CIV Fitness/S&C Steven Tikkanen – F129 1 Sutherland College Health & Recreation Semester Version 1

MUSCLE PHYSIOLOGY & NEUROMUSCULAR ANATOMY AND ADAPTATIONS TO CONDITIONING ESSENTIALS OF STRENGTH TRAINING AND CONDITIONING CHAPTERS 1 & 2

FIBRE TYPES Type I (or slow twitch) Type II (or fast twitch) Type I Resist fatigue by having large numbers of mitochondria High aerobic enzyme activity Dense capillary concentration

FIBRE TYPES Type II Type IIb Muscle fibre fatigues rapidly Relatively few mitochondria Low aerobic enzyme activity Few capillaries Type IIa Has some of the fatigue-resistant qualities of Type I muscle fibres More mitochondria Greater aerobic enzyme activity Greater capillary density Compared to Type IIb muscle fibres

TYPES OF MUSCLE ACTION Concentric muscle actions Occur when the total tension developed in all cross-bridges of a muscle is sufficient to overcome any resistance to shortening. Isometric muscle actions Occur when the tension in the cross-bridges equals the resistance to shortening. The muscle length remains relatively constant.

TYPES OF MUSCLE ACTION Eccentric muscle actions Occur when the tension developed in the cross-bridges is less than the external resistance The muscle lengthens despite contact between the myosin cross- bridge heads and the actin filaments

ACTIVATION OF MUSCLES Motor unit Is a motor neuron and all of the muscle fibres that it innervates. This is the basic functional entity of muscular activity.

ACTIVATION OF MUSCLES Acetylcholine Is the neurotransmitter released at the pre-synaptic terminal that causes excitation of the sarcolemma. Not the action potential (electric current)

NEUROMUSCULAR ANATOMY AND ADAPTATIONS TO CONDITIONING Neuromuscular anatomy and physiology All-or-none principle – same as firing a gun. Once a sufficient amount of pressure is placed on the trigger, the gun fires; however, squeezing the trigger harder will not cause the bullet to go faster. A stronger stimulus does not cause a stronger contraction. Twitch – is an action potential travelling along a motor neuron results in a short period of activation of the muscle fibres within the motor unit.

NEUROMUSCULAR ANATOMY AND ADAPTATIONS TO CONDITIONING Recruitment If the activity requires near-maximal performance, such as a power clean. Most motor units are called into play. With Type IIb making the more significant contribution. Complete activation of the available motor neuron pool is probably not possible in un-trained people.

NEUROMUSCULAR ANATOMY AND ADAPTATIONS TO CONDITIONING Proprioception Proprioceptors – are located in joints, muscles and tendons. Kinaesthetic sense – is the information sent to the brain consciously or unconsciously by the proprioceptors, to give conscious appreciation of the body in three-dimensional space. Muscle spindles – intrafusal fibre sense stretch and send information to CNS, the motor neuron sends information back for the extrafusal fibres to contract, to take away the stretch. Knee jerk test.

NEUROMUSCULAR ANATOMY AND ADAPTATIONS TO CONDITIONING Golgi tendon organs – GTO feels stretch if the stretch is to great then the GTO will switch off the muscle under stretch. Neuromuscular adaptations to exercise Hypertrophy – increase in muscle cross sectional area (CSA). It has been found that fast twitch muscles increase in size much more than slow twitch muscles. Therefore it has been suggested that fast twitch athletes will have a greater CSA.

NEUROMUSCULAR ANATOMY AND ADAPTATIONS TO CONDITIONING Hypertrophy – cont. – Time – it can take up to 6-8 weeks to see any hypertrophy in muscle. As the first few weeks strength will come from neural adaptations. Both intramuscular and intermuscular coordination improves. Therefore less muscle is needed to perform work, therefore must increase intensity.

AEROBIC ENDURANCE TRAINING Aerobic endurance training increases aerobic power, it does not enhance muscle strength or size. In fact, intense aerobic endurance training can actually compromise the benefits of resistance training.