Muscle proteins exist in a dynamic equilibrium between rates of synthesis and breakdown. Age-related muscle wasting (sarcopenia) is caused by elevated basal rates of breakdown and reduced sensitivity to anabolic stimuli such as protein ingestion and resistance exercise. Consuming dietary protein in close temporal proximity to resistance exercise increases the stimulatory effect of protein on muscle protein synthesis, potentially helping offset age-related anabolic resistance.
Strength training is the foundation of any good exercise program. It helps to build and maintain muscle mass, burns calories at rest, and helps prevent bone loss as you age. Most beginners experience a quick increase in strength and body composition when starting a resistance training program, but after about 14 weeks most see little or no further gains in muscle size (a plateau). This is due to a process called neural adaptation. The nerves servicing the muscle start firing more frequently and more motor units to initiate the contraction – this increases your strength, but it does not result in larger building muscle.
To continue seeing gains, you need to keep challenging your muscles with new stimuli. This is done by gradually increasing the weight, number of reps or sets, or type of exercise you do. When deciding on these variables, consider consulting with a certified fitness trainer or coach to ensure proper technique and safety.
Cardio exercises like running, swimming, and cycling boost your endurance and improve the function of the heart, lungs, and blood circulation. They also burn calories, especially if you do high-intensity interval training (HIIT). HIIT involves going all-out for 30 seconds followed by four minutes of rest for a total of four to six cycles. Using low resistance, you can work out your entire body this time, including your muscles, joints, and core.
While HIIT increases insulin sensitivity, it does so via a different pathway than resistance training. However, the combination of resistance and HIIT may result in better insulin sensitivity than either alone. Interestingly, it has been shown that lower load resistance training is equally effective at promoting muscle anabolic signaling than higher loads.
A diet high in protein is key for building muscle. Protein is the main building block of muscles, and it helps to repair and build new muscle tissue after a workout. Protein is also an important nutrient for those who want to lose weight. The anabolic response to resistance exercise and dietary protein is highly sensitive and regulated, as demonstrated by day-to-day changes in muscle net protein balance (MPS minus MPB). Consuming large dietary protein boluses after exercise is necessary to stimulate MPS sufficiently to shift net protein balance in favor of muscle gain.
Interestingly, critically ill patients have a blunted response to intraduodenal protein feeding, which is associated with lower protein synthesis and higher protein turnover. This suggests that altered muscle protein metabolism, rather than reduced physical activity per se, maybe the underlying mechanism for anabolic resistance in the context of critical illness. Supplementing with BCAA and leucine can mitigate anabolic resistance, as they are the two amino acids that stimulate MPS. Moreover, research shows that older adults need twice as much leucine compared to younger people to activate the motor signaling pathway, which in turn triggers protein synthesis.
Studies have shown that getting enough sleep is essential for muscle recovery and growth. A good night’s rest helps the body restore glycogen levels, ensuring muscles have enough fuel for exercise, and also releases hormones that are important for muscle recovery. Among these is testosterone, which promotes muscle growth and repair. One study found that individuals who slept just 5.5 hours per night had less myofibrillar protein synthesis than a group that slept 8.5 hours. This could lead to a loss of muscle mass over time.
The good news is that physical exercise, and specifically resistance exercise (RE), can prevent or overturn the deleterious effects of sleep debt on skeletal muscle. This is because RE stimulates a positive hormonal response in the muscles and endocrine system that can counteract the negative effects of sleep deprivation. This non-pharmacological strategy has many health benefits and is feasible for the general population, with very few contraindications. Moreover, RE is inexpensive and widely practiced, making it an important tool in public health.
The underlying mechanisms of muscle-building anabolic resistance are complex. However, it appears that a reduction in basal rates of protein synthesis and a decrease in free circulating amino acids impair the ability of muscles to respond to normal robust anabolic stimuli such as dietary proteins and resistance exercise.