The increased muscle mass obtained after 12 weeks of continuous resistance training will provide more receptor sites for insulin uptake, further increasing insulin sensitivity. Assuming a major decrease in fat mass, in part due to increased BMR from the added muscle, insulin sensitivity would increase even more due to the smaller-sized fat cells eliciting a lesser insulin resistant effect compared to when they were larger (more dense). A significant increase in bone mass will have accumulated compared to pre-training. The increased resting levels of testosterone will act towards preventing osteoporosis. (more…)
After 4 weeks there won’t be much of a change in body composition. Taking into account the caloric expenditure of exercise and assuming a low-fat diet including high-glycemic index carbohydrates is followed, there will be a slight decrease in fat mass. There will be no noticeable increase in muscle mass. Mostly all the strength gains at this point will be due to neuromuscular adaptations. Bone density will have increased due to the effects of increased testosterone and increased osteogenic activity. (more…)
A single bout of resistance training can lower blood sugar to hypoglycemic levels in normal, healthy individuals. For diabetics this naturally occurring mechanism is especially beneficial in acting towards down regulation of blood glucose, as this effect can last up to several days. Improved glucose removal and metabolism may last for several hours and possibly up to a couple days after an exercise session. 7 (more…)
Resistance training for muscle hypertrophy involves working at 55-80% of 1RM using a high volume of exercises with 3-6 sets, 8-15 reps each, and a 30-90 second rest between sets.
Training for muscle strength involves working at 70-95% of 1RM using a moderate volume of exercises with 3-6 sets, 3-6 reps each, and a 2-3 minute rest between sets.
Training for muscle power involves working at 70-100% of 1RM using a low-moderate volume of exercises with 4-8 sets, 2-5 reps each, and a rest period of 3-5 minutes.
Lastly, training for muscle endurance involves working at up to 65% of 1RM with at least two sets, 20 reps each, and a 30 second or less rest between sets.
Training primarily for muscle growth involves recruiting as many muscle fibers as possible to induce hypertrophy of the entire muscle group. The short rest periods are used to not allow all the previous muscle fibers to recover so that new muscle fibers can be activated. Strength training uses long rest periods since muscle hypertrophy is not the main concern.
This type of training relies on the neuromuscular adaptation of recruiting very large motor units at once to produce high amounts of force. Training for muscle power involves high velocity contractions to increase power output. The rest periods here are longest since power movements need all the muscle fibers involved to be fully rested.
Training for muscular endurance involves high repetitions at low intensity so that the aerobic, slow twitch fibers are being worked. The short rest periods are used to prevent the muscles from being able to use anaerobic glycolysis for energy and to depend on aerobic metabolism.
Specific neuromuscular adaptations are determined by the type of training program followed. The four main training programs pertain to muscular hypertrophy, muscular strength, muscular power, and muscular endurance.
Hypertrophy of muscle is a result of an increase in the cross-sectional area (CSA) of the muscle’s individual fibers. An increase in the muscle fibers myofibrils and actin and myosin filaments increases muscle’s CSA. As a result of increasing these muscle fiber components, more cross-bridges are formed which leads to an increase in muscular strength. Type II a muscle fibers are the most responsive fiber type to strength training. An increase in the angle of pennation of a muscle also is an adaptation of muscle hypertrophy. Muscle hypertrophy contributes very little or not at all to strength gains during the beginning of a resistance training program; however, it becomes the most important contributor to increases in strength after about 10 weeks of training.
Muscular strength refers to the highest amount of force that a muscle can produce. An increase in strength does not always result from a concurrent increase in muscle hypertrophy. Furthermore, studies have shown that muscular strength can increase without an increase in muscle size. It is the neural adaptations to resistance training that are always responsible, fully or in part, for gains in muscular strength. An increase in recruitment of large, high threshold motor units and synchronization of motor units will increase strength. When motor units are more in synch muscle contraction is made easier and muscles are able to generate more force.
Another neuromuscular adaptation to muscle strength involves inhibition of the Golgi tendon organs (GTO’s). GTO’s play a role in preventing connective tissue injury by stopping muscle from producing more force than the surrounding tissue can handle. This process is called autogenic inhibition. However, resistance training can eventually prevent or decrease the inhibitory effect, which would lead increases in strength. Inhibition of antagonistic muscle groups is a neuromuscular adaptation that can also result in strength gains. This type of inhibition involves reducing the opposing force produced by antagonistic muscles when the agonist group is concentrically contracting, leading to increased muscular strength.
Muscle power involves strength and the speed of movement of muscle. Power is more important than strength alone in most sports. High-speed training such as plyometrics is used to increase power. The neuromuscular adaptations to this type of training result in recruitment of larger, fast-twitch motor units and motor units firing at a very high rate. Also, motor unit synchronization can increase strength, which could lead to power gains.
Muscular endurance involves the maintenance of repeated muscle actions. It can be increased via increased muscular strength and metabolic changes. These changes involve increased mitochondrial density of a muscle and increased capillary density. Smaller, slow twitch motor units are the most active in activities involving muscular endurance.
