Muscle Adaptations to Plyometric vs. Resistance Training in Untrained Young Men

Muscle Adaptations to Plyometric vs. Resistance Training in Untrained Young Men

Conventional resistance training (CRT) has shown to increase neural input to agonist muscles with some apparent decrease in antagonist co-activator. In regards to plyometric training (PT), this form of training generally relies on the phenomenon know as the stretch-shortening cycle (SSC). This occurs when a rapid eccentric muscle action facilitates an increase in force and power output during a succeeding rapid concentric contraction phase. The aim of the current investigation hoped to compare possible changes in muscle strength, power and morphology through CRT vs. PT. Additionally, examination into adaptations analyzed single-fiber and whole muscle structure and the overall changes in maximal strength and power.

Beginning with subject requirements, the researchersselected young men with no prior history of strength training and were not previously involved with sport activities involving SSC patterns. This criterion was appropriate to more distinctly assess neurological and structural changes, which may not have be efficiently presented in trained populations. In addition to participant selection, examining 12 weeks of training allowed for sufficient assessment into varying dominant adaptations. Exercise protocols were constructed within theoretical rep and set ranges, in a progressive model to inhibit any plateaus during the regiments.

When evaluating testing protocols, assessments were completed two days apart for adequate recovery, to minimize any confounding fatigue. Ultimately 15 subjects were analyzed, showing significant increase in 1RM Leg press and 3RM Knee Extension for both groups. Though not surprising, only the PT group demonstrated a significant increase in CMJ Height and Power and a significant difference when performing the Ballistic Leg Press, favoring PT. When examining 1RM Hamstring Curl, there was a significant difference between groups when comparing total load, favoring CRT. This performance measure is currently lacking evidence and is suggested that further investigation is required. With greater investigation, maximal hamstring strength may lend greater insight into the mechanisms associated with strength and/or power.

Secondly, muscle fiber and whole muscle CSA was assed post exercise. An overall training effect was demonstrated in both groups, but no significant differences were present for regional and whole muscle CSA. Type IIA presented a training effect but surprisingly almost no difference in the PT group, resulting in a relatively strong trend favoring CRT. Though presenting no difference in either group for Type IIX, MCH-IIX in both groups decreased but no change in Type I/IIA.

This investigation lends great evidence into the proposed adaptations in these differing training protocols. Similar to thehypothesis, CRT would demonstrate greater hypertrophic responses and PT would favor power adaptations. Few studies have examined hamstring strength in CRT, which is required due to an estimated 45% deficit in hamstring strength experienced with PT. Suspected limitations may be seen in minimal subject variability, permitting studies with a larger number of participants. Which may assist in analyzing a greater effect in CMJ performance, which has been used as a gold standard for power adaptations.