▫ Endurance The importance of muscular strength in power development Strength & Power Trade-off Strength = the amount of force developed Power = the amount of force exerted at a given velocity Harris et al 2006 Strength & Power Relationships Stronger people can produce more power. Remember: Power = Force x Velocity Hori et al. 2008. Strength & Power Relationships Strength and power training (compared to just power training) develops power across the whole load-power and load-force continuum Training with only high velocity movements can improve one end of the force-velocity curve Training with both high force and velocity movements can improve both ends of the force- velocity curve Cormie et al. 2007. Influence of Strength on Power ES: 1.60 vs 0.95 ES: 1.59 vs 0.61 Stronger people tend to have LARGER and FASTER adaptations to power training. Good strength base is an important consideration for power development. Cormie et al. 2010 Influence of Strength on Power – Conclusions Power can be improved via strength training in weaker individuals Specific power training is required to maximise power potential Efficacy of power training increases with strength ▫ Motor unit recruitment STRENGTH = FOUNDATION OF POWER Stop & Jot… 1. Why is muscular power important for athletic performance 2. Is strength or power more important for athletic performance? Explain. LEVERS & TORQUE CURVES Levers Types of levers 1. First Class Lever ▫ Axis between force and resistance ▫ Example: Pair of scissors ▫ Body example: Triceps extending the elbow Levers Types of levers 2. Second Class Lever ▫ Resistance between axis and force ▫ Example: Wheelbarrow ▫ Body example: Push-up  Levers Types of levers 3. Third Class Lever ▫ Force between axis and resistance ▫ Example: Hitting a baseball ▫ Body example: Elbow Flexion/Biceps Curl  Levers Mechanical advantage will be reduced if: The distance of the resistance from the pivot point is long (long arms or legs) Or if the distance from the force to the pivot point is short (tendon insertion is close to pivot point). Levers The majority of body levers are THIRD CLASS Advantages Disadvantages Speed of movement Large torque created Range of motion Large forces required to move joint  29 Mechanical Advantage MR = 50 cm ME = 120 cm ME ÷ MR = 2.4 M R M E  32 Strength curve Dependent on the exercise, angle of pull, etc. McMaster et al (2009)  33 Force generating capacity increases as you move from bottom position to top (pos 4 to 1 in picture)  34 Force generating capacity decreases as you move from bottom position to top (pos 1 to 3 in picture)  35 Factors Impacting Torque Curve Shape & Amplitude Muscle cross-sectional area (CSA) Length of force & resistance arm Angle of pull of muscle on bone Muscle micro & macro architecture Fibre type Neural stimulus Force-velocity relationship Length-tension relationship Factors Influencing Strength CNS and neural control Muscle CSA Muscle fibre arrangement Muscle length Joint angle Contraction velocity Muscle Action Strength-to-mass ratio Neural Control Affects the number and type of motor units recruited Greater force is achieved by: ▫ Increasing the number of MU’s recruited ▫ Recruiting more high threshold MU’s ▫ Increasing the rate coding Muscle Cross-Sectional Area Moderate correlations between muscle CSA and strength This is due to more contractile apparatus being available to generate force Arrangement of the Fibres Arrangement of the Fibres Arrangement of sarcomeres in relation to the long axis of the muscle Pennation angle = angle at which the sarcomeres are in relation to line down middle ↑ pennation, ↑ force Muscles like Rectus Abdominis are non-pennate as their primary role is stabilisation Muscle Length Muscle length influences the overlap of actin and myosin filaments Muscle Length Joint Angle Torque must be generated to produce movements The joint angle influences the amount of torque that can be generated ▫ Muscle length ▫ Distance from the pivot Muscle Action Concentric muscle action ▫ Muscle gains tension and shortens Eccentric muscle action ▫ Muscle lengthens under tension ▫ Resists gravity to control movement ▫ Associated with muscle soreness Isometric muscle action ▫ Muscle gains tension but does not change length ▫ Trunk muscles Strength-to-Mass Ratio Increasing this ratio is important in a number of sports Sprinters need large amounts of muscle mass; BUT too much will compromise velocity ↑ body size = ↑ muscle volume & body mass Weight category sports need a comfortable weight and then become as strong as possible Sources of Resistance 1. Gravity ▫ An objects weight is the magnitude of gravity acting on it ▫ Always acts downwards 2. Inertia ▫ The resistance to movement ▫ Gravity only acts down, inertial forces act in any direction 3. Friction ▫ Resistive force between two objects ▫ More force is required to move a stationary object 4. Elasticity ▫ The greater the stretch in elastic, the greater the resistance Safety Proper exercise execution is imperative so that exercises are performed safely ▫ Reduce injury risk Load should never compromise technique Injury Prevalence – Hamill 1994 INJURIES PER 100 SPORT PARTICIPATION HOURS SCHOOL SOCCER 6.20 UK RUGBY 1.92 USA BASKETBALL 0.03 UK CROSS-COUNTRY 0.37 SQUASH 0.10 USA FOOTBALL 0.10 BADMINTON 0.05 USA GYMNASTICS 0.044 USA POWERLIFTING 0.0027 USA TENNIS 0.001 USA VOLLEYBALL 0.0013 WEIGHT TRAINING 0.0035 WEIGHTLIFTING 0.0017 Important Factors for Increasing Strength Training intensity (load lifted) Progressive overload Law of diminishing returns Type of muscle action Type of exercise Contraction Speed Machine Weights Pulley systems arranged to move adjustable weights against gravity Movement in a fixed plane Weight stack machines ▫ Adjustable stack of weights Plate loaded machines Machine Weights - Benefits Hypertrophy Strength? Improvements in power? Controlled Safety Spotters Injury rehab  Variable Resistance Machines Many machines utilise a ‘cam design’ Cam = rotating metal linkage Alters length of lever throughout ROM Aims to mimic human torque curve ▫ ↑ resistance during mechanical advantage ▫ ↓ resistance during mechanical disadvantage  65 Cam Levers What do you think are the benefits & limitations of this type of training?  66 Folland and Morris (2008) Dalleau et al (2010) Does it even work? Folland and Morris (2008) Machine Weights - Limitations Movement is limited Need a wide range of equipment Expensive Reduces stabilising muscle groups Isolated movements Improvements in power are limited to a few exercises Balance & coordination  68 Flywheels  69 Pneumatic Resistance Systems Resistance from compressed air Short deceleration phase What are the implications for training?  70 Pneumatic Resistance Systems  Force velocity curve of Pneumatic Several observations would be: ▫ 1) Ballistic training loading results in greater velocity in the later stages of the movement, the effects reduce with increasing load. ▫ 2) Pneumatic velocity appears greater from onset to termination of the movement across loads of 15 to 60% 1RM compared to free weight velocity. ▫ 3) Results in greater force outputs than free weights from 70 to 100% of displacement, due to less momentum to decelerate. Adaptations from training with pneumatic loading 8 weeks of training with Pneumatic or Free weights Pre-post changes in power for a 45% 1RM load were greater in the pneumatic trained group and there was greater power output from 10-90% of displacement. The free weight trained group only improved power output towards the end of the movement. Some evidence for early explosive power adaptation using pneumatic loading, especially if taken in tandem with the velocity curves. Body Weight Exercises Body weight is the resistance A wide range of exercises for increasing muscle strength and endurance Can vary the difficulty of these exercises to apply across the lifespan Basic motor skills Postural control Functional https://www.youtube.com/watch?v=POdzasJklxw https://www.youtube.com/watch?v=2WSgBXWVy_8 Questions 1. What is strength, how can it be measured? 2. Why is power important? 3. Which factors affect strength? 4. What is inertia 5. What are the limitations of machine weights? Suggested reading 1. Influence of Strength on Magnitude and Mechanisms of Adaptation to Power Training 2. Adaptations in Athletic Performance after Ballistic Power versus Strength Training 3. Training Principles for Power