RESISTANCE EXERCISE

Resistance exercise is active exercise in which muscle contraction is resisted by an outside force. This outside force may be manual or mechanical.

Definition:

Regular resistive exercise is associated with several positive adaptations which is dosage dependent.

These changes include:

Physiological Adaptations to Resistive Exercise

Acute adaptations are changes that occur in the body during and shortly after an exercise bout.

Chronic adaptations are changes in the body that occur after repeated training bouts and that persist long after a training session is over

Basic Adaptations:

Early strength gains are often attributed to so called neural factors

It is believed to be the dominant influence in the 1st to 2nd month of a training program

Assumption from increased EMG amplitude measured during maximal contractions

Co-contraction – refers to the simultaneous activation of an agonist or antagonist during a motor task

Neurological Changes

Neurological Changes Happen prior to structural changes Increase in muscle recruitment (71% in untrained) Increase in firing rate Increase in the timing and discharge during high intensity muscular

contraction Increase in hypertrophy Lower activation threshold Increase in inhibition of antagonist (via GTOs) The Golgi Tendon Organ

◦ § Cocontraction Increase in Neuromuscular Junction Increase in Cross-education (Cross education is a neurophysiological phenomenon

where an increase in strength is witnessed within an untrained limb following unilateral strength training in the opposite, contralateral limb. Cross education can also be seen in the transfer of skills from one limb to the other.

◦ § Up to 22%◦ § Greater EMG

Bilateral deficit(The bilateral deficit is a phenomenon where the total force production of a bilateral lift (i.e. a squat, deadlift) will not be greater than the sum of individual efforts of a single limb.

Stretch Reflex Increase in spindle fiber activity by 19-55% Motor units are recruited according to their threshold of

firing rates Larger loads, greater muscle fiber recruitment The technique of recording electrical events

Electromyography EMG The process of skeletal muscle activation involves action

potential generation on the muscle cell membrane via acetylcholine release from the alpha motor neuron that innervates a particular muscle cell

The action potential is manifested as a voltage change on the sarcolemma that can be recorded with either surface or intramuscular electrodes

The primary adaptation of skeletal muscle to long-term resistance training is hypertrophy, or increased cross sectional area (CSA) of a muscle fiber, resulting in increased force and power production

During and immediately after resistance exercise, metabolites accumulate and fuel substrates are depleted; thus, clients need to include adequate CHO in their diets

Muscle Tissue Changes

1. Increase in CSA2. Due to in increase in synthesis and decrease in degradation of contractile proteins3. Increase in the number of myofibrils within a fiber4. Resistance training can alter up to 70 different genes

◦ § Increasing regeneration◦ § Down regulation of inhibitory growth factors

5. Protein synthesis is increased up to 48 hrs following RT6. Depends on availability of Carb, Pro, and Kcal

◦ § As well as nutrient timing, cell hydration, and mechanical stress of the RT

7. Fiber damage and disruption stimulate synthesis as well8. Increases are seen in both Type I and II fibers

◦ § Minimal in Type I9. Athletes who generally possess a relatively large proportion of Type II may have a greater potential for increasing muscle mass with RT10. We see a shift in fiber type due to RT

1. An increase in the number of fibers◦ § Via longitudinal fiber splitting◦  Hyperplasia is different from hypertrophy in that

the adaptive cell change in hypertrophy is an increase in cell size, whereas hyperplasia involves an increase in the number of cells.

2. Shown to occur in animals3. Debated in humans

Hyperplasia

Change in ATP and CP concentration seem to be very sensitive to the training mode…

High volume resistance training may induce glycolytic enzymatic adaptations that increase muscle endurance

Metabolic Changes

Hormones are blood-borne molecules that are produced ion the glands called the endocrine glands.

Anabolic – stimulate growth◦ ± Catabolic – tissue degradation to help

maintain homeostatis

Endocrine Changes

Osteoporosis – is the consequence of long-term net demineralization of bone

The greater the bone mass prior to menopause, the less severe are the consequences of loss of bone mass. Resistance training may lead to decreased risk for osteoporosis, fractures, and falls in later life

Skeletal Changes

Osteoblasts◦ New bone on Periosteum

Osteoclasts◦ Cells that break down bone◦ Decreased activity decrease bone mineral

density Stress is needed for bone to remodel

◦ Minimal Essential Strain

RT causes deformation of specific skeletal regions

Types of force from RT◦ Bending, compressive, and or torsional

Connective Tissue

Osteoblasts migrate to the area of stress◦ Secrete proteins into the space between cells and

increase the bone matrix◦ Sensitive to mechanical loading◦ Increases diameter and strength of the bone

The threshold for new bone growth must be met by the force generated by RT

Increase in muscular strength and hypertrophy cause and increase in force exerted on the bone◦ Causing a direct correlation with Bone Mineral

Density BMD and muscular strength and hypertrophy

◦ Starts within first few sessions but is a long process

Given the clear effect of resistance training on Fat free mass (increase) and its possible effects on resting muscle metabolic rate, resistance training should be a critical component of any comprehensive program to control body fat.

Body Composition

Increase in Fat Free Mass (FFM) Decrease in subcutaneous fat Caloric intake and metabolism are factors Cardiovascular exercise, Short term is

more effective in decreasing body fat

Specificity of loading should be used to target specific sites

Jumping will not cause a BMD increase in the ulna

The higher the impact the greater the BMD increase will be

Overload progression must be followed To fast will cause stress fractures Ideal to increase peak bone mass in early

adult hood

Increasing BMD

a. Intensity b. Speed c. Direction of force d. Volume of force

BMD increased by

Structural component of all is collagen fiber◦ a. A protein◦ b. Derived from parent protein procollegen from

the fibroblastsStimulus for growth is the mechanical forces created during RT

◦ a. The degree of adaptation is proportional to the force applied during RT

◦ b. Needs to exceed threshold of strain

Tendons, Ligaments, Fascia, and Cartilage

Increases strength and load bearing by

◦a. Increasing the junction between the tendon or ligament and bone surface

◦b. Increasing the strength of the body of tendon or ligament

◦c. Increasing the network of fascia within the skeletal muscle

Connective Tissue

Stronger muscle pulls with greater force on their bony attachments causing in increase in bone mass at the tendon bone junction

Increase in collagen fibril diameter A greater number of covalent cross links

within the hypertrophied fiber An increase in the number of collagen

fibrils An increase in the packing density of

collagen fibrils◦ RT increase tendon stiffness

Only with heavy loads of 80% RM

Changes within the Tendon

Function◦ Provide smooth joint articulating surface◦ Act as shock absorption◦ Aid in attachment of connective tissue

Does not have its own blood supply◦ Gets nutrients through diffusion from synovial

fluidRT will increase the thickness of the cartilage that experiences weight bearing

◦ The heavier the thicker

Changes within Cartilage

Resistance training with aerobic endurance training can improve the ability of the heart, lungs, and circulatory system to function under conditions of high pressure and force productions

Acute (exercise) Increase in

◦ § HR◦ § SV◦ § Q◦ § BP

Have seen peaks of 320/250 mmHg an 208 b/m during high intensity RT

Chronic while RT Blunted increases in HR and BP

Cardio Vascular Changes

Ventilation generally does not limit RT At most moderately improved by RT Unless RT is done as a circuit

◦ Ventilation levels are highest directly following the performance of an exercise

◦ ± Some increases have been seen in tidal volume and breathing frequency as well as ventilation equivalent

Ventilation Changes

± Adding aerobic training to RT will decrease the ultimate effects of RT

o Strength power and hypertrophy ± Most studies have shown no adverse

effects of adding RT to aerobic training ± With the combination of Aerobic and

Anaerobic the risk of overtraining is increased

Compatibility of Anaerobic and Aerobic Training

1. Specificity 2. Sex 3. Age 4. Genetics

Factors that influence adaptations to resistance training

overtraining is a physical, behavioral, and emotional condition that occurs when the volume and intensity of an individual's exercise exceeds their recovery capacity. They cease making progress, and can even begin to lose strength and fitness.

Overtraining is a common problem in weight training, but it can also be experienced by runners and other athletes.

Overtraining

Plateau followed by a decrease of strength gains Sleep disturbances Decrease in lean body mass Decreased appetite A cold that doesn’t go away Flu like symptoms Loss of interest Mood Changes Excessive muscle soreness

Overtraining

Detraining refers to the bodily effect experienced when one takes an extended break from regular, vigorous fitness training. Fitness levels and muscle mass can decline during a break that lasts between two and four weeks. While this sort of long-term break may reduce current fitness levels, it may also offer long-term benefits if the person starts retraining, allowing them to achieve higher levels of fitness than before detraining. Atrophy in the fast-twitch muscle

occurs faster

Detraining