6. Skeletal Muscle Adaptations to Resistance Training Flashcards
at what age threshold do we usually see skeletal muscle changes impact functional capacity and frailty?
- describe the continuum of skeletal muscle during aging
- older adults who stay physically active have greater (3) than inactive older adults
- 80 yo! (can start at 70)
a) older frail –> sedentary, inactive –> muscle atrophy, sarcopenia
b) older robust –> lightly to moderately active, might not meet guidelines but does some PA
c) masters athlete –> very physically active
- greater muscle strength, power and physical performance
what are muscular adaptations/benefits to resistance training in older adults? (8)
- increase skeletal muscle mass and fat-free mass (leads to increase REE)
- decrease fat infiltration in skeletal muscle (important for muscle quality)
- increase muscle strength and power
- increase motor unit number and firing rates (neuromuscular aspect)
- increase skeletal muscle oxidative enzyme levels (metabolic)
- increase skeletal muscle capillarization (allow O2 transport)
- increase mitochondrial content and function
- increase resting energy expenditure
can resistance training improve muscle MASS? (describe 3 points)
1) regular PA can prevent low muscle mass –> reducing likelihood of becoming sarcopenic in later life
*recall: sarcopenia = low muscle mass/area, low muscle strength/power, low physical performance
2) losses of fat-free mass can be 9 times greater in inactive vs physically active older adults! (1-2% per year loss if no PA, vs 0.4% loss ish/10 years for RT vs 1.6% loss/10 years fo aerobic training)
3) MA: 20.5 weeks of RT, men and women aged 50-83 yo experiences a significant gain of 1.1 kg in FFM –> clinically relevant!
- define muscle hypertrophy
- muscle hypertrophy following regular resistance training (__-___ days/weeks) in older adults can be substantial, ranging from ___-_____ after 9-52 weeks
- do younger and older men report similar gains in muscle size after same RT program?
- is sarcopenia of a biological/primary aging or disuse/inactivity origin?
- increase muscle area and mass
- 2-3 d/week –> 10-62%
- both have similar gains!
- independent of chronic disease, inactivity really drives the decrease in muscle mass as one ages
RESISTANCE TRAINING TO IMPROVE MUSCLE SIZE:
1) describe high-intensity resistance training –> results? (on muscle area and strength)
2) what happens to muscle fiber types after high-intensity RT?
3) does high-intensity RT lead to more robust hypertrophy in young or older adults with sarcopenia?
1) 2-3 d/wk at >75% 1RM –> large improvements in lower-body muscle size after 3-months high intensity RT –> increase muscle area and strength! (strength improvements can be partly attributed to increased muscle CSA and volume, but also neuromuscular factors!)
2) after 16 wks (2 days/wk, 3 x 6-8 reps, 86-90% 1RM) –> all fiber types became larger in older adults compared to untrained controls + shift from type IIB to IIA type profile (decrease in IIB, increase in IIA and I)
3) 3 days/wk, 3 x 8-12 reps at 75-85% 1RM –> more robust hypertrophy in young (20-35 yo) vs older adults (60-75)
- can older adults substantially increase their muscle strength after RT?
- influence of age on capacity to increase muscle strength after RT is affected by (4)
- yes! reported increases range from <25% to >100%!!
- sex/gender
- duration of training intervention
- type of exercise training
- specific muscle groups examined
- what type of RT can lead to significant gains in lower-body muscle strength and size, even in frail adults? –> leads to what?
- vs what are the FITT variables to improve muscle strength? (from the meta-analysis)
- high intensity RT! –> 3x/wk, 3 x 8 reps at 80% 1RM for 8 weeks –> results in increased 1RM + increased muscle mass
F: 2-3x per week
I: 40-85% of 1RM, 2 x 10 reps
T: duration, not indicated, length: 18 weeks
T: leg press, chest press, knee extension, latissimus dorsi pull-down, etc.
- majority of strength gains in older adults is due to what? after short-to-medium term training (8-20 wks in length)
- RT is associated with an increased (3) related to the first answer
- neural adaptations!
- increased rate of force development, EMG amplitude and maximal voluntary contraction!
*even if older adults have lower peaks, they can still improve!
how to estimate 1RM in older adults?
- not super safe to actually do a 1RM test
1) 5min dynamic warm-up
2) light weight to perform 10 reps with correct technique
3) add weight a match a load that could be completed for a minimum of 5 reps but less than 10
*a maximum of 3 sets of incremental weight is to be added per session when predicting 1RM (+5-10 lbs for upper body, + 10-20 lbs for lower body) –> if not, wait 48h until attempting the same protocol
4) use formula: 1RM = weight / (%1RM value from table / 100)
1; 100
2; 95
3; 93
4; 90
5; 87
6; 85
7; 83
8; 80
9; 77
10; 75
- can older adults have improvements in muscle POWER after RT? what about with traditional RT?
- why is muscle power important?
- substantial improvements in muscle power CAN be demonstrated
BUT muscle power may not be as responsive to traditional resistance training –> due to lack of specificity and bc muscle contraction velocity is too slow - existing evidence suggests that muscle power is more strongly associated with physical performance than muscle strength
- describe high-velocity RT
- maximal contraction velocity occurs at ____% 1RM, whereas peak power occurs at ____% 1RM
- what should older adults aim for?
- involves performing the concentric muscle contraction as rapidly as possible, while eccentric phase is performed in a slow, controlled manner
- 40% 1RM (and decreases as %1RM increases) –> peak power at 70% 1RM (slowly increase from 40% to 70% then drops low at 90%)
*although peak power occurs at lower velocity, the independent effect of velocity is meaningful bc it has been associated with better physical function in older adults
GOAL: high power and high velocity! around 40-60% 1RM
- what type of training may be superior to enhance lower extremity muscle power in middle-aged and older adults than traditional RT?
- high or moderate or low training volume has bigger effect?
VS another study focusing on elderly (65-94 yo) with mobility limitations: what type of RT was better? describe FITT ish
VS a meta-analysis: power training vs traditional strength training in older adults –> which yielded higher physical performance/functional outcomes?
- high-velocity/power resistance training!
- moderate has stronger effect vs low or high training volume
- high velocity resistance training and traditional slow-velocity RT (3x/wk, 3 sets of leg-exercises at 70% 1RM for 12 weeks) yielded SIMILAR increases in lower-extremity power over 12 weeks
- power training!
- describe muscle endurance
- how to measure?
- is it well maintained as one ages? explain
- ability of a specific muscle group to execute a repeated number of contractions over a time period sufficient to induce muscular fatigue
- examining the number of times or length of time (typically to exhaustion) that the individual can successfully lift a weight while maintaining proper form
- Muscle endurance is better maintained with aging than muscle strength and power –> more gradual and modest loss of muscular endurance with aging BC type 1 muscle fibers are maintained with age! better preserved
- which 3 types of training protocols have been shown to produce improvements (___-____%) in muscle endurance? –> 3 effects ish
- what are 5 mechanisms underlying increased muscle endurance in response to RT training?
- aerobic, resistance and interval training protocols! 34-200% improvements!
- increased aerobic capacity, fatigue resistance and muscle endurance of mitochondria!
- decreased motor-unit activation required to complete submaximal task
- decreased coactivation of antagonistic muscles
- increased high-energy phosphate availability (ATP, PCr)
Shift in myosin heavy chain isoforms (IIx –> IIa fiber types) - increased mitochondrial density and oxidative capacity (increased oxidative enzyme levels)
describe 2 ways types of RT to improve muscle endurance ish
- short-term endurance related activities (30sec - 2min)
- moderate weight loads (40-60% 1RM) at high number of reps or exact time length
- can help train posture! - long-term endurance (>2min):
- running, swimming, cycling
- low-to-moderate weight loads (30-40% 1RM) at high number of reps or sport-specific activities recruiting those muscles for over 2 min
what are the FITT variables for RT recommendations from ACSM and AHA?
FREQUENCY: at least 2days/wk, per muscle group
INTENSITY: btw moderate (RPE 5-6) and vigorous (RPE 7-8) intensity
- strength: 70-85% 1RM
- power: 40-60% 1RM
TYPE: progressive weight training (free weights or machine-based exercise) OR weight-bering calisthenics
- 8-10 exercises involving major muscle groups
- 1-3 sets of 8-12 or 10-15 reps
TIME: no specific duration
- is more frequent RT better?
- dose-response effects exist for muscle strength (1RM) when predominantly using weight-training machines, but not leg lean mass –> 3days/wk has bigger increase in 1RM load (compared to 2x, 1x and 0x / wk)
- beneficial functional improvements (ie time up and go) can be achieved through low frequency training (similar benefits for all 3 groups: 1x, 2x, 3x)
bottom line: 2/wk is the rec –> than look at tolerance and benefits from doing more and risks
is low-intensity resistance training effective?
- Progressive RT has been shown to be an effective method for enhancing muscle strength, power, and physical performance
- Higher intensity > lower intensity resistance training for improving maximal muscle STRENGTH, but not power and physical performance (ie stair climbing, walking speed, timed up and go), in older adults
is concurrent training good/bad for you? explain
- 2 studies results
- bottom line?
- similar max isometric leg press (muscle strength) btw strength and concurrent groups
BUT strength group had much higher cross-sectional area of muscle fibers (muscle hypertrophy) –> so concurrent exercise training may interfere with muscle hypertrophy in untrained middle-aged and older men, despite similar strength gains
*might have interference effect where aerobic training interferes with muscle growth! mostly by altering muscle protein synthesis
HOWEVER, another study showed that concurrent training (aerobic and resistance) is as/more effective, compared to only aerobic or resistance, for increasing several strength and physical performance outcomes (gait speed, sit-to-stand, hand grip strength)
bottom-line: no less benefits if you do both aerobic and resistance (concurrent)
do RT-induced changes differ by sex?
- changes in ABSOLUTE upper-body and lower-body strength were greater in older males than females
- BUT changes in upper-body and lower-body strength were greater in older females than males
- bottom-line: not much difference btw male and females –> depends on each person’s tolerance
You work for the local YMCA and have been asked to design an exercise class to increase muscle strength and power in older adults. In small groups, you will discuss the following questions and share your exercise plan with the rest of the class.
What types of exercises would you pick, for how often, and at what intensity should they be performed?
STRENGTH:
F: 2-3x/wk (won’t have further benefits if >3)
I: >70% 1RM for bigger effects. start at RPE 5-6 –> increase to 7
T: shoulder press, chest press, squats, bicep curls…
T: 1-2 sets, 8-12 reps (hypertrophy) OR 1-2 sets, 5-8 reps (strength)
POWER:
F: 2/week
I: 40-60% 1RM
T: high velocity, explosive exercises! ie explosive leg press, fast concentric + slow eccentric, move functionally (stair climbing, vertical jump), bands…
T: 1-2 sets, 8-12 reps –> but more focus on intensity and type of exercise
