EXPH 365 1st Edition Lecture 8Current LectureMuscle strength/force/tension- Factors:o Overlapo Cross sectional areao Speed of contraction o Fiber typeo Number of fibers and filaments that are activated- Length/tension relationshipo Amount of actin and myosin overlapo Isometric testing (cross bridges form but there is not even strength to move the tension) varies by angle of jointo Shorter lengths Increased space  Not as many binding sites Thin filaments overlap Can’t reach the because the fluid from the sarcoplasmic reticulum bulges up and pushes the actin away from the myosino Longer lengths Not as much overlap of filaments- Actin/myosin overlapo Resting length- can change due to lifestyle o Muscle optimal length – max force is achieved/max overlapo The more overlap of filaments the more force that can be generated- Cross sectional areao Muscles increases size by increasing filaments- hypertrophyo Getting stronger by adding myofilaments (actin/myosin) in a given fiber o Hyperplasia is increase in cell number (not really in humans once infancy is over)o Hypertrophy is just the cells getting bigger (happens in people)- Speed of contractiono Inverse relationshipo Faster muscle contracts, it cannot produce as much forceo Cycling rate of cross bridges- Force velocity relationshipo At max velocity of contraction the load is zeroo Heavier weight, slower contraction- Fiber typeso Type 1- slow twitcho Type 2- fast twitch 2a and 2xo Differ in metabolism, nerve stimulation and sizeo Perform differently based on twitch speed, peak force, and endurance- Type 1o Best endurance (oxidative metabolism)o Speed of contraction is slowo Force is lowo Very low fatigueo Small nerves for nerve impulse- 2ao Metabolism use both oxidative and glycolytico Fast speed of contractiono Moderated forceo Moderate Fatigueo Moderate nerve impulse with moderate sized nerveso “Switch hitters” because they contain characteristics of both fiber typedepending on training - 2xo Metabolism is all glycolytico Very bad enduranceo High forceo Very fatigueo Large nerveso Power and strength fibero Proteins that surround myosin head are different - Both fibers present in all muscles o Genetics influence o Sprinters higher % fast twitch, marathon runners higher % slow twitcho All muscles can hypertrophy  Intermediate increase the most - Order of activationo For all activities activation is the sameo 4-6 weeks to see increase in muscle size o Nervous system sends signal to activate the smallest nerves first and then on to the bigger nerveso Feedback from receptors in the muscle/brain tell the nerve if it needs to increase its signal o Type 1 gets activated first and so