4. strength, power, speed, agility Flashcards
definitions of strength, power, work, and atrophy
• Strength = ability to exert force ( = 1 RM = F in lbs)—F orce = Newtons (1 lb = 4.459 N)
• Power = the time of doing work… i.e. sit to stand ☺ → Power = Work/Time (in Watts)
• Work = Force x Distance (in Joules) → caloric expenditure {Energy}
*** atrophy w/i 24 hrs (↓ in protein synthesis). Adapts to both stress and a lack thereof.
strength reserve
• extra strength for an individual (beyond what is required to be independent) to leave room for loss (i.e in a pt post-op, etc.) before crossing the strength threshold into ‘dependent”
strength loss with age
• Strength loss = atrophy of muscle mass (loss of mm mass). w/ training = 5% decrease/10yrs after age 30 (w/o training = 10%)
power loss with age
- ↓rate of voluntary contraction.
- Type II fiber loss (fast twitch/higher force production)
o Average individual 50:50 fast to slow twitch… w/ aging, ↑ Type I vs. Type II (due to lack of use/stimulation)
functional importance of power
• ADL’s (getting out of chair, sweeping, take out trash)
o PREVENTION OF FALLS (catch yourself when falling) = primary need for strength, power, agility
o Lack of recovery from falls = major cause of death in elderly
Biomechanical factors
- Neural control
- Muscle CSA (proportional to strength)
- Muscle length
- strength to mass ratio
importance of neural control
• Neural control = recruitment (recruit low force mm fibers first – type I—and only recruit type II w/ high demand = size principle) + rate coding (speed of recruitment)
o With training, require high enough demand (stress) to stimulate type II fibers
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Importance of muscle length
-Cross-bridge optimization at resting length.
-muscle can generate greatest force at resting length, but ACTIVE lengthening disproves this
o
importance of strength to mass ratio
-Strength to mass ratio (all else being equal, smaller athletes stronger pound-for-pound)
o The bigger you are the more you have to move (w/ training, ~15%↑ in body mass, but only 10%↑ in force capacity = the ability to move/accelerate has DECREASED)
Sources of Resistance = gravity (free weights, weight-stack machines), friction (sled), fluid resistance (swimming), elasticity (therabands)
How can we increase power?
Power = Work / Time → can increase work, can decrease time, or BOTH
Training for Power = train both FORCE and VELOCITY
• Optimize rate of force development → RFD =change in force/change in time (heavy RT may NOT ↑ power)
plyometrics: purpose and models
- Activities that allow muscle to reach maximal force in shortest possible time
- Purpose: increase power of subsequent movements by using ELASTIC COMPONENTS of mm/tendon and the STRETCH REFLEX
- Functional mvmts depend on 1) muscle force production and 2) speed of muscular force production (POWER)
- Mechanical Model: elastic energy in musculotendinous components is increased w/ rapid stretch & then stored
• Neurophysiological Model: reflexive component of plyos comprised of muscle spindle activity → proprioceptive organs sensitive to the rate and magnitude of a stretch; reflexive stimulation ↑ force production w/ training
o Stretched beyond “normal” = contraction, then relaxation
o Relax = golgi tendon organ
plyometrics: training properties
• Training priorities: 1) basic fitness/preparedness. 2) proper mvmt technique (attention to volume). 3) manipulate the mvmt & intensity. 4) improve physiological capacity (aerobic & aerobic)
• Safety: pre-training eval, age, physical characteristics, technique, strength, speed, balance
• Equipment/facilities: landing surface (good = grass, rubber mat… bad = concrete, tile, wood), training area (SPACE), proper footwear (non-slip shoes), supervision
• Dynamic warm-up: ACTIVE vs. passive → marching, jogging, skipping, footwork, lunging
o Lower body: skips, jumps, box drills
o Upper body: throws (med ball), push ups
o Trunk: sit ups (med ball)
• Intensity: amount of stressed placed on involved muscle, connective tissues, and joints is controlled by type of drill performed = points of contact, speed, height of drill, body weight
o Progressions: jumps in place → standing jumps → multiple hops/jumps → bounds → box drills → depth jumps
- Frequency: 1-3x/wk
- Recovery: long work-to-rest ratio (1:5-1:10). Complete recovery btwn days – 24-48 hours (↑ demand, injury prevention)
- Volume: Beg) 80-10. Inter) 100-120. Adv) 120-140. QUALITY OVER QUANTITY.
Speed
• Speed: ability to achieve high velocity
Agility
Agility: multidirectional; ability to explosively brake; movement mechanics (requires more motor control)
• Running speed: stride length x stride frequency
o Elite sprinter – can increase stride length up to 49 yds (novice- max out at 27 yards). Similar difference in stride frequency
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Training agility concept
• Agility: involves greater emphasis on decelaration & reactive couple w/ accelearation than linear sprinting
o Closed/programmed = optimization of motor stereotype or technique (expected)
o Open/non-programmed = reaction & adaptation of a trained motor pattern to new or unforeseen situations (unexpected. Requires reaction)
• Agility: multidirectional; ability to explosively brake; movement mechanics (requires more motor control)
• Running speed: stride length x stride frequency
o Elite sprinter – can increase stride length up to 49 yds (novice- max out at 27 yards). Similar difference in stride frequency
• Agility: involves greater emphasis on decelaration & reactive couple w/ accelearation than linear sprinting
o Closed/programmed = optimization of motor stereotype or technique (expected)
o Open/non-programmed = reaction & adaptation of a trained motor pattern to new or unforeseen situations (unexpected. Requires reaction)
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