Transcript Running Clinic - Lactate Threshold

2012 Northern California All-Sports Clinic
The Causes of Fatigue and
How to Combat Them
© Jason Karp, Ph.D.
RunCoachJason.com
Founder/Coach, REVO2LT Running TeamTM
Freelance writer & author
2011 IDEA Personal Trainer of the Year
What is Fatigue?
The inability to maintain or repeat
a given level of muscle force
production, resulting in an acute
impairment of performance.
Causes of Fatigue
• inadequate ATP resynthesis via aerobic
metabolism
•
•
•
•
acidosis & accumulation of metabolites
CNS/neuromuscular?
glycogen depletion/hypoglycemia
dehydration
• causes decrease in plasma volume of blood, decreasing
stroke volume & cardiac output
• muscle fiber damage
• results in fewer functioning actin-myosin cross-bridges
• hyperthermia
• Decreases blood flow to active muscles
• reduces mitochondrial respiration & ATP regeneration
Inadequate ATP Resynthesis
Improve cardiac performance to
increase blood flow to muscles and
improve characteristics of aerobic
metabolism so that reliance on O2independent ATP regeneration is
delayed.
The 3 Players of Distance Running
Running Economy
O2 cost of maintaining a given pace
VO2 max
maximum volume of O2 consumed per
minute
L actate Threshold
speed above which lactate accumulates
& acidosis occurs
VO2max
• Maximum volume of oxygen muscles consume per
minute (maximum rate of oxygen consumption).
• Most often measured variable in exercise physiology.
• Expressed as liters/min or ml/kg/min.
• Although a high VO2max alone is not enough to attain
elite-level performance, it gains one access into the
club. An athlete simply cannot attain a high level of
performance without a high VO2max.
• Largely genetically determined.
• Males have higher VO2max than females, primarily
due to differences in cardiac output and blood
hemoglobin concentration.
What Determines VO2max?
• Cardiac output & blood flow
(central factors)
• Cardiac output dependent on:
• stroke volume
• heart rate
• Stroke volume determined by:
• venous return
• heart contractility
• amount of pressure in left ventricle (preload)
• amount of pressure in aorta (afterload)
• size of left ventricle
What Determines VO2max?
• Blood flow dependent on:
• redistribution of blood away from other tissues & to
active muscles
• resistance of blood flow through blood vessels
• adequate dilation of blood vessels, which depends on
interplay between sympathetic & parasympathetic
nervous systems & associated hormones
• O2 transport capacity of blood, which is determined by
red blood cell volume & amount of hemoglobin, which
transports O2 in blood
• amount of myoglobin, which transports O2 in muscles
• density & volume of capillaries that perfuse muscle fibers,
which determines time available for diffusion into muscle
mitochondria
Transporting oxygen from the heart to the muscles is a complicated matter!
What Determines VO2max?
• Extraction & use of O2 by muscles
(peripheral factors)
• Dependent on mitochondrial & capillary
volumes & enzyme activity.
• Reflected by difference in amount of O2
going to muscles through arterial
circulation & amount coming out through
venous circulation (a-v O2 difference).
• a-v O2 difference determined by convection
of O2 through muscle capillaries and its
diffusion from capillaries to mitochondria.
Fick Equation
VO2 = SV x HR x (a-v O2 difference)
VO2 = CO x (a-v O2 difference)
Central factors
Peripheral factors
VO2max occurs when SV, HR (and therefore cardiac
output), & a-v O2 difference are at maximum.
Central vs. Peripheral
Limitation?
• Unfit people seem to be equally limited by central & peripheral
factors (they lack both high blood flow & abundant metabolic
machinery)
• Highly trained endurance athletes are more centrally limited.
• Training causes a shift of limitation on sliding scale—the more fit
you become, the more you move away from a metabolic
limitation to VO2max and the closer you move to an O2 supply
limitation.
• Progressive increases in mileage improve VO2max by increasing
muscles’ metabolic capacity. Once you have achieved a high
level of mileage, intensity of training becomes more important
to increase cardiac factors responsible for maximizing O2 supply
to muscles.
VO2max Values
• VO2max of best human endurance athletes = 80-90
ml/kg/min, which equals that of pigs & rats, about
half that of horses & dogs, & a third that of foxes.
• VO2max of thoroughbred race horse = 150 ml/kg/min. So,
compared to a horse, even an Olympic champion looks like a
couch potato!
• Among all animals, flying insects have highest
VO2max relative to their size.
• VO2 of hummingbird flapping its wings 80 beats/min is 40
ml/gram/hour which, in human terms, equals 666 ml/kg/min!
• VO2 of honeybee flapping its wings 250 beats/min is 6
ml/gram/min, which equals 6,000 ml/kg/min!
VO2max Intervals
Provides greatest cardiovascular load
because you repeatedly reach & sustain
maximum stroke volume, cardiac output,
& VO2max during work periods.
Purposes:
• Increase max SV, max CO, & VO2max
• the higher the VO2max, the higher the aerobic ceiling
Recommendations:
• 3-5 min work periods with 1:≤1 work-to-rest ratio
• (short intervals with very short, active recovery
periods)
Work Periods
VO2max
(HRmax)
VO2
(HR)
Recovery Periods
Reps
VO2max Pace
• Running velocity that elicits VO2max
(vVO2max)
• Fastest speed that can be maintained for
~7-10 min
• 95-100% max HR
• Slower/recreational runners:
• 1- to 1½-mile race pace
• Highly-trained/competitive runners:
• 3K (2-mile) race pace
VO2max Interval Workouts
• 4 x 1,000 meters @ vVO2max with a 1:≤1 work:rest ratio
• 6 x 800 meters @ vVO2max with a 1:≤1 work:rest ratio
• 16 x 400 meters @ vVO2max with a 1:<1 work:rest ratio
If you can run 1½ miles in 10:00 (= 6:40 mile pace):
• 4 x 1,000 meters in 4:10 with 3:00 jog recovery
• 6 x 800 meters in 3:20 with 2:30-3:00 jog recovery
• 16 x 400 meters in 1:40 with :50 jog recovery
Although tempting to run faster when intervals are shorter, pace
should be same for all 3 workouts since goal is same—to improve
VO2max. As you progress, make workouts harder by adding
more reps or decreasing recovery period rather than by running
faster. Only increase speed of intervals once races have shown
that you are indeed faster.
Training VO2max
• While short intervals can improve VO2max, long
intervals run at 95-100% VO2max are most potent
stimulus.
• The more highly-trained the athlete, the more important
intensity becomes to improve VO2max.
• The more aerobically fit the athlete, the faster the
recovery both within & between interval workouts,
which 1) allows athlete to complete more reps during
each workout, thus enabling him/her to spend more
time at vVO2max, & 2) allows athlete to run interval
workouts more often.
LT Pace
• Slower/recreational runners:
• 10-15 sec/mile slower than 5K race pace (or
~10K race pace)
• 75-80% max HR
• Highly-trained/competitive runners:
• 25-30 sec/mile slower than 5K race pace (or
15-20 sec/mile slower than 10K race pace)
• 85-90% max HR
• Subjectively feel “comfortably hard”
LT Workouts
Continuous LT Runs
3-4 miles up to 7-8 miles (or ~45 min)
LT Intervals
intervals @ LT pace with short rest periods
4 x 1 mile @ LT pace w/ 1 min rest
LT+ Intervals
short intervals @ slightly faster than LT pace with very short
rest periods
2 sets of 4 x 1,000 meters @ 10 sec/mile faster than LT pace
w/ 45 sec rest & 2 min rest between sets
LT/LSD Combo Run
medium-long runs with portion @ LT pace
12-16 miles w/ last 2-4 miles @ LT pace
2 miles + 3 miles @ LT pace + 6 miles + 3 miles @ LT pace
Training Lactate Threshold
• Best stimulus to improve LT is continuous or
interval-type training performed at, or slightly
faster than, current LT pace.
• Among hardest types of workouts for runners to
do correctly, so monitoring by coach is essential.
• LT training is the best aerobic bang for your buck.
• LT training makes what was an anaerobic intensity
before now high aerobic.
• The longer the race, the more important it is to
train LT.
Training Running Economy
• High mileage (>70 miles per week) seems to
improve running economy.
• optimized biomechanics
• hypertrophy of Type I skeletal muscle fibers
• greater skeletal muscle mitochondrial & capillary
volumes
• greater ability for tendons to store & utilize
elastic energy
• lower body mass
• optimized motor unit recruitment patterns gained
from countless repetitions of running movements
Training Running Economy
• Higher intensity training (e.g., intervals &
tempo runs) has been shown to improve
economy.
Franch et al. (1998):
• 3.1% sig. improvement following tempo running
(20-30 min @ 90% max HR, 3 x wk for 6 wks)
• 3.0% sig. improvement following long intervals
(4-6 x 4:00 w/2:00 rest)
• 0.9% non-sig. improvement following short intervals
(30-40 x 15 sec. w/15 sec. rest)
Training Running Economy
Weight Training & Plyometrics
Research has shown that weight training using near
maximum loads & plyometric training can improve
economy by improving muscle power.
Power = Force x Velocity
Heavy weight training (e.g., 3-5 sets of 3-6 reps @
≥ 90% 1-rep max with 5 min rest) targets the force
(strength) component of power.
Plyometric training targets the velocity (speed)
component of power.
Training Running Economy
Weight Training & Plyometrics
• Studies found that neither VO2max nor LT
changed.
• suggests that improvements in economy from
power training do not result from cardiovascular
or metabolic changes, but rather from some other
(neural) mechanism
• Studies found increase in 1-rep max.
• Subjects didn’t gain weight.
• strength acquired through neural
adaptation, rather than hypertrophy
Training Running Economy
• Improved economy may be most significant
attribute gained from running high mileage.
• Adding long intervals to baseline mileage
can improve economy.
• Because runners are most economical at
speed at which they train the most, they
should spend time training at race pace to
improve economy at race pace.
• Heavy strength training & plyometrics
improve economy, possibly by neural
mechanism.
Muscle Morphology
Fiber Type
Type I
Type IIA
Type IIB
Slow-Twitch
Fast-Twitch A
Fast-Twitch B
1) Change characteristics of each fiber type
2) Change area taken up by fiber type
3) Conversion of fiber types?
• Increasing % of ST fibers would increase aerobic power &
capacity because ST fibers contain more mitochondria &
aerobic enzymes.
We combat fatigue by making muscles act as much
like ST fibers as we can by causing 1, 2, &/or 3.
Muscle Morphology
Fiber Type
Changes in Muscle Fiber Type Before and After Training
Pre-training
Post-training
% Type I Fibers
45.8 (6.9)
36.2 (4.3)*
% Type II Fibers
54.2 (6.9)
63.8 (4.3)*
Avg. Diameter Type I (m)
50.7 (0.8)
52.7 (1.0)
Avg. Diameter Type II (m)
57.9 (2.0)
57.8 (3.8)
% Area Type I Fibers
43.0 (6.6)
34.4 (4.0)*
% Area Type II Fibers
57.0 (6.6)
65.6 (4.0)*
Data from Dawson et al. (1998). *Significantly different from pre-training values (p<0.05).
Training consisted of sprint intervals (20-40 x 30-80m @ 90-100% max speed w/1:6 work:rest
ratio, decreasing to 1:4 ratio as training progressed) 3 x week for 6 weeks.
Acidosis/Metabolite Accumulation
Workouts that use anaerobic glycolysis
as predominant energy system and
repeatedly cause acidosis to improve
acidosis tolerance, muscle buffering
capacity, and anaerobic capacity.
Training Anaerobic Capacity
Examples of Workouts
• Intervals from 45 seconds to ~2 min (300800 meters) w/ either short or long
recovery
• short recovery keeps acidosis level high
throughout workout
• long recovery allows for even greater degree
of acidosis
• 6-8 x 400 meters @ mile race pace w/1:1
work:rest ratio
• 2 sets of 5 x 300 meters @ 800m race pace
w/1:2 work:rest ratio & 5:00 between sets
H+ + HCO3-  H2CO3  CO2 + H2O
CNS/Neuromuscular Fatigue
Power training with weights,
sprints, & plyometrics to increase
motor unit recruitment &
rate of force development.
Sample Plyometric Program
To get the most out of plyometric training, try to spend as little time on the ground as possible between
hops/bounds/jumps. Do exercises on a soft surface, such as grass, a track, or a gymnastic mat. Begin with two
sessions per week of two sets of ten repetitions (2 x 10) with full recovery between sets.
Week
Single leg
hops
Bleacher
hops
Double leg
bound
Alternate
leg bound
1
2 x 10
2 x 10
2
2 x 10
2 x 10
3
2 x 10
4
Squat
jumps
Depth
jumps
Box
jumps
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
5
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
6
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
2 x 10
Single leg hops: 1) On one leg, hop up and down; 2) hop forward and back; 3) hop side-to-side.
Bleacher hops: Standing at the bottom of the bleacher steps on one leg, hop up the steps. Walk back down and hop
up again on the other leg.
Double leg bound: From a squat position with both legs, jump forward as far as you can.
Alternate leg bound: In an exaggerated running motion, bound (which looks like a combination of running and
jumping) forward from one leg to the other.
Squat jumps: With hands on hips in a squat position, jump straight up as high as you can. Upon landing, lower back
into a squat position in one smooth motion, and immediately jump up again.
Depth jumps: From a standing position on a one-foot tall box, jump onto the ground and land in a squat position.
From this squat position, jump straight up as high as you can.
Box jumps: From the ground, jump with two feet onto a box about one foot high, and then immediately jump into
the air and back down to the ground. As you get experienced with the exercise, try jumping with one foot at a time.
Marathon Fatigue
• Glycogen Depletion
• long runs (>2 hrs) & LT/LSD combo runs to
deplete muscle glycogen
• causes greater synthesis & storage
• causes greater reliance on fat
• stimulates liver gluconeogenesis
• Since recovery is closely linked to
replenishment of carbohydrates,
consume carbs immediately afterward.
Marathon Fatigue
• Dehydration
• drink fluids w/sodium during marathon
• Muscle Fiber Damage
• do long runs on pavement
• Hyperthermia
• acclimatize (~14 days) by running in heat
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