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EXERCISE TRAINING TO IMPROVE MUSCLE STRENGTH AND ENDURANCE. What is the command chain of voluntary muscle contraction? Classification of muscle fibres How is the force regulated during voluntary contraction? What is muscle fatigue?. CORTICAL CONTROL AHC IN SPINAL CORD MOTONEURON
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What is the command chain of voluntary muscle contraction? • Classification of muscle fibres • How is the force regulated during voluntary contraction? • What is muscle fatigue?
CORTICAL CONTROL AHC IN SPINAL CORD MOTONEURON AXON GROUPS OF MUSCLE FIBRE NMJ MUAP MUAP E-C COUPLING MUSCLE CONTRACTION FORCE GENERATION Initiation of voluntary movement
MUSCLE FATIGUE • Various definition • “Any reduction in the force-generating capacity of total neuro-muscular system, regardless of the force required in any given situation” Bigland-Ritchie (1984) • Site: Central and Peripheral
CORTICAL CONTROL AHC IN SPINAL CORD MOTONEURON AXON GROUPS OF MUSCLE FIBRE NMJ MUAP MUAP E-C COUPLING MUSCLE CONTRACTION FORCE GENERATION Initiation of voluntary movement
STRENGTH TRAINING • GENERATION OF MUSCLE FORCE • Recruitment order • Firing Frequency
MUSCLE MECHANICS • Muscle length • Force-length relationship • Rate of change in muscle length • Force-velocity relationship Therefore, muscle tension depends on muscle length and velocity
PRINCIPLES OF EXERCISE TRAINING • Overload • Progression • Specificity • Adaptation • Reversibility • Individualisation
OVERLOAD PRINCIPLE • To increase the size or functional ability, muscle fibres must be taxed toward their present capacity to respond • it is not the absolute force that determines the quantity of the stimulus but rather the size of force relative to the maximum
SPECIFICITY PRINCIPLE • Training adaptations are specific to the cells and their structural and functional elements that are overloaded. • Strength vs Endurance
STRENGTH TRAINING • ISOMETRIC • ISOTONIC • ISOKINETIC • ES
ISOMETRIC TRAINING • Consider threshold point, intensity levels and systematisation of the program • 40-50% of IMVC, 5-8 rep. 4-6 s. (untrained individuals) • 80-100%, 5-10s and 2-5 rep. (elite athlete)
DISADVANTAGES • angle specific (10 degree) • heart rate and BP
DYNAMIC • Concentric Vs Eccentric • Eccentric - more force generation Colliander & Tesch (1990) • Knee ext. training programme • mode 3/7 x 12/52 • Concentric =18% improvement • Concentric + eccentric = 36% improvement
Training mode • Isokinetic • Accommodating resistance • Speed specific • Open chain
NMES • Rationale • Neural insufficiency - the force exerted during a MVC can be increased with single electric shocks
Kots protocol (Russian technique) • Freq: 50Hz • Repetition: 10 • on / off cycle: 10s: 50s • improvement 1.6% per session
Lower force requirement • Laughman et al (1983) • isometric vs NMES • similar improvement (18 vs 22%) • training intensities: 78 vs 33%
LOADING PRINCIPLE • PRE • DeLorme (DeLorme 1945) • 50% 10RM, 75% 10RM, 100% 10RM • Oxford Technique (Zinovieff 1951) • Reverse of Delorme • Light to heavy system • 10 RM x1, 8 RM x1, 6 RM x1 • Circuit training
ADAPTATION TO EXERCISE • Plasticity of muscle • Neuromuscular Adaptation • Remember: Torque is the interaction of the neural (motor unit recruitment and discharge rate, mechanical (moment arm) and Muscular (length and cross-sectional area)
NEURAL ADAPTATIONS • Precedes muscular adaptations • reflects from changes in EMG
Suggested reading • Malone, T.R., McPoil, T., and Nitz, A.J., (1997) Orthopaedic and sports physical therapy, 3rd edition. Mosby. Chapter 9