The Causes of Fatigue and How to Combat

Them

2012 Northern California All-Sports Clinic

© Jason Karp, Ph.D.RunCoachJason.com

Founder/Coach, REVO2LT Running TeamTM

Freelance writer & author2011 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 O2-independent ATP regeneration is delayed.

The 3 Players of Distance Running

R E

VO2

L T

unning

conomy

max

actate

hreshold

maximum volume of O2 consumed per minute

speed above which lactate accumulates & acidosis occurs

O2 cost of maintaining a given pace

• 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.

VO2ma

x

• 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

What Determines VO2max?

Transporting oxygen from the heart to the muscles is a complicated matter!

• 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.

What Determines VO2max?

Fick Equation

Central factors

Peripheral factors

VO2 = SV x HR x (a-v O2 difference)

VO2 = CO x (a-v O2 difference)

VO2max occurs when SV, HR (and therefore cardiac output), & a-v O2 difference are at maximum.

• 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.

Central vs. Peripheral Limitation?

• 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 Values

VO2max Intervals

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)

Provides greatest cardiovascular load because you repeatedly reach & sustain maximum stroke volume, cardiac output, & VO2max during work periods.

Work Periods

VO2

(HR)

VO2max (HRmax)

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

• 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

VO2max Interval Workouts

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 Runs3-4 miles up to 7-8 miles (or ~45 min)

LT Intervals intervals @ LT pace with short rest periods4 x 1 mile @ LT pace w/ 1 min rest

LT+ Intervalsshort intervals @ slightly faster than LT pace with very short rest periods2 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 Runmedium-long runs with portion @ LT pace12-16 miles w/ last 2-4 miles @ LT pace 2 miles + 3 miles @ LT pace + 6 miles + 3 miles @ LT pace

• 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 Lactate Threshold

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)

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

Power = Force x Velocity

Research has shown that weight training using near maximum loads & plyometric training can improve economy by improving muscle 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 MorphologyFiber Type

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.

Type I Type IIA Type IIBSlow-Twitch Fast-Twitch A Fast-Twitch B

Muscle Morphology Fiber Type

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.

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)*

Changes in Muscle Fiber Type Before and After Training

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

H+ + H2CO3 CO2 + H2O

• Intervals from 45 seconds to ~2 min (300-800 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

HCO3-

CNS/Neuromuscular Fatigue

Power training with weights, sprints, & plyometrics to increase motor unit recruitment &rate of force development.

Sample Plyometric ProgramTo 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

Squat jumps

Depth jumps

Box jumps

1 2 x 10 2 x 10

2 2 x 10 2 x 10

3 2 x 10 2 x 10 2 x 10 2 x 10

4 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

References & Recommended ReadingsAcevedo, E.O. and Goldfarb, A.H. (1989). Increased training intensity effects on plasma lactate, ventilatory threshold, and endurance. Medicine and Science in Sports and Exercise. 21(5):563-568.

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Billat, V.L. (2001). Interval training for performance: a scientific and empirical practice. Special recommendations for middle- and long-distance running. Part I: aerobic interval training. Sports Medicine. 31(1):13-31.

Billat, V.L. (2001). Interval training for performance: a scientific and empirical practice. Special recommendations for middle- and long-distance running. Part II: anaerobic interval training. Sports Medicine. 31(2):75-90.

Billat, V.L., Demarle, A., Paiva, M., and Koralsztein, J-P. (2002). Effect of training on the physiological factors of performance in elite marathon runners (males and females). International Journal of Sports Medicine. 23:336-341.

Billat, V.L., Flechet, B., Petit, B., Muriaux, G., and Koralsztein, J-P. (1999). Interval training at VO2max: effects on aerobic performance and overtraining markers. Medicine and Science in Sports and Exercise. 31(1):156-163.

Burke, J., Thayer, R., and Belcamino, M. (1994). Comparison of effects of two interval-training programmes on lactate and ventilatory thresholds. British Journal of Sports Medicine. 28(1):18-21.

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Cunningham, D.A., McCrimmon, D., and Vlach, L. (1979). Cardiovascular response to interval and continuous training in women. European Journal of Applied Physiology. 41(3):187-197.

Daniels, J. (1989). Training distance runners—a primer. Sports Science Exchange. 1(11). Chicago: Gatorade Sports Science Institute.

References & Recommended Readings

Daniels, J. (2005). Daniels’ Running Formula. Champaign, IL: Human Kinetics.

Eddy, D.O., Sparks, K.L., and Adelizi, D.A. (1977). The effects of continuous and interval training in women and men. European Journal of Applied Physiology. 37(2):83-92.

Esfarjani, F. and Laursen, P.B. (2007). Manipulating high-intensity interval training: Effects on VO2max, the lactate threshold and 3000m running performance in moderately trained males. Journal of Science and Medicine in Sport. 10:27-35.

Farrell, P.A., Wilmore, J.H., Coyle, E.F., Billing, J.E., and Costill, D.L. (1979). Plasma lactate accumulation and distance running performance. Medicine and Science in Sports and Exercise. 11(4):338-344.

Franch, J., Madsen, K., Djurhuus, M.S., and Pedersen, P.K. (1998). Improved running economy following intensified training correlates with reduced ventilatory demands. Medicine and Science in Sports and Exercise. 30(8):1250-1256.

Hamel, P., Simoneau, J.A., Lortie, G., Boulay, M.R., and Bouchard, C. (1986). Heredity and muscle adaptation to endurance training. Medicine and Science in Sports and Exercise. 18(6):690-696.

Henritze, J., Weltman, A., Schurrer, R.L., and Barlow, K. (1985). Effects of training at and above the lactate threshold on the lactate threshold and maximal oxygen uptake. European Journal of Applied Physiology and Occupational Physiology. 54(1):84-88.

Hoff, J., Helgerud, J., and Wisløff, U. (1999). Maximal strength training improves work economy in trained female cross-country skiers. Medicine and Science in Sports and Exercise. 31(6):870-877.

Hoff, J., Helgerud, J., and Wisløff, U. (2002). Endurance training into the next millennium: muscular strength training on aerobic endurance performance. American Journal of Medicine and Sports. 4:58-67.

Jones, A.M. (1998). A five year physiological case study of an Olympic runner. British Journal of Sports Medicine. 32:39-43.

References & Recommended Readings

Jones, A.M. and Carter, H. (2000). The effect of endurance training on parameters of aerobic fitness. Sports Medicine. 29(6):373-386.

Karp, J.R., Johnston, J.D., Tecklenburg, S., Mickleborough, T.D., Fly, A.D., and Stager, J.M. (2006). Chocolate Milk as a Post-Exercise Recovery Aid. International Journal of Sport Nutrition and Exercise Metabolism. 16(1):78-91.

Keith, S.P., Jacobs, I., and McLellan, T.M. (1992). Adaptations to training at the individual anaerobic threshold. European Journal of Applied Physiology. 65(4):316-323.

Knuttgen, H.G., Nordesjo, L.O., Orlander, B., and Saltin, B. (1973). Physical conditioning through interval training with young male adults. Medicine and Science in Sports and Exercise. 5:220-226.

Lake, M.J. and Cavanagh, P.R. (1996). Six weeks of training does not change running mechanics or improve running economy. Medicine and Science in Sports and Exercise. 28(7):860-869.

Lesmes, G.R., Fox ,E.L., Stevens, C., and Otto, R. (1978). Metabolic responses of females to high intensity interval training of different frequencies. Medicine and Science in Sports and Exercise. 10(4):229-232.

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References & Recommended Readings

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