TIME UNDER TENSION..The actual MUSCLE STRESS to build.

STRESSING THE MUSCLE.

THE PIKE PUSHUP

I just started doing these during my shoulder routine. They are AMAZING! To keep the pressure off my back and hips. These work great!

Many experts argue that in order for an adaptation and super compensation to occur in the muscles, a greater effort must be exerted with overloads than is usually performed. In a program that involves constant overload, the physiological systems continue to adapt to the stress imposed by the exercise. Also for this reason it is believed that experienced athletes have a greater need to train at higher intensities (80% 1RM) than beginners (60% 1RM) to maximize strength and hypertrophy gains .This means that a certain amount of stress must be produced that the physiological system adapts to improve. In any case, according to more elaborate training theories, making only load increases without altering other variables is limiting, since it is not only this that must be manipulated, but also the Time Under Tension and the relative speed of the movement phases. . In these terms, some cycles could foresee a protocol with a lower intensity and load but with a longer time under tension to bring new adaptations, and further developments of strength and hypertrophy , while not necessarily and completely applying the concept of a chronic and progressive increase of the loads only. The principle of progressive overloading fact it foresees that not only or necessarily the loads are progressively increased over time, but also other variables such as the Time Under Tension, which variation can be determined by the alteration of the repetitions alone, by the alteration of the movement speed during the same ( speed of movement ), or by the application of special techniques that require an increase. 

Repetition range 

In physical activities with weights ( Resistance training ), there are common standards that recognize a specific goal in the number of repetitions performed during the series: 

• between 1 and 8 maximum repetitions (80-100% 1-RM ) a greater development of maximum strength is stimulated ;
• between 8 and 15 maximum repetitions (65-80% 1-RM  ) the development of muscle hypertrophy is mainly stimulated ;
• more than 15 repetitions (<65% 1-RM  ) essentially improve muscle endurance skills ;

However, the number of repetitions is not the only aspect to consider in order to obtain a certain type of muscle stimulus, but is presented only as one of several benchmarks for developing the improvement of particular skills. The specific repetition ranges mentioned above are often used to give a reference on the type of overload that is indicatively best suited to a certain type of stimulus, as most commonly occurs for the development of strength, muscle hypertrophy or muscle endurance. This method, however, turns out to be incomplete in groped for certain results. It is necessary to take into account not only the range of repetitions, but also give importance to the execution time of the movement during a set, a concept recognized as time under tension of active skeletal muscle, more commonly known as Time Under Tension or TUT. TUT is the total time the muscle is placed under stress (tension) during any movement, and implies the physiological principle that muscles must be kept under tension for a certain period of time to stimulate, for example, strength gains and hypertrophy.

So just following the relative range of repetitions, such as those suitable for hypertrophy, does not actually say enough about the type of stimulus you are looking for. This happens because this stimulus is not only dependent on the repetition range and intensity, but also on the activity time, a figure which, together with the relative intensity (% 1RM), suggests the prevailing energy system and the relative substrates used. . In fact, a defined maximum number of repetitions or RM (for example 10), can be completed within 15 seconds (the action time of the anaerobic Alactacid system and the phosphates) to stimulate the main development of strength or power, in 30 seconds (the time of action of the anaerobic lactic acid and glycogen system) to develop mainly hypertrophy, muscle endurance . Obviously, if this maximum number of repetitions is performed within a very short time, it will be possible to use much more load, while with very prolonged TUTs, the load will have to undergo a decrease due to the long duration of the effort. Therefore, even with the same maximum repetitions (RM), a very different stimulus can be induced based on various factors, such as the intensity of the load (% 1-RM) or the speed of movement. This naturally also affects the type of fiber recruited, since the execution of a series with very short TUT (10-15 sec) and a very high intensity (85-90% 1RM) will determine the maximum recruitment of fibers ( white or rapid) with the synergistic intervention of fibers and I, while lower intensities determine a lower recruitment of fibers . Usually, series of 10 repetitions (10 RM) on average are indicated to stimulate hypertrophy and one of the reasons can be explained by the fact that this rep range is low enough to allow the muscles to lift adequately heavy loads, and a sufficient number of repetitions to allow the muscle to withstand a long enough TUT with heavy loads. But still it must be taken into account that if these 10 repetitions are completed in very short TUT, such as 15 seconds, a great muscular tension is not created and an optimal triggering of all those physiological processes that are considered most adequate to create muscular hypertrophy. The range of repetitions relating to a given stimulus have been developed because theoretically they should correspond to a given time under tension. 

TUT and recruitment of muscle fibers 

A sufficient amount of muscle tension is required to cause physiological adaptations with weight training. This type of exercise also involves training the nervous system to recruit motor units. A motor unit comprises a motor neuron with all the muscle fibers it innervates. The principle of the size ( size principle ), it indicates that the motor units are for the most part recruited in order of increasing size from the smallest (type 1) to the larger (type 2b), since the size (diameter) of the group of units motor skills is directly related to its ability to produce force . A lighter demand for force (and intensity) towards the muscle will place emphasis on the activation of the slow twitch type I fibers. As the strength required of the muscles increases, type IIa intermediate fibers are activated with the help of type I fibers. With more demanding muscle strength demands, the more powerful (and larger) type IIb fibers intervene, with support. of type I and type IIa fibers .

There are 2 main categories of muscle fibers, type I and type II:

• the type I fibers are referred to as slow-twitch fibers or red. These fibers contract slowly and fatigue more . These are the fibers mainly used when lifting light loads and prolonged efforts;
• the type II fibers are referred to as fast or white contraction. These over contract very quickly but also tire very quickly, and are used for quick, short, and higher intensity efforts;

Fast twitch fibers can be divided into types IIa and IIb:

• the type IIa fibers are moderately fatigued and have hybrid properties of both the fiber type I and that of those of type IIb;
• the fibers of type IIb easily fatigued and are recruited for short and very intense efforts, such as lifting heavy weights, the sprint or the jump ;

Not surprisingly, weight lifters (weightlifting), and power lifters ( power lifting), that is athletes who perform their performance through the Alacticacid system (or phosphates), higher intensities (> 90% 1RM), and TUT shortened (usually less than 20 seconds), show increased type 2 (rapid) fiber hypertrophy, while body builders (bodybuilding) appear to show hypertrophy in both type 2 and type 1 fibers , probably also due to the execution at wider and more variable intensity and TUT.

Type 1 fibers are recruited from 0 to approximately 60% 1-RM. Around 20% 1-RM some type 2a fibers are recruited, but their maximum recruitment occurs at about 75-80% 1-RM. Type 2b fibers do not begin to be recruited until approximately 60-65% 1-RM, and continue to be recruited until approximately 85% 1-RM . Therefore, the maximum recruitment of motor units is obtained when type IIb fibers are also involved, which intervene last, starting from moderate loads up to very high loads . Type IIb fibers are about 50% more hypertrophied than type 1 fibers however their maximum recruitment occurs with a load relative to approximately 85% of 1-RM (i.e. 4-5 RM), an intensity necessary to recruit the greatest number of motor units, as well as develop greater strength gains , and this is allowed by a type of training protocol with such a number of sets and repetitions. But this method correlates with a rather short TUT, which activity times are characteristic of the anaerobic Alactacid or phosphate system. Type 2b fiber (white fiber) is less involved at lower intensities, but this intensity does not lead to significant hypertrophy of type 1 (red) fiber. The question of the maximum recruitment of motor units in relation to the load (intensity) finds evident correlations with the TUT, as the intensity (% -1RM) is inversely proportional to the TUT. Consequently, shorter TUTs in relation to repetitions at maximum fatigue (RM) are associated with higher motor unit recruitment up to 85% 1-RM  . But TUT of longer duration (usually connected but not necessarily with higher repetitions) lead to a more significant intervention of the type 1 and type 2a fibers, affecting a selective hypertrophy of the same.

Sometimes the scientific literature recognizes that higher load intensities are suitable and necessary for advanced athletes , and that these intensities can correspond to 85-90% of 1RM . Also in this case it may follow that, to stimulate almost selectively the different types of fibers and further gains in volume and strength, it may be advisable to perform cyclical variations of the TUT connected to the different speed of movement, different repetition range, different load, and different relative intensity.