Types of Movement
• strength - greatest amount of force muscle can produce in
single effort
• power - rate of force generated
• endurance - ability to perform repeated submaximal
contractions
• flexion and extension
• abduction and adduction
• rotation
Types of Contraction
• isometric tension causes no change in length
– fibers shorten internally
• countered by antagonist
– ex: cutting horse poised
• concentric
– muscle shortens as it generates tension
– ex: flexor or extensor
• eccentric
– muscle lengthens as it generates tension
– used to resist force
– ex: flexor to control extensor and stabilize joint
• muscles develop greatest tension with eccentric contraction
– more soreness
• downhill work
• drop fences
• collected frame
Recruitment of Muscles
• affected by gait, speed, and duration of exercise
– change gait
• use different muscles
– change speed
• recruit more fibers for increases force
• controlled by nervous system
– fibers vary in their sensitivity to impulse
• walk
– mostly ST fibers
– only 10% of total fibers needed
• trot
– ST and FOG
– trot about 30 - 50 % fibers recruited
• canter
– more FG fibers recruited
• gallop (full out)
– 100 % fibers recruited
Effects of Conditioning
• changes structure and chemical composition of fiber
• twitch type does not change ( ST vs. FT )
• hypertrophy - muscle growth
– increases size and weight
• unfit - 42% of BW
• fit 50 % BW
– chemical effects
• increase enzyme levels
• increase amount of energy substrate stored
• affects vary with intensity, duration, and frequency of
regular exercise
• endurance training
– increase aerobic capacity
• increase in aerobic enzyme activity
– shift in preference of substrate use (fats)
• increase number of oxidative fibers (FG to FOG)
– rapid increase - first 2 months of training
• increase volume density of mitochondria
• increase capillary density
– decrease speed and power
• decrease fiber diameter
– slow adaptation - several months
– more efficient use of ATP with O2
• increase speed at which VLa4 occurs
• sprint training (anaerobic)
– increase power
• increase diameter of glycolytic fibers
– maximum force generated is proportional to cross
sectional area
– increase number actin and myosin myofibrils
– increase amount of connective tissue
– decrease aerobic capacity
• decrease number capillaries for fiber area
– improve buffering capacity in muscle fiber
• delay decrease of pH