C HAPTER 3 NEUROMUSCULAR ADAPTATIONS TO RESISTANCE TRAINING

Measuring Muscular Performance Strength—the maximal force a muscle or muscle group can generate. Power—the product of strength and the speed of movement. Muscular endurance—the capacity to sustain repeated muscle actions.

One-Repetition Maximum (1-RM) The maximal weight an individual can lift just once. Can be estimated submaximally Eppley Equation: 1RM = (0.033 Reps) Rep Wt. + Rep Wt. Choose a weight that is about a 10RM load. There are many other equations and tables.

Are Men Stronger than Women? Females 50-80% as strong (forearm 50%; hip 80%) Why are men stronger? Is it structural or simply because they are bigger?

Gender differences Strength/Unit of Body Weight (relative term which removes the influence of BW) –Men still stronger –Women have a higher proportion of their body weight which is fat and fat does not contribute to strength

Gender Differences Strength/Unit of Fat-Free Weight (determined body composition by under water weighing) –Men are still stronger per unit of FFW –A higher proportion of male FFW is muscle (FFW isn’t just muscle it is tendons, organs, bones etc…)

Gender Differences Strength/Unit of Muscle Mass –Use MRI to determine muscle mass using the cross-sectional area of the muscle –Men are no longer stronger than women –There is no structural difference in male and female muscle that allows men to produce more strength than women.

STRENGTH CHANGES IN WOMEN

Power  The functional application of strength and speed  The key component of many athletic performances  Power = (force 5 distance)/time

Muscular Endurance  Can be evaluated by noting the number of repetitions you can perform at a given percentage of your 1-RM  Is increased through gains in muscular strength  Is increased through changes in local metabolic and circulatory function

Muscular Endurance  Sit-ups  Supine position  Fingers touching masking tape  Another piece of tape placed 12cm beyond the first piece  Metronome set at 40 beats/min  Perform as many curl-ups as possible to a max of 75

Muscular Endurance  Push-ups  Males in up position  Females in modified knee position  Lower body until chin touches mat  Max numer of push-ups consecutively

Muscular Endurance   Test Battery %Body Weight to be liftedRep-15 MenWomen Arm Curl Bench Press Lat Pull-Down TricepsExtension Leg Extension Leg Curl Bent Knee Sit-upsMaxMax Total_________

Muscular Endurance Total RepsFitness Category Excellent 77-90Very Good 63-76Good 49-62Fair 35-48Poor <35Very Poor

Muscle Size  Hypertrophy refers to increases in muscle size.  Atrophy refers to decreases in muscle size.  Muscle strength involves more than just muscle size.

Results of Resistance Training  Increased muscle size (hypertrophy).  Alterations of neural control of trained muscle.  Studies show strength gains can be achieved without changes in muscle size, but not without neural adaptations.

Possible Neural Factors of Strength Gains  Recruitment of additional motor units for greater force production  Counteraction of autogenic inhibition allowing greater force production  Reduction of coactivation of agonist and antagonist muscles  Changes in the discharge rates of motor units  Changes in the neuromuscular junction

Muscle Hypertrophy Transient—pumping up of muscle during a single exercise bout due to fluid accumulation from the blood plasma into the interstitial spaces of the muscle. Chronic—increase of muscle size after long-term resistance training due to changes in muscle fiber number (fiber hyperplasia) or muscle fiber size (fiber hypertrophy).

Fiber Hypertrophy  The numbers of myofibrils and actin and myosin filaments increase, resulting in more cross-bridges.  Muscle protein synthesis increases during the postexercise period.  Testosterone plays a role in promoting muscle growth.  Training at higher intensities appears to cause greater fiber hypertrophy than training at lower intensities.

Fiber Hyperplasia  Muscle fibers split in half with intense weight training.  Each half then increases to the size of the parent fiber.  Satellite cells may also be involved in skeletal muscle fiber generation.  It has been clearly shown to occur in animal models; only a few studies show this occurs in humans too.

RESISTANCE TRAINING IN CATS

SPLITTING MUSCLE FIBER

Neural Activation and Fiber Hypertrophy  Early gains in strength appear to be more influenced by neural factors.  Long-term strength increases are largely the result of muscle fiber hypertrophy.

MODEL OF NEURAL AND HYPERTROPHIC FACTORS

Did you Know? If you train one limb but not the other, the untrained limb will get stronger % increase in the trained limb 5-15% increase in the untrained limb

Cross-training Implications for rehab?

Cross-training Neural or Hypertrophy?

Cross-Training Why do we get stronger? 1. Posturing Theory – as contract leg, are also contracting muscles in opposite leg to maintain balance. 2. Neuroanatomy - ~80% of neurons cross- over, 10-20% do not. 3. Increased enzymes increase your ability to store glycogen in other limb.

Cross-training This was discovered originally in children tracing shapes with one hand. They got better at it with the other hand even though they never used that hand.

Effects of Muscular Inactivity  Muscular atrophy (decrease in muscle size)  Decrease in muscle protein synthesis  Rapid strength loss

Acute Muscle Soreness  Results from an accumulation of the end products of exercise in the muscles  Usually disappears within minutes or hours after exercise

Delayed-Onset Muscle Soreness (DOMS)  Results primarily from eccentric action  Is associated with damage or injury within muscle  May be caused by inflammatory reaction inside damaged muscles  May be due to edema (accumulation of fluid) inside muscle compartment  Is felt 12 to 48 hours after a strenuous bout of exercise

DOMS and Performance  DOMS causes a reduction in the force-generating capacity of muscles.  Maximal force-generating capacity returns after days or weeks  Muscle glycogen synthesis is impaired with DOMs

Reducing Muscle Soreness  Reduce eccentric component of muscle action during early training  Start training at a low intensity, increasing gradually  Begin with a high-intensity, exhaustive bout of eccentric- action exercise to cause much soreness initially, but decrease future pain

1. Consider different dynamic training programs. 2. Perform a training needs analysis. 3. Select appropriate resistance levels. Designing Resistance Training Programs 4. Decide on single sets versus multiple sets. 5. Design a training program using periodization. 6. Assign specific forms of resistance training depending on the sport or desired results.

Resistance Training Actions Static (isometric) actions Dynamic actions  Free weights  Eccentric training  Variable resistance  Isokinetic actions  Plyometrics Electrical stimulation training

Needs Analysis  What muscles need to be trained?  What method of training should be used?  What energy system should be stressed?  What are the primary sites of concern for injury prevention?

Selecting the Appropriate Resistance Strength—few reps and high resistance (6-RM) Muscular endurance—many reps and low resistance (20-RM) Power—several sets of few reps and moderate resistance; emphasize speed of movement Muscle size—more than 3 sets of 6-RM to 12-RM loads; short rest periods

Periodization Periodization prevents over-training by varying the volume and intensity Used for strength and power sports Cycle of five phases: four active phases followed by one active recovery phase Each phase gradually decreases volume and gradually increases intensity Two cycles per year

Periodization Phase I – hypertrophy –Sets 3-5 –Reps 8-20 –Intensity Low –Duration 6 weeks

Periodization Phase II – strength –Sets 3-5 –Reps 2-6 –Intensity high –Duration 6 weeks

Periodization Phase III – power –Sets 3-5 –Reps 2-3 –Intensity high –Duration 6 weeks

Periodization Phase IV – peaking –Sets 1-3 –Reps 1-3 –Intensity Very High –Duration 6 weeks

Periodization Phase V – recovery –General activity or light resistance training –2 weeks