Strength, Power, and Anaerobic Capacity PDF

Strength, Power and Anaerobic Capacity MEDI221_Lecture 15  Objectives: Revise: Strength Torque-angle relationship Force-velocity relationship Why strength is important and why it is measured Define Power Power-velocity relationship Training for streng...

Strength, Power and Anaerobic Capacity MEDI221_Lecture 15  Objectives: Revise: Strength Torque-angle relationship Force-velocity relationship Why strength is important and why it is measured Define Power Power-velocity relationship Training for strength and power Strength in elderly How strong or powerful are these individuals? Your Turn: 1. Which is more powerful? 2. Why are they stronger? 9/3/21 Strength and its importance Muscular strength Generate force Force = m.a Why is it important? Human movement ADL e.g. walking Athletic performance ­ Force = ­ Power 4  INTRINSIC MUSCLE PROPRIOCEPTIVE PSYCHOLOGICAL FACTORS PROPERTIES INFORMATION COMPLIANCE & STIFFNESS MOTOR UNIT OF MTU -Recruitment -Firing TENDON -Synchronisation STRUCTURE MUSCULAR CNS RECENT +/- input MOVEMENT FORCE HISTORY NEURAL & REFLEX CIRCUITS POST-ACTIVATION POTENTIATION MUSCLE TEMPERATURE PHOSPHOCREATINE RESYNTHESIS/DEPLETION STRUCTURAL PROPERTIES OF MUSCLE 5 Why Measure Strength? Amount of force Implications Muscular function Rehabilitation Functional capacity Injury prevention Identify: Weak muscle groups 6 Isokinetic dynamometry (ID) 7 Torque-angle relationship of the knee extensors 8 Force-velocity relationship of human elbow flexors and extensors Power-velocity relationship - concentric Your Turn: 3. Why can you produce more force with eccentric contrac=ons? Specificity of training Trained at both A and B below Trained high forces Trained High + low velocity velocities + low force 12 Resistance Training á strength by two mechanisms Neural Strength/Power Training 100 Hypertrophic Contribution to á strength (%) 80 Muscular Neural 60 Adaptation Adaptation 40 - Propor%on of - Recruitment muscle fibre types. - Synchronisation 20 - Enzyme ac%vity - Firing frequency - Hypertrophy 0 0 2 4 6 8 Training duration (wks) Different time course for each mechanism! 13 Training Regimes and Their Basis– it’s not B&W Research pertaining to how we should prescribe resistance training is conflicting: Does Resistance Training have to hurt? (esp. reps to failure) For strength gains, No. (Folland et al., 2002) (At least if not already well trained) Does it matter how many sets? (1, 2 or 3?) Not particularly, esp. early in training! (Hass et al., 2000) Does it matter how much load (i.e., %1RM) May not be as important as advocated in guidelines (Mitchell et al., 2012) Training strength: Achieving gain without pain Folland et al., (Oct 2002), Br J Sports Med, 36: 370-373 Objective: What is role of fatigue and metabolite accumulation in strength gains? 23 adults (8 women) assigned to 3 sessions/week of either: High fatigue (4 sets of 10 reps @73%1RM, 30 s btwn sets) = max metabolic stress Low fatigue (40 reps @73%1RM, 30 s btwn reps) = min metabolic stress. Full ROM knee extension, both legs. Test: isometric @90°, and torque*velocity*length Concluded: nFatigue & metabolite accumulation not critical stimuli for strength gain? nResistance Training can be effective without severe discomfort and acute physical effort of fatiguing contractions. Training strength: Achieving gain without pain Hass et al. Med Sci Sports Med (2000) Objective: Does increasing sets from 1 to 3 improve strength or strength endurance? 42 adults, RT for 1 year, assigned to 1 or 3 sets/session for each exercise 9/3/21 Concluded: No benefit of additional sets for any outcome variable. Training strength: Achieving gain without pain Objective: Does pattern of load affect signalling mechanisms or hypertrophy outcome? Mitchell et al. J Appl Physiol (2012) Resistance exercise load does not determine training-mediated hypertrophic gains in young men Concluded: lower load and heavy load lifted to failure = similar hypertrophy Training techniques – Plyometrics (~bounding) High Explosive Exercise - Stretch-Shortening Cycle á Ability to tolerate high-stretch loads á muscle power output Stored elastic energy Stretch reflex Train speed & power (high velocity & RFD) 9/3/21  4. What are you training with plyometrics? Your Turn: 5. Will plyometric training improve IRM strength? i.e., for weight lifting? 9/3/21 Research: Plyometrics Vertical jump performance Squat Jump 8.1% Counter Movement Jump 9.9% Depth Jump 13.4% Sprinting 10m 2.2% 12m 2.1% 20m 1.5% 30m 1.3% Markovic, G. & Mikulic, P. (2010). Neuro-musculoskeletal and performance adaptations to lower-extremity plyometric training. Sport Medicine. 40(10), 859- 895. Principles of Anaerobic fitness Two energy systems contribute heavily. “Anaerobic” fitness involves: Strength Power & speed Speed-endurance Rapid recovery High specificity Training the energy systems. Remember: Power of each system by stressing rate of ATP supply Capacity of each system by stressing duration of ATP supply (at highest rate).  Max-effort power is higher & be