Exercise Science: Resistance Training Concepts

Adaptations to Exercise Training

• Learning objectives include defining muscular strength, power, and endurance. Examining strength training principles, how strength is gained through resistance training and changes in muscle structure and neural mechanisms during resistance training. Learning about muscle soreness and its prevention, as well as strength training differences between women and men and younger and older persons.

Defining Muscular Performance - Strength

• Muscular strength is the maximal force a muscle or muscle group can generate in a single contraction. This is measured as 1-RM (1 Repetition Maximum).
• Muscular strength is related to muscular endurance. As muscle strength increases, muscle endurance also increases.

Force Generation

• Muscle force generation depends on: muscle size, type of muscle contraction, number of muscle fibers activated, the nervous system's ability to activate fibers, and the person's motivation.
• Strength potential is genetically limited by the number of fast twitch fibers.

Evaluating Strength

• 1-RM tests measure the maximum weight a person can lift in one complete repetition with proper technique.
• Types of 1-RM tests include isokinetic, eccentric, and isotonic.
• Research shows a strong positive correlation between isotonic, eccentric, and isokinetic strength measurements.

Correlations

• Correlation coefficients (r) measure the strength and direction of a linear relationship between two variables.
• r values range from -1.0 to +1.0. Values closer to +1 or -1 indicate a stronger relationship.
• Coefficient of determination (R²) represents the proportion of variance in one variable that can be explained by the other. Example: R² = 0.85 indicates 85% of the variation in one variable is explained by the other.
• P values indicate the statistical significance of a relationship. A p value of <0.05 is considered statistically significant.

Predicting 1-RM for Exercise Prescription

• Muscular strength and endurance are related, so 1-RM can be estimated without a maximal lift.
• A common method involves a 6-10 RM (repetition maximum) test.
• Estimate 1-RM, warm-up to 40-60% of the estimated 1-RM, stretch, perform sets at 60-80% of estimated 1-RM. Increase weight if more than 10 reps are possible.
• Calculate 1-RM from appropriate charts.

Predicted 1-RM Calculation

• Determine the percentage of 1-RM from the number of reps completed.
• Divide the weight lifted by the percentage.
• Example: If 8 reps of 100 pounds are performed, then 1-RM = (100 lbs)/0.80 = 125 lbs

Defining Muscular Performance - Muscular Endurance

• Muscular endurance is the body's ability to sustain repeated muscle actions or a single static contraction, which can be improved by using moderate loads and increasing the number of repetitions.
• A muscle that fatigues rapidly has a low endurance capacity. Women often outperform men in endurance tests, especially at lower workloads.

Evaluating Muscular Endurance

• Various tests evaluate muscular endurance, including repeated contractions like partial curl-ups; sustained contractions, such as isometric exercises and back extensions; and dynamic endurance tests such as partial curl-ups with a set cadence, lifting a certain weight at a specific cadence, and relative load endurance.

Defining Muscular Performance - Muscular Power

• Muscular power is the product of strength and the speed of movement. If two individuals can lift the same amount of weight, the one that lifts it faster exhibits more power.
• Power = force x distance / time (strength x speed or velocity).

Muscular Power

• Peak muscular power increases as force and movement velocities increase up to a maximum point.
• Beyond this maximum, power decreases due to a reduction in force at faster movements.
• The relationship between a muscle's maximal power output and its velocity (speed) is an inverted U-shaped curve. Power increases with increasing velocity and force until a maximum is reached, after which it decreases.

Principle of Overload

• Muscles must be loaded beyond their normal load to gain strength.

Principle of Progressive Resistance Training

• As muscles get stronger, progressively greater resistance is required to stimulate further gains in strength.

Stress-Rest Principle

• One day of exercise ideally followed by one day of rest. High intensity training (hard day) should be followed by a low intensity training (easy day) to allow the body to recover
• Too much training leads to a failure to recover. Too much rest can lead to no improvement. A minimum of 48 hours of rest between muscle group workouts is sometimes recommended.

Principle of Symmetry

• Emphasizes balanced development of the entire body. Balanced training results in better overall conditioning, performance, and outcomes.

Principle of Specificity (SAID Principle)

• Training adaptations are specific. The type of activity, intensity, and volume of exercise matter most; targeted adaptations will show up most quickly. A high jumper should not solely train in endurance running events. The training program should target the physiological systems needed for optimal performance in the sport in question.

Principle of Contraction Control

• Weight should be raised and lowered slowly, in a controlled manner. A recommended guideline is to take 2-4 seconds for each movement.

Ceiling Principle

• As fitness levels increase, strength and endurance increase. Increases tend to become smaller as the potential limit is reached.

Principle of Reversibility

• "Use it, or lose it." Training gains will be lost without continued exercise. The rate of loss to a cessation of exercise can be as high as 1:3 (i.e., for every 1 unit of training lost, 3 units of strength may be lost.

FITT Principle

• Frequency, Intensity, Time, and Type.
• Common example used to determine a starting resistance training program.

Maintenance Principle

• Maintaining achieved fitness levels involves continuing the current intensity, duration, and frequency of training (or slightly reducing intensity, duration, or frequency). Maintenance programs may allow for reductions in the volume and intensity of resistance training for a period of time (typically at least 12 weeks) while still maintaining gains in muscle strength.

Principle of Individuality

• Training programs must be adapted to individual needs due to different responses to similar training programs.

Principle of Periodization

• Gradual cycling of the volume, intensity, and type of training to promote peak performance for competitions while avoiding overtraining. Includes macrocycles (months), mesocycles (weeks), microcycles (days), and individual workouts.

Resistance Training Programs: Key Points

• Low-repetition, high-resistance training promotes muscle development, while high-repetition, low-resistance training optimizes endurance. Effective resistance training programs should consider the type of contractions.

Adaptations to Resistance Training

• Muscle strength incorporates greater than just muscle size, and neural control/motor unit recruitment is likewise significant. Early gains in strength are more closely linked to neural adaptations. Long-term strength increases are primarily due to muscle fiber hypertrophy along with cellular adaptations requiring at least 8-12 weeks of training to see notable gains. Women experience similar strength gains as men, but hypertrophy is less pronounced in women.

Muscle Size and Strength

• Mechanisms of gains in muscle strength from resistance training include neural control and muscle hypertrophy. Increased neural control contributes to improved muscle strength through improved synchronization and recruitment of motor units; more rapid motor unit discharge; reduced co-activation of agonist and antagonist muscles; and autogenic inhibition. Increased muscle size means increases in the number and size of myofibrils per muscle fiber and an increase in contractile proteins. There is a positive relationship between increasing muscle cross-sectional area and strength.

Mechanisms of Gains in Muscle Strength from Resistance Training

• Increased synchronization and recruitment of additional motor units.
• Increased frequency of discharge (rate coding) of motor units.
• Autogenic inhibition.
• Reduction in coactivation of agonist and antagonist muscles.

Muscle Hypertrophy

• Transient hypertrophy refers to the "pumping up" effect of muscles due to fluid accumulation during a single bout of exercise.
• Chronic hypertrophy is an increase in muscle size after long-term resistance training, resulting from either increased fiber number (hyperplasia) or increased fiber size (hypertrophy).

Fibre Hypertrophy

• Increased number and size of myofibrils per muscle fibre.
• Increased amount of contractile protein (actin and myosin) leading to more cross-bridges.
• Increased amount and strength of connective tissue.
• Increased sarcoplasm (glycogen, myoglobin).
• Increase in muscle protein synthesis during the post-exercise period; testosterone plays a crucial role in promoting muscle growth.

Muscle Atrophy and Decreased Strength with Inactivity

• Decrease in muscle size.
• Decrease in muscle protein synthesis.
• Rapid strength loss.
• Reasons for muscle atrophy include immobilization, stopped training, reduced training, and inadequate food energy.

Muscle Atrophy due to Cessation of Training in Women

• Reduced strength in women undergoing detraining. Women show similar responses of muscle strength loss compared to men, differing only significantly around 6 weeks into detraining. Significant declines in strength occur between 20 weeks of training and 32 of detraining and can be restored relatively quickly.

Changes in mean cross-sectional areas for fibre types

• Resistance training often affects overall muscle cross-sectional area and the quantity of fibre types. Maintaining training often keeps FT fibres relatively consistent while ST fibres can be somewhat affected.

Muscle Soreness

• Two types of muscle soreness exist: acute and delayed onset muscle soreness (DOMS).

Acute Muscle Soreness

• Occurs during or immediately following exercise.
• Thought to be associated with a lack of blood flow (ischemia) and accumulation of metabolic waste products, such as lactic acid and potassium, that cannot be removed from the muscles efficiently.
• Usually disappears within minutes to hours once exercise intensity is reduced.

Delayed Onset Muscle Soreness (DOMS)

• Felt 12 to 48 hours after strenuous exercise, primarily due to eccentric muscle actions which cause stress on tendons and muscles.
• May be caused by inflammatory responses, tissue edema, or torn muscle fibers and/or connective tissue damage.
• DOMS is important for stimulating muscle hypertrophy, thus potentially important to maximize the training response.

Exercise-Associated Muscle Cramps (EAMCs)

• Often occur during or after exercise, or during the night.
• Usually occur due to electrolyte imbalances, especially during high rates of sweating, or from sustained motor neuron activity resulting from muscle spindle activity and decreased Golgi tendon organ activity.

Muscle Soreness and Muscle Cramps: Causes and Occurrences

• Causes of muscle soreness and cramps include accumulation of metabolic waste, tissue edema, eccentric muscle actions during training, structural damage to muscles, inflammatory reactions, sustained motor neuron activity, and muscle fatigue.

Designing Resistance Training Programs: Review

• Consider different dynamic training programs. Perform a training needs analysis. Select appropriate resistance levels. Decide whether to use single or multiple sets. Create a training program using periodization. Assign specific forms of resistance training based on the sport or goals.

Did You Know...?

• Resistance training benefits almost everyone, regardless of gender, age, athletic involvement, or sport.

High resistance strength training in elderly.

• High resistance strength training programs can effectively increase the knee extensor strength in older individuals. 8 weeks of training can increase strength by more than 150% and maintain this strength increase. Retraining after detraining (i.e., after a break) resulted in a 32% decrease in knee extensor strength but took several weeks before returning to original levels.

Test your knowledge on the principles of resistance training and muscle soreness. This quiz covers topics including delayed onset muscle soreness (DOMS), strength measurement, and program design considerations. Perfect for students and enthusiasts of exercise science.