Science of Sport: The potentiation effect - can one training mode really enhance another?

How To Win: Free regular world-class triathlon training tips. Enter email here:

Designing a periodised training programme to enhance speed and power can be mentally taxing – so much so that those on the hunt for these prized attributes may even develop a ‘complex’! Complex training describes a power-developing workout that combines weights and plyometric exercises. About 10 years ago, these workouts were greeted with great acclaim as research indicated that they could significantly enhance fast-twitch muscle fibre power and, therefore, dynamic sports performance. However, more recent research has highlighted a number of questions about complex training as well as some new potential benefits.

The key physiological vindication for these workouts is the ‘potentiation’ effect – ie the enhancing effect one training mode can have on another. Initially, research focused on the potentiation of the plyometric exercises by the weights exercises (note that the exercises involved are ‘paired’ and work the same muscle groups). More recently, though, researchers have turned their attention to whether weightlifting power could be enhanced by the prior performance of a plyometric exercise.

Fast-twitch muscle fibre holds the key to increased dynamic sports performance, since these fibres can contract 2-3 times faster than their slowtwitch counterparts. Type IIb fast-twitch fibres are the turbochargers of the power athlete’s engine (as opposed to type IIa ‘transitional’ fast-twitch fibres, which can be modified for either power or endurance purposes). But these turbochargers are notoriously difficult to activate fully, since there can be as many as 1,000 of these fibres to every one motorneuron in their muscle motor unit.

A motorneuron acts as a sort of ignition key to its bundle of power-producing fibres. Under normal training and competition situations, ‘turning the key’ requires a highly focused mental approach. Simply going through the motions will not excite type IIb fibres enough to achieve a PB weight lift or series of bounds.

In fact, it is argued that even when an athlete is ‘psyched’ – ie applying great mental pressure to unleash the might of their fast-twitch fibres, this may still not be enough.

It is because of this that power combination workouts, with their seeming ability to fully potentiate fast-twitch fibre as if by magic, have become very appealing.

The way plyometric and weights exercises are ordered into a power combination workout can have a significant effect on training adaptation and potentiation. There are two basic approaches:

• Complex training. This involves performing sets of weight training exercises before sets of related plyometric exercises – eg three sets of 10 half squats, before three sets of 10 jump squats. Such combinations of sets are known as ‘complexes’;
• Contrast training. This involves alternating sets of first weights then plyometric exercises – eg one set of 10 half squats followed by one set of 10 jump squats, repeated over three sets.

Complex training effects

It is argued that the weights exercises for both complex and contrast training workouts should be in excess of 70% of 1 repetition maximum (1RM), since lighter loads are considered inadequate for activating type IIb fibres and setting off the potentiation effect.

Although a great deal of research points to the success of power combination workouts (see PP 114 Feb 99 and PP 125 Nov 99), a number of questions have been raised – not least over the potentiation effect itself. Jones and associates, for example, looked at complex training and the effect heavy squats had on counter-movement jump (CMJ) and depth jump (DJ) height, and on muscle activity, as measured by electromyography (EMG), in the subsequent plyometric exercise ⁽¹⁾.

Eight strength-trained men were involved in the research under two conditions:

1. Complex training, performing five squats at 85% of 1RM, followed by the first set of jumps, with the second, third and fourth sets performed three, 10, and 20 minutes after squatting;
2. Control condition, involving only CMJ and DJ performance.

The team found no positive potentiation for any CMJ performance variable or EMG activity, regardless of muscle or phase of jump; nor were there any significant effects of the squats on DJ performance. However, EMG activity in the biceps femoris (hamstrings) during the propulsive phase of the DJ was found to be significantly higher after squatting (although this did not improve jump performance). The researchers concluded that complex training did not enhance plyometric muscular activity.

There are a number of potential explanations for these findings. First, it is possible that greater exposure to the complex training workout could have produced greater improvements in plyometric performance: the fact that higher EMG activity was discovered in the hamstring muscles during depth jumping indicates that more fast-twitch fibres were being recruited, which in time could have provided more propulsive power.

Order of exercises

Secondly, the order of the exercises could have affected the outcome, and the results might have been different if a contrast methodology had been used. (Research has suggested that the contrast method may be more effective at eliciting potentiation in those with little experience of power combination training or lower strength levels, of which more later.)

Research by Duthie and associates examined jump squat power in complex, contrast and ‘traditional’ training workouts⁽²⁾. Eleven women with varying strength levels completed three randomly ordered testing sessions, as follows:

1. Traditional – completing sets of jump squats before sets of half squats;
2. Complex – sets of half squats before jump squats;
3. Contrast – alternating sets of half squats and jump squats.

The researchers found no significant enhancement of jump squat performance with any method in the subjects with lower strength levels. However, the stronger women demonstrated superior jump squat performances with contrast training, and the researchers concluded that this method was more effective for increasing power output in athletes with relatively high prior strength levels.

Other research, such as that by Gourgoulis et al, has also pointed to the importance of prior strength levels on power combination workout outcomes⁽³⁾. They found that pre-squatting significantly enhanced the vertical jumping ability of stronger participants by 4.01%, but of weaker ones by just 0.45%.

In practical terms, this means that coaches must be mindful of individual strength levels, and be prepared to vary the ordering of power combination workout training elements accordingly in order to achieve the most significant adaptations. They should also be prepared to vary the loading of the weights exercises (between 70 and 90% of 1RM) and the number of repetitions. Recording the results will highlight which workouts produce the best results and the physical attributes performers may need to work on to produce the best potentiation gains.

Training maturity should also be taken into account as an important potential variable in the success of power combination workouts – particularly when it comes to the order of exercises. Research by the Soviet sports scientist Yuri Verkhoshansky (the so-called ‘father’ of plyometric training) showed that novice track and field athletes developed less explosive strength when they performed heavy weights exercises before their plyometrics (rather than vice versa) over a 12-week training period. This may simply be because the heavy squatting tired the athletes’ relatively untrained muscles to an extent that impaired subsequent explosive performance.

The length of rest periods between exercises is a further matter for debate in connection with power combination workouts. A complex training workout in its ‘purest’ form is designed to create an almost immediate potentiation effect. The rest between exercises and sets is normally kept to about two minutes – long enough to minimise fatigue but short enough to create and maintain potentiation, therefore optimising power output throughout the workout. (Note, though, that some power combination workouts are designed to deliberately develop power endurance and use shorter recoveries and greater numbers of exercises. These workouts, applicable to such sports as basketball and rugby, inevitably generate greater fatigue that can inhibit potentiation.)

Research by Fastouros considered the rest factor and the value of combined training methods in a study of 41 healthy men divided into three training groups, as follows⁽⁴⁾:

1. Weight training exercises only;
2. Plyometrics only;
3. Plyometrics and weights exercises on the same day but, crucially, not during the same workout. This group performed the weights exercises first, followed by plyometrics some three hours later.

The team found that, although all training methods improved vertical jump and squat performance, the athletes combining plyometrics with weights experienced the greatest performance enhancement – a maximum squat improvement of 36kg, compared with 16.4kg for the weight training group and 28kg for the plyometric group.

This research has positive implications for those embarking on power combination training. Separating the two training elements on the same training day with a longer recovery time could avoid fatigue yet still maintain potentiation.

Most power combination training research has focused on the potentiation of plyometric exercises by weights work. However, research by Masamoto looked at the effects of plyometrics on weight training, particularly on 1RM squat performance⁽⁵⁾. Twelve trained men participated in three 1RM testing sessions, separated by at least six days of rest. In the first session, they performed a series of weights sets with increasing loads until 1RM was determined; in the second and third sessions, they performed either three double-leg tuck jumps or two depth jumps 30 seconds before each of three 1RM attempts, interspersed by at least four minutes’ recovery.

The researchers discovered that performing a plyometric exercises before going for a 1RM best had a positive effect. Tuck jumps upped the average squat performance to 140.5kg, and depth jumping boosted it to 144.5kg, compared with 139.6kg with no prior plyometrics. This is obviously very encouraging news for power and weight lifters and anyone else looking to increase general muscular strength via weight training.

Can power combination workouts enhance competitive as well as training performance? Research by Matthews looked at the effect of pre-squatting on 20m sprint performance⁽⁶⁾. During the control condition, participants performed two 20m sprints separated by 10 minutes’ rest. During the experimental condition, the second sprint was preceded by five squat repetitions with a load equal to each participant’s five repetition maximum (5RM). While the researchers found no improvement between the first and second sprints in the control condition, there was a mean improvement of 0.098 seconds when the second sprint was preceded by the squats.

Squats and sprint cycling

Similar findings were made by Smith et al, who looked at the effect of squats on a very intense 10- second bout of sprint cycling⁽⁷⁾. In this study, involving nine men, the time between squatting and sprint performance was varied over three conditions, as follows:

1. Control – a 1RM squat attempt immediately before the 10-second cycle sprint;
2. 10 squats at 90% of 1RM five minutes before the sprint;
3. As for 2 but with a 20-minute rest before the sprint.

The researchers noted significant increases in average power and average power relative to body weight with the second condition and concluded that this protocol could be useful in enhancing sprint performance.

The implications of this research are obviously immense, although in practice it may be difficult to schedule in five minutes of squatting before a 100m sprint final! However, you may be able to get away with performing the following potentiating exercises to be completed five minutes before competition – as long as you experiment with them in training first:

• Sprinting/jumping/throwing – perform three single leg-squats on each leg;
• Sprinting/jumping/throwing – perform five squats with a willing training partner/team-mate on your back;
• Weightlifting – perform five throw-and-catch medicine ball chest passes against a wall as fast as possible and/or complete three tuck or depth jumps.

Power combination training, despite some of the reservations expressed earlier, seems to offer a great deal for those in search of increased fasttwitch muscle power. However, coaches need to take careful account of prior strength levels, training maturity and the types of power combination workouts most appropriate for their athletes, in order to get the most from them.

John Shepherd

References

1. J Strength Cond Res. 2003 Nov; 17(4):694-700
2. J Strength Cond Res. 2002 Nov; 16(4):530-538
3. J Strength Cond Res. 2003 May; 17(2):342-344
4. J Strength Cond Res. 2001 Nov; 14(4):470-476
5. J Strength Cond Res. 2003 Feb; 17(1):68-71
6. Res Sports and Medicine 2004 April/June; vol12, no2
7. J Strength Cond Res. 2001 Aug; 15(3):344-348

How To Win: free regular running training tips. Enter email here: