HSS 395 Responses & Adaptations to Resistance Training

Resistance training

A form of exercise that increases muscular strength and/or endurance by applying resistance to the muscles/muscle groups

• Resistance can come in the form of gravity, bodyweight, or an external load

Basics of adaptations in resistance training

1. Resistance training → stress response

2. Progressive overload = adequate stress

3. Chronic adaptations: strength → mass → bone density

4. Individuals respond differently to training

Acute responses

Responses that occur during and shortly after a training session

Chronic adaptations

Changes that occur after repeated training sessions and persist over time; summation of acute responses catalyzes chronic adapations

• Optimal adaptations occur when progressive overload is used

Acute responses — neurological

Alterations in recruitment and firing rate of motor units during a set due to fatigue

• Size principle: motor units are recruited from smallest to largest

Acute responses — muscular

Production of ATP results in…

• Accumulation of metabolites (lactate, H+, P_i, ammonia)

• Depletion of fuel substrates (creatine phosphate, glycogen)

Acute responses — endocrine

• Initial phases (3-4 weeks): relatively equal synthesis (anabolic hormones) and breakdown of muscle protein

• Later phases: protein synthesis outpaces breakdown due to a greater response to anabolic hormones

What type of training creates a greater anabolic hormone response?

• Higher volume

• Shorter rest

• Larger muscle mass exercises

Chronic adaptations — neurological

Linked to strength gains in first 1-2 months…

• Improved form & technique

• Increased motor unit recruitment and firing rate

• Increased motor unit synchronization

• Decreased cocontraction

• Changes in motor unit excitability

Chronic adaptations — muscular

• Hypertrophy: increased cross-sectional area of muscle

  • Greater in Type II fibers

  • Increased number of myofibrils and structural proteins

• Fiber subtype shift: Type IIx → Type IIa

Chronic adaptations — skeletal changes

Increased bone mineral density affected by strain magnitude and strain rate; potential decreased risk for osteoporosis

Chronic adaptations — tendons

Increased strength (adapt to loads applied)

Chronic adaptations — ligaments

Little data on ligament changes

Chronic adaptations — cartilage

Effects on cartilage are inconclusive, however, training is an effective treatment for osteoarthritis

Chronic adaptations — metabolic

• NO CHANGE in number of mitochondria & decreased mitochondrial density

• Increases in creatine kinase & glycolytic enzymes → increased endurance capacity of muscles

Chronic adaptations — endocrine

• NO CHANGE in resting hormone concentrations

• Increased magnitude of response and sensitivity of tissues to hormones

Chronic adaptations — cardiorespiratory changes

• Limited effects on cardiorespiratory fitness (dependant on age and pre-existing fitness levels)

• No negative effects on development of VO₂ max

• Can augment aerobic endurance performance by increasing strength and power

Chronic adaptations — body composition

• Increased fat-free mass

• May decrease fat ass over time

• Inconclusive evidence on significantly increasing metabolic rate

Influencing factors — specificity

Adaptations are specific to the exercise stressor (including velocity of muscle action during contraction)

Influencing factors — sex

Males and females respond similarly to training

• Sex-related differences in strength are larger in upper body than lower

• Relative strength is similar, however, absolute strength is greater in men

Influencing factors — age

Sarcopenia: age-related loss of muscle mass after age 30

• Declines in ability to produce force

• Can be moderated/reversed with high-intensity resistance training

Influencing factors — genetics

Genetics may play a role in the ability to adapt to resistance training

Overtraining

A condition in which an individual train excessively (inappropriate volume/intensity); leads to decreased neuromuscular performance, mood changes, lethargy, and strength plateaus

• Only treatment = REST (days, weeks, or months)

Detraining

Physiological and performance adaptations that occur when an individual ceases an exercise training program; adaptations are opposite of those from training (loss of muscle mass, strength, & power)

Short-term detraining

14 days — little effect on muscular strength & explosive power in those who are resistance-trained

Extended detraining

48 weeks — significant decreases in muscular strength