Transcript Calcium Signaling - Georgia Institute of Technology

Training
• Describe the differences between human
exercise and animal models of muscle
plasticity
• Training-induced neural plasticity
• Training strategies for modulating muscle
recruitment
Training programs (cardio)
• P90X/Insanity (12 weeks)
–
–
–
–
–
30-60 min/day, continuous
Progressive (a little)
low load: no failure
70-80% HRmax; 50-80% VO2max
Rotating muscle groups
• HIIT (High Intensity Interval)
– 30 min / day, continuous
– 40-50% VO2max with 30-60s anaerobic intervals
Training programs (strength)
• HIT (High Intensity)
– 30-60 min / 2-3 day, short rests
– 10-15 RM, recalibrated regularly, Consistent routine
• HST (Hypertrophy specific)
–
–
–
–
60-90 min/ 2-3 day, intervals
Progressive
Max-load (2x15, 12, 10, 8, 5-rep max)
Consistent routine, emphasis on form
• Powerlift
–
–
–
–
60-90 min/day, intervals
Progressive
High load (4x15, 12, 10, 8, 5-RM)
Rotating muscle groups , emphasis on completion
Training programs (research)
• Endurance
– 30-60 min/day
– 60-80% VO2max
– Consistent routine (usu. cycling/running)
• Strength
– 10-30 min /2-3 days
– Single muscle group
– 2-4 sets of 6-10 RM
• 8-16 weeks
Human variability
• Single greatest challenge to human research
– Heterogenetic
– Diet & activity variations
– Drug/bioactive chemical
variations
• Sample size
– n=5resolution ~2 S.D.
– n=8 ~ 1.5 S.D.
– N=12  ~1.2 S.D.
Satellite cells pre/post training split
by magnitude of hypertrophy
(Petrella & al., 2007)
Recruitment
• Voluntary
– “Pacing” ie: projecting future activity requirement
– Regulatory feedback
• Recurrent/Renshaw inhibition
• GTO/force dependent inhibition
• Central fatigue
– Skill
• Involuntary
– Intensity
– Frequency
– Synchrony
Power-endurance curve, Morton
& Hodgson, 1996
Recruitment during endurance ex
• Pacing: activity increases at end
• Temperature: central fatigue/stress reduces
activity
15 °C
35 ° C
15 °C
35 ° C
Activation
restricted to
~30% MVC
Tucker & al., 2004
Training specificity
• Kanchisa & Miyashita (1983)
• Isokinetic training at
several speeds, 8 wk
• Performance increases
only near training speed
Training Specificity
• Kitai & Sale (1989)
– Isometric: 2x 10 “max”
– 6 weeks
• Strength gain only at
training angle
Training Specificity
• Aagard & al., 1996
– Soccer players
– Isokinetic @8 RM, 24 RM
– “Loaded-kick” 16RM @ 0-400 deg/s
• High resistance improve isokinetic strength
• No changes in kicking performance
• “HST” vs “Power” training
– Form over performance
– Break in form may allow ‘testing’ of control
pathways
Recruitment during controlled task
Mechanical balance
may limit the
contribution of some
muscles. Esp skilled
motions
fMRI of arm before & after maximal curl exercise (Adams & al., 1992)
fMRI of calf before and after plantarflexion exercise (Yanagisaw & al., 2003)
Electrical stimulation
• Animal
– Cuff or hook electrodes on the nerve
– Often anesthetized
• Human
– Surface electrodes
– Awake subjects
– Pain threshold
fMRI of electrically stimulated quadriceps
at tolerance limit ~50% activitation
Completeness of MVC
• MVC: maximal voluntary
contraction
• Interpolated twitch
– Add a single electrical pulse during
Tension rise due to
MVC
synchronous, max activation
Tension fall due to GTO,
spindle feedback; antidromic
collision
Effect of an electrical pulse during
voluntary activation (Belanger &
McComas, 1981)
Effect of an ‘extra’ impulse during an
electrically evoked train (Belanger &
McComas, 1981)
Completeness of MVC
• Sensitive to posture
• Sensitive to motion
• Different among
muscles
• Confused by synergists
Voluntary force (%MVC)
Endurance and interval
• Burgomaster & al 2007
– 50 min continuous 60% VO2
cycling
– 5x30s max anaerobic in 30 min
• Equivalent metabolic gains
• Similar signaling
– PGC-1a
– CS
– etc
Long/slow contractions increase recruitment
• MU fatigue reduces force
capacity
• Fatigued units
replaced by new
• Strategy for improving
recruitment
DeLuca & al., 1996
Garland & al., 1994
Sets and Reps
• Berger (1962-1968)
• 1-3 sets; 2-10 reps, 20 students/group
• 12 weeks, max bench press
124±21 
I
II
III
2
149±21
146±18
154±24
6
156±28
153±23
161±21
10
151±18
156±27
153±24
Intensity-protein synthesis
• Kumar & al, 2009
– 40-90% 1-RM
– Reps set to match force*time
– Protein synthesis 1-2 hr post
• Can’t resolve anything
– n=5
– Trend is consistent
with intuition
Sets and reps
• Stuart Philips’ lab (2010-2012)
• Vary sets and load (reps to failure)
mTOR/ERK
siganling consistent
with this
– Highest protein synthesis at lowest load
– No difference in performance or hypertrophy
Protein Synthesis
Muscle Size
4x5 RM
4x14 @24 RM
4x24 @24 RM
Burd & al., 2010
Mitchell & al., 2012
Detraining
• Bickel & al., 2011
– 16 weeks Resistance training
• 3x10-RM
• 3/week
– 16 weeks Detraining
• No exercise
• 1x10-RM, 1/week (1/9)
• 3x10-RM, 1/week (1/3)
• Age-dependent loss
– 1/3 volume maintains young
Summary
• Neural control is a big part of “strength”
– Coordination of multiple muscles
– Complete recruitment of individual muscles
• Manipulating the nervous system is a big part
of training
– Practice to improve control
– Fatigue to improve recruitment
• Lessons from animal models are hard to
translate
– Forcehypertrophy
– Chronic activityendurance