1

THE APPLICATION OF COMPLEX TRAINING FOR THE DEVELOPMENT OF

EXPLOSIVE POWER

Brad McGregor (MSptSc

Abstract

The ever-increasing emphasis that is placed on athleticism and sporting success

has led scientists to investigate numerous training methods that can have a

positive effect on performance. One such method that has received significant

attention is complex training (CT).

This method of alternating heavy and light resistances has the end goal of

improving power output. In their recent review of complex training Docherty et al.

(6) credit Verhoshansky with early work in this field as far back as 1973. Although

this was one of the first publications on the topic, one suspects that the Soviets

(and possibly other eastern bloc countries) may have been using complex

loading as a training tool for some time.

Researchers that have found CT to be beneficial credit a post-activation

potentiation (PAP) as the major physiological factor. Docherty et al. (6) explain

that the explosive capability of a muscle is enhanced after it has undergone

maximal (or near maximal) contractions.

Although some studies have not found any benefit from performing this type of

training, the majority of research has supported it’s application as a tool to

enhance expression of muscular power and explosiveness. However as with

most relatively new training techniques, there is a need for more long-term

studies. More work also needs to be done to determine the optimal combination

of training variables for different sports and those with varying training ages.

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Definitions of CT

There is still some debate on exactly what constitutes CT. Fleck and Konter (11)

quoted Verhoshansky’s simplistic definition as a series of exercises formed in

succession with a goal of improving one physical characteristic. He went on to

say that these exercises where designed to improve “explosiveness.” Examples

of Verhoshansky’s complexes include:

Back squats with depth jumps

Kettle bell jumps with standing long jumps

Push off and knee lift with 30m sprints.

Ebben and Watts (10) completed a review of literature on CT in 1998 and

expanded on Verhoshansky’s explanation. They defined CT as alternating

“biomechanically comparable high-load weight training and plyometric exercises

in the same workout” (p 18). The example of CT cited in this study was bench

press and medicine ball power drop. Interestingly, the same authors state that at

the time only one study had examined CT although it was widely practiced.

In 2002 Duthie et al. (7) described CT as “various sets of groups/complexes of

exercises performed in a manner in which several sets of a heavy resistance

exercise are followed by sets of a lighter resistance exercise” (p 530). These

authors also mention the term “contrast loading” and define this as “the use of

exercises of contrasting loads, that is, alternating heavy and light exercises set

for set” (p 530). Of all the articles referenced in the current review, this was the

only paper to mention contrast loading suggesting that more research needs to

be done comparing these two training methods. It is possible that some authors

may have indeed been investigating contrast training while referring to it as CT.

Docherty et al. (6) define CT similarly to Ebben and Watts (10) as “the execution

of a resistance-training exercise using a heavy load (1-5RM) followed relatively

quickly by the execution of a biomechanically similar plyometric exercise” (p 52).

According to Duthie et al. (7) this definition is referring to contrast training!

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In recent times it appears as though the invent of contrast training is the source

of some confusion amoung scientists investigating the CT phenomenon. As

further research is conducted this issue will no doubt be clarified.

Physiology

Verhoshansky is acknowledged throughout the literature as being one of the first

authors to publish on CT. In 1986 a paper written by Fleck and Konter (11)

outline Verhoshansky’s explanation of the CT phenomenon:

“Professor Verhoshansky used the example of the perception of lifting a half-full

can of water when you think it’s full. The excitability of the central nervous system

responds in such a way that the water literally flies in the air because of the force

applied. It is because if the body thinks it has to do more heavy work, so it

remembers what is necessary to lift the full can and reacts accordingly” (p 66).

This “fooling” of the nervous system has been expanded upon in recent times to

offer 2 proposed mechanisms for post activation potentiation (PAP). Docherty et

al. (6) explain the first of these theories as enhanced “motor-neuron pool

excitability” (p 53). Specifically, a greater neural effect is the result of any/all of

the following:

Better motor-unit recruitment

Enhanced motor-unit synchronisation

Greater central input to the motor neuron

Decrease in presynaptic inhibition.

The same authors also propose that PAP may be produced by local muscle

changes such as phosphorylation of the myosin light chain. This process is

explained by heavy exercise increasing the amount of Ca2+ in the sarcoplasmic

reticulum, and the sensitivity of the myofilaments to Ca2+. Essentially more Ca2+

at a cellular level enables more ATP to be produced, which in turn enhances

power production. The authors of this study do not comment on whether they

believe these local mechanisms are trainable or simply transient alterations.

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Ebben and Watts (10) completed a review of complex training in 1998 and

offered several explanations for PAP, listing the following possible factors

Neuromuscular

Hormonal

Metabolic

Myogenic

Psychomotor.

However only neuromuscular mechanisms are discussed in any detail, which

may mean that the other factors were either not well understood at the time

and/or were not supported in the literature. These authors also mention that the

fatigue associated with heavy weight training may increase motor-unit

recruitment during subsequent plyometric exercise. At this point it is important to

note that more recent literature (6) tends to emphasise neural stimulation rather

than fatigue when referring to PAP.

Ebben and Watts (10) also cite a study by Fees in 1997 that attributes PAP to the

reciprocal inhibition around a joint caused by agonist stimulation. That is, a heavy

bench press minimises any restrictive contraction of the rhomboids (antagonist)

for the subsequent plyometric exercise. However it is known that this inhibition

occurs within the first month of training for inexperienced lifters anyway. Whether

this effect can be maximised in experienced trainers through CT has not yet been

determined.

McBride et al. (18) and Gourgoulis et al. (12) also support the neural activation

theories proposed by Docherty et al. (6). The former expand by proposing that

CT training may increase neurotransmitter release in afferent nerves. They also

reviewed several articles indicating that fast-twitch (FT) dominant muscles

produce greater potentiation.

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Dan Baker has published prolifically on the topic of CT and he mentions some

alternate mechanisms to explain PAP. His 2003 paper (1) mentioned the series

elastic component of the musculo-tendinous unit as a possible contributor. He

commented that a resistance of 65% of 1repetition maximum (1RM) would

favourably increase stiffness but heavier resistances (85-90% 1RM) would not be

optimal. However one would wonder if 65% of 1RM would be sufficient to

achieve enough neural stimulation that is the main producer of PAP as outlined

in articles reviewed thus far (6,10,18,12). Training age and experience with CT

would no doubt be factors that would influence the optimal intensity to achieve

optimal PAP.

Baker (1) also suggests that the golgi-tendon organ (GTO) and Renshaw cell

activation may be reduced as a result of a heavy stimulus applied to a muscle.

Inhibition of these structures would prove advantageous considering their role in

monitoring and limiting maximal motor-unit activation as a protective mechanism.

However as has been mentioned, the reduction of feedback from these inhibitory

structures can be seen in the first month of training in novices. Whether this

inhibition is enhanced to a greater degree through CT has yet to be confirmed.

To summarise, the primary mechanisms for PAP appear to occur at a neural

level and relate to a reduction of inhibition and enhanced motor unit excitability.

Most authors acknowledge that local muscle factors may contribute to PAP but

the literature is not extensive in comparison to neural factors.

Upper body and lower body studies

Quite a number of studies have been done investigating the effect of the squat

exercise on subsequent vertical jump performance (7,11,12,14,15,17-19,21,22).

Obviously the investigation of this “pair” of exercises is to do with their

biomechanical similarity, a prerequisite that was outlined by Verhoshansky in

1973 (11).

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Several studies reviewed concluded that CT enhanced subsequent expression of

lower-body power (7,12,17,21,22). Duthie at al. (7) used 11 women to compare

complex and contrast training methods through squats and jump squats. They

found that contrast training did increase power output (although this was non-

significant) but only for those with high strength levels. Gourgoulis et al. (12)

published similar findings through their investigation of vertical jump ability.

Subjects with greater maximal strength improved vertical jump by 4.01% after

performing 5 x 2 half squats from 20-80% of 1RM. Those with lower strength

levels only improved by 0.42%. However the authors in this study didn’t specify

the training age of participants, merely stating that they were “physically active.”

McBride et al. (17) conducted an 8-week training program on 26 subjects who

performed jump squat training at either 30% or 80% of 1RM. They found that the

30% group improved peak power and peak velocity at all intensities (30, 55 and

80% of 1RM). This group also improved 1RM and 20m-sprint time indicating a

transfer to a sport-specific activity. Interestingly the group that trained at 80% of

1RM improved peak power and peak velocity at higher intensities (55 and 80% of

1RM) and increased 1RM, however 20m sprint times were significantly slower.

This then suggests that to transfer gym-based power to a sport specific activity

(such as a 20m sprint) lighter resistances should be used. However it should be

pointed out that this study did not employ CT or contrast training, making

comparison with other studies cited in this review difficult.

Similarly Tricoli et al. (21) investigated the effect of olympic style weightlifting

exercises compared to plyometric training. They found that the olympic lifts were

more effective at improving squat jump, 10m sprint and vertical jump. The

subjects in this study were all physical education students who underwent 3

months of lower body specific training prior to the study and all were experienced

weight trainers.

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Although neither of these studies (17 and 21) used CT, their results indicate that

a stimulus greater than plyometrics but less than 80% of 1RM is required to

achieve a positive transfer to field-based activities such as sprinting.

Smilios et al. (22) found a short-term increase in countermovement jump

occurred when intensities of 30% and 60% of 1RM was applied in the form of

either a heavy squat or jump squat. Their subjects all had a training age of 2-3

years and participated in sports requiring explosiveness such as basketball,

volleyball and soccer. The fact that the improvements were quite similar for vastly

differing stimuli (heavy squat v’s jump squat and 30% v’s 60% of 1RM) suggests

that for experienced trainers, a wide range of variables will provide a subsequent

enhancement of power. Other investigators (7,12) also discovered that the most

significant power gains occurred in those with higher strength levels.

Upper-body CT has not received as much attention as lower-body but some

interesting findings exist nonetheless. In 2003 Baker (1) found that a set of bench

press performed at 65% of 1RM improved bench press throw by 4.5%. In 2005

Baker and Newton (4) investigated the effect of an agonist-antagonist complex

series. That is, subjects were tested on bench press throws but the experimental

group performed bench pulls (antagonist) between tests. The experimental group

improved by 4.7% in post-testing. In both of Baker’s studies (1,4) subjects were

professional rugby league players who were experienced in strength and power

training methods.

However not all studies have found a positive effect with upper-body CT.

Hrysomallis et al. (13) found that 5 reps of 5RM bench press did not improve

power produced from an explosive push up on a force platform. Subjects had an

average training age of 3.1 years. Ebben et al. (9) used EMG and kinetic analysis

to conclude that a set of 3-5RM bench press did not increase ground reaction

force or EMG when performing subsequent medicine ball throws. This study

used basketball players experienced in weights and plyometric training.

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Brandenburg (5) found that a set of bench press at varying intensities (100%,

75% or 50% of 5RM) did not have a positive effect on bench press throws. This

study only used 8 subjects, some of which had limited exposure to power training

(no subjects had performed bench press throws previously). The author also only

used average power as a measure over 3 throws (not peak power), and indicates

that this may have influenced the results.

It should be noted that all of these studies used high intensity interventions

(5RM) with subjects not experienced with strength/power training (with the

exception of Ebben et al.). Therefore one must consider that fatigue may have

still been evident when the post-testing was conducted. The variable of recovery

will be discussed in greater detail in the next section.

Analysis of both upper and lower body CT studies reveal that lower-body CT

appears to be more effective at improving power expression, although more

research has been done in this area. It also appears that subjects need to

posses a sound strength base and training age to demonstrate an increase in

power production.

Suggested training variables

Throughout the work done on CT, the manipulation of training variables appears

to have a significant impact on the magnitude of PAP and resultant increase in

power production. Of particular importance appear to be the variables of training

intensity and recovery.

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Exercise mode is not a very controversial discussion point, as most authors

have advocated the use of biomechanically similar activities for CT. The most

common examples being bench press-bench throw and squat-squat jump. The

theory being that PAP is more pronounced if the heavy exercise stimulates the

same (or similar) neural pathways to the power exercise. However Baker (4)

experimented with the use of a heavy antagonistic exercise (bench pulls) and

found a significant increase in bench throw power (4.7%).

This then suggests that the contrasting activities do not need to be as

biomechanically similar as has been previously suggested. Of course more work

of this nature needs to be done even though the same author found that a

“typical” contrast using bench press – bench throws yielded a similar power

increase of 4.5%. Perhaps with trained individuals, the variables of intensity and

recovery are more important than the mode of exercise?

Intensity of the “heavy” exercise is more varied in the literature ranging from

30% of 1RM (22) to 90% of 1RM (18). The use of 5RM is common

(5,14,13,15,19), however a landmark study by Gullich and Schmidtbleicher [cited

in Docherty et al. (6)] found that 3-5 maximum voluntary isometric contractions

(MVIC) was “sufficient to increase explosive force in the upper and lower

extremities and could be used to enhance performance and training” (p 53).

However there has not been much subsequent support in the literature for the

use of MVIC’s.

As was mentioned previously, those athletes with higher initial strength levels

appear to gain more benefit from CT. Perhaps initial strength levels relate to the

ideal intensity that can be applied to gain maximal PAP? Baker has conducted

his work with elite level Rugby League players and has advocated the use of

intensities around 50-65% of 1RM. Smilios (22) found that for lower-level

(regional) athletes, at least 60% of 1RM should be applied for PAP.

10

Those studies involving athletes that did not find a positive response from CT

used higher intensities of 3-5RM (7,9,14). This then suggests that lighter

intensities may produce a more positive response in athletic populations.

Recovery is another variable that has a significant impact on the success of CT.

PAP does operate in a certain “window” so if a further stimulus is applied too

soon, fatigue will be evident. However too much recovery will result in the

individual missing the window of opportunity, as the potentiation effect will have

subsided. Certainly more long-term studies are necessary to determine if trained

individuals can sustain this PAP effect for longer.

When comparing the literature, a wide range of rest intervals have been trialled

from 10 seconds up to 5 minutes. With his elite power-trained athletes, Baker

(1,4) found that 3 minutes rest between strength and power exercises revealed

that potentiation was still present. Smilios (22) also found a positive effect with 3

minutes recovery between strength sets (only 1 minute rest between contrast

sets). Several other authors applied 3 minute rest intervals (13, 15) but found no

positive effect using a CT protocol. However both of these studies were

conducted on non-elite subjects with small sample sizes (12 and 8 respectively).

In fact Jones and Lees (15) admit that greater power output was demonstrated

by their experimental group, even though the difference was not significant.

A number of studies have used 5-minute rest intervals (7,9,12,19) with varying

results. Duthie et al. (7) and Gourgoulis et al. (12) found that those with higher

strength levels showed greater PAP. However Scott and Docherty (19) and

Ebben at al. (9) did not show any evidence of PAP with 5 minutes recovery. It

should be noted that the former study (19) did not use athletes as subjects.

Brandenburg (5) used 4-minute recovery intervals and found no evidence of

PAP, however his subjects were only recreationally trained and did not allow use

of the stretch shortening cycle during testing.

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Jensen and Ebben (14) investigated a number of recovery intervals from 10

seconds to 4 minutes. They found no positive response to CT but do speculate

as to whether results would have been different with a recovery period greater

than 4 minutes. It was noted that a 10 second recovery period had a negative

effect on subsequent power output.

There is no doubt that the degree of potentiation is related to individual factors

such as strength levels and training history with CT protocols. Therefore a trial

and error approach may be required to determine the optimal rest interval for

different athletes across different sports. Looking at the literature, 3-5 minutes of

recovery does appear reasonable for most athletic populations.

Volume of the intervention is another important variable that may influence the

degree of PAP. Those studies that examined higher-volume (more than 1 set)

strength exercises all demonstrated improved power output (7,12,22). However 2

of these studies (7,12) commented that a more pronounced effect occurred with

stronger athletes. Fleck and Konter (11) also commented that Verhoshansky

utilised 2 sets of a strength exercise to get a positive response, and it may be

assumed that he was working with elite athletes who possessed greater strength

levels.

Many studies (1,4,5,9,13,14,15,18,19) have examined a lower-volume (1 set) of

strength exercises, and reported mixed results. A number of studies did not find

any improvement in subsequent power production after 1 set of a heavy strength

exercise (5,9,13,14,15,19), which may suggest that athletes may need more than

1 set to achieve the neural stimulation associated with PAP. However 3 studies

(1,4,18) found that 1 set was sufficient to achieve a positive response, and all of

these examined gridiron or rugby league athletes.

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Therefore the jury still appears to be out as to whether a single-set or multiple

sets are necessary to achieve PAP. Due to the inverse relationship that exists

between volume and intensity, one may assume that CT protocols using a single-

set of strength exercises would do so at a greater percentage of 1RM.

Periodisation of CT

If the coach has decided to implement CT for the physical preparation of his/her

athletes, the next decision is when to use this form of training. Most of the studies

that did not find a positive result with CT (5,9,14,15), commented that this form of

training had no adverse effect on subsequent power output and could be used as

a means of maximising available training time. Therefore it appears that, at

worst, CT could effectively be used during phases of the season where training

efficiency is important, such as the competitive phase.

Ebben et al. (8) and Simenz et al. (20) conducted surveys of major league

baseball and national basketball association strength and conditioning coaches.

Understandably coaches were not willing to discuss the specifics of their training

programs, but many did indicate that they used CT (7/21 coaches for baseball

and 12/20 for basketball). Similarly, 8/21 baseball and 9/20 basketball coaches,

reported that they used plyometric training year-round. From these statistics we

cannot say that all of these coaches used CT throughout the year, but they do

indicate that CT is implemented at different stages of the training year.

Traditional methods of periodisation suggest that power training should be

emphasised when attaining a peak, which typically occur at the start of the

competitive season and for finals. Therefore CT is most likely to be utilised during

the specific-preparation phase and as part of the lead-up to end of season

games in team sports. However individual sports that do not compete on such a

consistent basis may incorporate CT more regularly as a part of their build-up for

major events.

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Conclusion

The evolution of training methods in recent times has resulted in increasing

scientific investigation into methods such as CT. Proponents of this training

method have stated that the main physiological response is an increase in PAP

which enables increased power production for the plyometric activity. Although

studies conducted thus far have not reached a consensus, it does appear that

CT can play an important role in athletic training for increasing power production

and/or maximising training efficiency.

More studies are required to determine the optimal variables for CT but in the

meantime, coaches are encouraged to experiment with the key training variables

of volume, intensity and recovery to develop a model that is suited to their sport

and athletes. Strong consideration must also be given to the initial strength levels

of the athlete/s and experience with power training methods. These two factors

appear to be prerequisites for significant increases in power production.

Suprisingly there has been minimal investigation on the effect of CT using

biomechanically unrelated exercises. It would be interesting to see if lower body

strength exercises would result in PAP in the upper body and vice versa. Baker

has already demonstrated that the use of an antagonist strength exercise can

augment power production (4) for the bench press throw. Such work should

provide a strong basis for scientists wishing to further investigate this

phenomenon.

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