by Yuri VerkhoshanshyEdited by Jim O’MalleyEditor's note : Professor Verkhoshansky is widelyrecognized as the world's foremost authority onspeed-strength training.IntroductionThe author conducted a study regarding thecomposition and structure of the capacities thatgenerate explosive movements, depending on thefollowing variables :*the type of sport*the participant's age, sex, and length of sportingcareer*the type of muscle contraction, the type of resistanceand the level of resistance*the composition and number of body componentsactively involved in the performance of the exerciseI took into account that dynamic and isometriccontractions do not exhaust all of the varieties that arepossible in an approach to conditioning training - inparticular the so called "combined regimen" in whichthe contraction is preceded by mechanical stretchingof the muscles, a widely spread system in the trainingof many sports. When a "combined regimen" isoperative, the elastic potential of mechanical musclestretching provides an extra source of energy whichenhances the subsequent muscular contraction.A muscles ability to switch rapidly from a yielding(eccentric) contraction to an overcoming (concentric)contraction by using elastic potential (accumulatedduring stretching) to increase the muscular contractionis commonly known as the neuromuscular systems"reactive capability".Finally, the speed-strength characteristics incontrolled tasks involving overcoming (concentric) andcombined (eccentric-concentric) muscle contractionsappear to be closely interrelated. the overcoming(concentric) contraction is a sufficiently informativeindicator of the capacity of the neuromuscular systemto generate explosive force.Explosive Force CapabilitiesThe capacities that influence explosive forceapplications include :* the maximal isometric muscle strength, asdetermined by isometric tension with no time limit* the maximal muscle strength, as displayed duringexplosive efforts in either isometric or dynamicperformance. In the case of dynamic work, one shouldconsider the level of resistance (which affects thespecific strength displayed) and distinguish betweenmuscular strength exerted against light, medium, andheavy resistance.* explosive muscular strength, as an indicator of thecapacity to rapidly generate a maximal effort during anisometric contraction* explosive maximal strength as an indicator of thecapacity to rapidly generate a maximal effort during adynamic contraction* starting muscular strength, as an indicator of thespeed at which force is generated at the start of amuscular contraction. It applies to both isometric anddynamic contractions.* accelerating muscular strength, as an indicator of thespeed with which force is developed during the initialmotion of a movable object.This group of component capacities appears intasks involving explosive muscular force,independent of an athlete's specific sport, age,training age, and the type of muscular contraction. Thecapacities are also independent of the level ofresistance, the functional specialization of individualmuscles and the composition and number of bodysegments involved in an exercise.Predominant FactorsThe predominant role of one factor or another inproducing explosive force depends on the level ofresistance to be overcome in a particular exercise. Incase of a light resistance, or during the initial speed ofa movable mass, the absolute contraction speed andthe starting muscular strength are of primaryimportance.As resistance increases, the explosive, dynamic,and accelerating muscular strength becomes moreimportant. On the other hand, maximal isometric andexplosive isometric muscular strength play a majorrole in the so called "starting movements" that areexecuted against heavy resistance.The characteristics of the general ability to generateexplosive force in dynamically or isometrically workingmuscles are, as a rule, the first factors involved inspeed-strength development exercises. However, inregard to the factorial analysis of speed-strengthcharacteristics involved in ankle extension, it is thestarting muscular strength that becomes the numberone factor. This is the possible result of the anklesspecific role in sporting activities because a powerfulexplosive effort is required of the ankle and foot invirtually all sports.The limited range of movement in the ankle joint,which results from the functional specialization of therespective muscle groups, demands the developmentof starting strength in the muscle groups and theability to generate instantly effective force in a limitedrange of movement. Starting muscular strength isevaluated in isometric and dynamic performances.However, it must be kept in mind the isometric startingstrength is a different factor from dynamic startingstrength.According to Zatsiorsky and Verkhoshansky thecapacity to generate maximal force in isometric anddynamic performances is generated by differentneuromuscular mechanisms. The mechanisms arerelatively independent of each other in their functionaldisplay and development.In dynamic contractions performed using freeweights, the muscle contracts isometrically before themovement starts. As soon as the muscular forceequals the amount of resistance and the movementbegins, the muscle begins to contract dynamically.Resistance LevelsResearch data in the study of the composition andstructure to generate explosive strength revealed, asexpected, that the role of strength capacities whenusing explosive force depends on the amount ofresistance to overcome. There is a link between theresistance and the capacity to rapidly generatemovement against resistance. Consequently, strengthincreases as the amount of resistance grows. Themaximal factorial weights of the speed characteristicscorresponds to the optimal levels of resistance.Strength capacities can be differentiated within therange of resistances. This fact leads to theclassification of power zones in the manifestation ofexplosive capacities and allows us to differentiatemuscular force in correlation with the power zones. Asthe resistance increases, there are increases inperformance, influenced by other factors, such as theathlete's training age, body size, strength potential andexplosive and accelerating muscular strength.While the factorial composition of speed-strengthcharacteristics for high performance and elite athletesappeared to be quite clear, the same cannot be saidfro athletes in lower performance categories. Ourstudies indicated imbalances in the composition andstructure of the capacities that generate explosiveforce in the first stages of systematic training. Thisoccurs because of an uneven development of specificcapacities, the absence of a clear cut training system,poor developmental sequences, and so on.It is during the advanced stages of proficiency, whenthe content of training becomes clear cut and specific,that the composition and structure of the capacitiesresponsible for generating explosive force becomeclearly distinguished. Consequently, it is important toemphasize specific physical development as soon asan athlete has finished the all-around generaldevelopmental stage.Effective ImprovementOur study also revealed that the capacitiesdiscussed above are not of equal value in generatingexplosive force. Depending on the requisites ofaccomplishing a given motor performance task, onecapacity or another assumes the primary role andtherefore contains the primary potential forimprovement.In an integrated motor performance the individualcapacities, which produce their neuromuscularmechanisms relatively independently, interact in anorderly manner to accomplish the common task. At thesame time, they preserve their individuality andreadiness to enter into any functional combination thatmay be required under the changing conditions of theperformed activity.It is interesting to note that our research resultsfailed to corroborate the frequently expressedsupposition that the ability to generate explosiveefforts is a synthesis. That is , a product ofqualitatively blending diverse capacities, such asspeed and strength, which were developed separately.Only a regimen that virtually duplicates the speedstrengthprimary requirements of an event can provideeffective improvement. Most importantly, it should bekept in mind that the necessary functional interactionbetween the specific neuromuscular mechanismsrequired in a specific task are decisive. No otherregimes or combination of regimes are an effectivesubstitute.