Why Do Muscles Know Tension?

Many lifters, trainers, and coaches believe that "muscles only know tension." This view is overly simplistic. In reality, a number of factors must be taken into account. What degree of tension? What duration of tension? What frequency of tension? What kind of tension? Certainly passive tension isn't as effective as active tension in packing on lean mass.
Many believe that the continuous quest for increased maximal strength is the key to developing massive muscles. But while increased strength is definitely related to increased muscle cross sectional area (CSA), there are multiple adaptations that can boost strength without increasing muscle hypertrophy (Schoenfeld, 2010).
In Neuromechanics of Human Movement, Roger Enoka (Enoka, 2008) lists
eight potential neurological areas for non-hypertrophy related strength gains:
? Enhanced output from supraspinal centers as suggested by findings with imagined contractions
? Reduced coactivation of antagonist muscles
? Greater activation of agonist and synergist muscles
? Enhanced coupling of spinal interneurons that produces cross-education
? Changes in descending drive that reduce the bilateral deficit
? Shared input to motor neurons that increases motor unit synchronization
? Greater muscle activation (EMG)
? Heightened excitability and altered connections into motor neurons
Of all of these adaptations, basic coordination between the muscles is the single greatest contributor to non-hypertrophy related strength gains.
Along with neurological adaptations, adaptations involving increased stiffness in the tissues that connect from bone to bone (including tendons, extracellular matrix, etc.) can lead to increased force transmission from muscle to bone, and play a significant role in increased strength gains.
Pennation angle. The angle formed by the individual muscle fibers with a muscle's line of action significantly impacts strength irrespective of muscle hypertrophy. Specifically, increased pennation angles appear to have a negative correlation with muscle strength - as pennation angle increases, a muscle's force-generating capacity decreases (Kawakami et al. 1995). Interestingly, studies show that bodybuilders have greater pennation angles than power lifters, potentially due to their training methods (Ikegawa et al. 2008).
Similarly, there are multiple ways in which muscles can grow larger without significantly affecting maximal strength. One such way this can occur is by an increase in non-contractile elements in the muscle cell. Non-contractile hypertrophy includes increases in collagen, glycogen, and other cellular subunits, a phenomenon commonly referred to as "sarcoplasmic hypertrophy" (Siff and Verkhoshansky,
1999).
Since force production is generated by the sarcomeres, sarcoplasmic hypertrophy will have no effect on your 1RM.
However, the increased bulk provided by the non-contractile elements will nevertheless produce a tangible impact on muscle size.
An increase in the size of slow-twitch Type I fibers can also affect hypertrophy without having much effect on maximal muscular strength. Type I fibers are endurance-oriented fibers that have limited ability to produce high levels of force (McCardle et al. 2010). However, contrary to what some believe, Type I fibers do increase in size when subjected to a resistance training stimulus, although their hypertrophic capacity is about 50% less than that of fast twitch fibers (Kosek et al. 2006; Staron et al. 1989).
Interestingly, bodybuilders have been shown to have a greater Type 1 cross-sectional area than powerlifters (Tesch and Larsson, 1982). This may well help to explain why Tom Platz displayed greater muscular endurance than Fred Hatfield but wasn't as strong on an absolute basis.
If maximum strength were the end-all-be-all for muscular hypertrophy then powerlifters would be the biggest human beings on the planet, and bodybuilders would employ maximal singles instead of chasing the pump. Simply put, stronger does not necessarily equal bigger, and bigger does not necessarily equal
stronger.