Resistance Training for Age-Related Physical Declines

Before implementing countermeasures, specific issues must be identified through assessment
- Sarcopenia: Identified through methods such as DEXA (Dual-energy X-ray absorptiometry) scans to measure muscle mass.
- Dynapenia: Identified through hand grip strength tests or various forms of dynamic testing.
- Powerpenia: Identified through specific power tests to measure the rate of work.

Resistance training (RT) is a well-established method for increasing muscle mass, strength, and power in both athletic and older populations.
Fiber Type Shifts: Exposure to RT can cause shifts in muscle fiber types, specifically moving hybrid fibers from type $2X$ to type $2A$ to facilitate the production of high levels of force.
Muscle Mass Maintenance: RT increases muscle size and mass to offset age-related declines and the associated risk of physical inactivity.
Neuromuscular Integrity: RT helps mitigate motor unit integrity issues, including:
- Denervation.
- Reduction in motor unit capacity.
- Reduction in motor unit availability.
Resilience and Muscle Quality: By increasing muscle quality, RT improves an individual's resilience and ability to tolerate the fatiguing effects of training and activities of daily living (ADLs).
Physical Capacity: Improved strength and power lead to better mobility and overall fitness.

A significant portion of the Australian population does not engage in sufficient resistance training.
$5.2\%$ of Australians engage in sufficient amounts of RT (defined as more than $3$ sessions per week or meeting specific activity thresholds).
Approximately $15\%$ of Australians engage in some RT, but the amount is insufficient to achieve physical performance improvements.
The majority of Australians engage in no resistance training at all, leading to a trajectory of:
- Decreased muscle mass, strength, and power.
- Increased disease states.
- Decreased physical activity, motivation, and mobility.

General recommendations are provided by organizations such as Exercise and Sports Science Australia (ESSA) and the British Association of Sport and Exercise Sciences (BASES) (including the new chartered version).
ACSM (American College of Sports Medicine) Guidelines:
- Frequency: $2 \text{ to } 3$ days per week.
- Exercise Selection: $8 \text{ to } 10$ exercises involving major muscle groups (lower body, upper body pressing, upper body pulling, bicep curls, leg extensions, etc.).
- Volume (Healthy Adults): Single sets of $8 \text{ to } 12$ repetitions.
- Volume (Older Adults): Single sets of $10 \text{ to } 15$ repetitions may be effective.
Critiques of ACSM Guidelines:
- Lack of specific prescription for progressive overload, which is essential for adaptation beyond the initial $6 \text{ to } 12$ week period.
- The single-set approach may not provide a sufficient training stimulus for long-term goals.
- The single-set of $10 \text{ to } 15$ RM provides a moderate dose but may not meet the overall ACSM goal of $150 \text{ to } 200$ milligrams of vigorous exercise per week or the expenditure of $150 \text{ to } 200\,kilocalories$ per training bout.

NSCA (National Strength and Conditioning Association) Guidelines offer additional tweaks:
- Volume: Recommends more than one set, typically $2 \text{ to } 3$ sets for advanced individuals.
- Intensity/Repetition Ranges: Using $6 \text{ to } 12$ repetitions for muscular strength to target the neural components of force production and mitigate dynapenia.
- Equipment: Suggests starting beginners or mobility-restricted individuals on machines and progressing to free weights.
- Power Training: Includes high-velocity training components to develop power, which is a critical factor in all-cause mortality.
- Dynamic Correspondence: Exercises should mimic tasks of daily living to improve functional capacity.

A $2019$ study compared modified versions of NSCA and ACSM guidelines (both using $3$ sets) in older female adults:
- Strength (Lower Body): Both sets of recommendations resulted in similar strength increases.
- Strength (Upper Body): The ACSM guidelines ( $3$ sets of $10 \text{ to } 15$ reps) resulted in greater strength improvements than the NSCA recommendation ( $3$ sets of $8 \text{ to } 12$ reps) due to higher volume.
- Functional Performance: No difference between groups; both improved walking/gait speed and chair-stand performance (repetitions in $30\,seconds$ ).
- Muscle Mass: The higher volume ( $3$ sets of $10 \text{ to } 15$ RM) resulted in significantly greater increases in skeletal muscle mass compared to the $8 \text{ to } 12$ rep group.

Professor Newton (2002) conducted a $10$ -week training program involving older men (in their $60s$ ) and younger adults (in their $20s$ ).
Programming Model: Daily Undulating Periodization (DUP) performed $3$ days per week.
- Hypertrophy Day: $3 \text{ to } 6$ sets of $8 \text{ to } 10$ reps (Squat and Leg Extension).
- Strength Day: $3 \text{ to } 6$ sets of $3 \text{ to } 5$ reps (Squat and Leg Extension).
- Power Day: $6 \text{ to } 8$ repetitions with a lighter load performed as fast as possible (Squat and Leg Extension).
Findings:
- Younger adults have a higher absolute capacity for rapid force expression and more type $2$ fibers.
- Older adults still showed significant increases in the capacity to rapidly express force.
- There was no difference between younger and older adults in the magnitude of change for power output in the squat jump with external loads.
- Specific power training is vital for offsetting age-related declines in the rate of work and reducing all-cause mortality.

It is critical to start resistance training early in life (youth and adolescence) rather than only using it to mitigate existing declines.
Building Reserves: Establishing high levels of strength and muscle mass during younger years creates a "reserve."
Starting from a higher baseline means that even as age-related declines occur, the individual remains at a higher functional level compared to someone who started with a low baseline in childhood.
Developing training habits early helps reduce the overall impact of sarcopenia, dynapenia, and powerpenia later in life.