The aim of the pole vault event is for the athlete to jump over as high a bar as possible, using a pole for assistance (Frère, L’Hermette, Slawinski, & Tourny-Chollet, 2010). The take-off has been described as the most important phase of the pole vault (Bassement, Garnier, Goss-Sampson, Watelain, & Lepoutre, 2010; Plessa, Rousanoglou, & Boudolos, 2010) as it is the transition between the horizontal running and aerial phases and is also where the athlete’s kinetic energy begins to be transferred into potential energy in the pole (Frère et al., 2010), these transitions being key to a successful vault. For the purposes of this essay the term ‘take-off’ will follow what Frère (2009) defines as the ‘impulse phase’, that is from the moment of the final foot contact with the ground until it leaves the ground again, during which time the vaulter imparts a force to create the re-orientation of trajectory also known as a jump.
Olympic weightlifting activities are often used as part of an athlete’s physical preparation in order to increase their power, speed and strength which have an impact on their jumping ability (Waller, Townsend, & Gattone, 2007). The similarities between the athletic qualities trained when performing the snatch exercise and the vertical impulse needed for a successful pole vault take-off (Angulo-Kinzler et al., 1994; Hay, 1993), plus the need for a vaulter to be very strong in the shoulders, arms and trunk (Angulo-Kinzler et al., 1994) would suggest that the snatch weightlifting exercise may be a beneficial exercise for a pole vaulter to perform as part of his/her gym training program. Therefore this essay will explore the specificity of using the snatch to improve a pole vaulter’s take-off, using the framework of dynamic correspondence as set out by Verkhoshansky and Siff (2009) in order to perform the comparison. This framework consists of five criteria under which a training exercise should match or exceed the activity being trained for, in order to appropriately train the required motor system qualities and achieve an improvement in performance.
Whilst the arms and shoulders play a massive role in transferring a vaulter’s kinetic energy into the pole (Cassirame, Sanchez, Vanhaesebrouck, Homo, & Frère, 2017; Frère, 2009; Frère, Göpfert, Slawinski, & Tourny-chollet, 2012; Frère et al., 2010) this essay will concentrate on the forces generated by the lower limbs during the two skills as the International Association of Athletics Federations define the pole vault as a jump event (“Disciplines,” n.d.) and the lower limbs play the greatest role in generating the vertical forces to initiate this jump (Frère, 2009).
The first of the dynamic correspondence criteria is the amplitude and direction of movement during the exercises (Verkhoshansky & Siff, 2009). The snatch exercise involves lifting a barbell from the ground to arm’s length above the athlete’s head in one movement. (Hadi, Akkus, & Harbili, 2012; Waller et al., 2007). The athlete begins by squatting down to take hold of the bar, before using a powerful triple extension on the ankles, knees and hips to lift the bar (the pull), he then performs a full squat to get under the bar and catch it above his head (the catch), before standing again to complete the lift (the recovery). Figure 1 demonstrates the lifting technique, as far as the catch position, as described by Mantek and Vater (2013).
Figure 1. Snatch technique as far as the catch position. Manteck and Vater (2013)
The pole vaulter also uses a forceful triple extension of the ankle, knee and hip to create an upwards motion, however this is only with one leg (the take-off leg), the other (free) leg being flexed at the knee and hip and the ankle dorsiflexed to create the take-off position shown in figure 2 (Hay, 1993).
Figure 2. The pole vault take-off position, showing the forces being applied by the hands on the pole. Hay (1993).
The pole vaulter runs into the take-off and so whilst there is a slight reduction in the hip height above the ground during the penultimate step (Bogdanis & Yeadon, 1994) the degree of leg flexion when starting the take-off step is not as great as that of the start position of the snatch. This difference is clearly demonstrated by comparing the knee angles in the starting positions, with Figure 1 showing a starting angle of 65˚ for the snatch compared to the 145±13.3˚ reported by Bassement et al. (2010) for expert vaulters (although they were looking at athletes performing a take-off exercise from a short run-up rather than the whole vault, which they concede may mean that the reported figures might not accurately reflect what happens in a vault from a full run-up, the figure does fit the range of between 130˚ and 150˚ reported by Linthorne and Weetman (2012) when altering the run-up velocity of a vaulter).
Whilst an athlete performing a snatch will follow a pattern of pull, catch, recovery as described above, there is also some knee flexion after the bar has passed the knees during the pull, in order for the athlete to re-orientate himself into a more advantageous position for the explosive triple extension of the ankle, hips and knees which follows (Liu et al., 2018). This knee flexion (termed the transition) allows the pull phase to be split in two for analysis, termed the first and second pulls (Garhammer, 1993). The pole vaulter’s take-off leg will also flex slightly at the knee and ankle during the gait cycle but it can be argued that this should be minimised as a greater joint stiffnesses will help with an efficient energy transfer between the horizontal velocity of the run-up and vertical velocity of the vault (Bassement et al., 2010; Cassirame et al., 2017).
It should also be noted that whilst the pole vaulter directs his effort upwards (Angulo-Kinzler et al., 1994; Hay, 1993), and Morlier and Mesnard (2007) describe the vertical force that can be applied to the pole as a key performance criteria, the horizontal velocity created during the run-up results in an actual take-off angle of between 16˚-20˚ (Bogdanis & Yeadon, 1994; Frère et al., 2010; Plessa et al., 2010), indeed if the athlete were to actually take off vertically then the pendulum effect required to bend the pole would be impossible (Plessa et al., 2010).
Given these kinematic differences it can be argued that the correspondence between the two skills is relatively weak for this criterion, though there are greater similarities when only certain parts of the snatch (the transition and second pull) are considered.
The second dynamic correspondence criterion is the accentuated region of force production. Plessa et al. (2010) reported peak vertical ground reaction forces early in the pole vaulter’s take-off stride, with the passive peak occurring 15±5ms after foot contact and the active peak occurring 36±13ms after contact. Bassement et al. (2010) also found high levels of EMG activity in the vastus lateralis and biceps femoris muscles around touchdown of the take-off leg, a co-contraction which was theorised to support/stiffen the leg for efficient energy transfer.
The peak horizontal propulsive force occurred later in the take-off stride, 108±11ms after touchdown, which places it during the triple extension of the take-off leg (Plessa et al., 2010). Figure 3 combines the data of Bassement et al. (2010)and Plessa et al. (2010) to show the ankle, hip and knee angles during the take-off stride and where the peak ground reaction forces occur.
Figure 3. Combined data from Bassement et al. (2010) and Plessa et al. (2010) showing the angles of the ankle, hip and knee between touch down (TD) and take-off (TO) of the take-off stride and where the peak ground reaction forces occur. Fz represents the vertical ground reaction forces, Fythe horizontal ground reaction forces.
In the snatch there is a consensus that peak force and power are generated during the second pull (Garhammer, 1993; Hadi et al., 2012; Harbili, 2012; Ho, Lorenzen, Wilson, Saunders, & Williams, 2014; Kipp & Harris, 2014; Liu et al., 2018). Whilst peak movement velocity will be discussed in the third criterion it is useful to note that the bar velocity increases during the second pull by 0.5-0.8m.s-1 (Harbili, 2012). As F=ma and the bar has a fixed mass (m), then this increase in bar velocity must be created by a large application of force happening during the second pull. Liu et al. (2018) studying elite lifters reported the peak vertical velocity of the bar as occurring at a knee angle of 154.8±8.9˚ and a hip angle of 147.1±8.2˚, whilst Ho et al. (2014) report that peak bar velocity occurs at the end of the second pull, (Harbili (2012)reports angles at the knees of 169.7±3.5˚ and at the hips of 191±5.9˚ for this position). These ranges of values would suggest that a high degree of similarity exists between the joint ranges in which maximal force is produced during the two skills.
The third of the dynamic correspondence criteria is the dynamics of effort. Verkhoshansky and Siff (2009) state that the effort exerted in training should match or exceed that required in the sports movement, quantifying this by looking at variables such as the force generated and velocity of movement.
Bogdanis and Yeadon (1994) reported a vertical take-off velocity for elite vaulers of around 2m.s-1. This is only slightly faster than the snatch as the peak bar velocity is reported by Ho et al. (2014) to be between 1.68±0.03m.s-1 and 1.98±0.09m.s-1, again looking at elite level athletes.
The vertical forces generated during a pole vault take-off can be influenced by the athlete’s gender and the technique used. As discussed during the second criterion Plessa et al. (2010) split the vertical ground reaction forces into passive and active peaks, that represent the initial impact and then the active vertical force generation. The passive peak of 10.2±1.9 times body weight (BW) reported by Plessa et al. (2010) for the female vaulters they were studying is corroborated by the 10 BW figure reported by Brüggemann, Arampatzis, Komi, & Schade (2002) as the impact force for those vaulters who planted the pole early in the take-off, which tended to be (though not exclusively) female. Male vaulters have a higher approach velocity than females (Brüggemann et al., 2002), plant later and have higher kinetic energy levels at take-off (Schade, Arampatzis, Brüggemann, & Komi, 2004; Warburton, 2015). Christensen, Francis, Keller, Bradford, & Hatterman-Valenti (2014) examined the positioning of the take-off foot in relation to the upper hand on the pole (a sign of the plant technique being used) and found that when compared to an early pole plant, a late plant allowed the horizontal breaking forces to be reduced (-1.09 BW to -0.88 BW) and propulsive forces to be increased (0.12 to 0.16 BW). Unfortunately, despite using a mixed group of vaulters, they did not report results separated by gender which would have allowed matching of the findings to the trend seen by Brüggemann et al. (2002) and Schade et al. (2004) for the different genders to use different techniques. The results do however support the suggestion that using a late plant allows higher kinetic energy levels to be carried into the aerial phase. In contrast to this effort to maximise horizontal forces Hadi et al. (2012) argue that despite some horizontal displacement of the bar during a snatch an efficient lift minimises horizontal forces. There is a lack of research in the kinetics of the snatch catch phase but Comfort, Williams, Suchomel, and Lake (2017) looking at the clean exercise reported that the vertical forces generated by the athlete descending into the catch position were absorbed through a long impulse (950ms) with a mean force of only 2.2 BW, whilst Lauder and Lake (2008) looking at the power snatch reported mean values of 1.39 BW, both considerably lower than the forces reported for the pole vault.
Findings for the pole vault’s active vertical peak force are much more favourable for comparison to the snatch than the variables discussed above. Plessa et al. (2010) reported a peak of 4.6±0.6 BW, whilst Christensen et al. (2014) gave values of between 3.6 BW and 3.9 BW depending on plant timing. Garhammer and Gregor (1992) gave values of between 3.6 BW and 4.2 BW for the snatch lift, whilst Jensen and Ebben (2002) reported values between 3.9 BW and 4.8 BW for athletes performing a hang snatch (a snatch performed with the bar starting at the knees rather than the ground, corresponding to the positions of the second pull). Therefore, despite the fact that the snatch can not match the horizontal forces or the vertical impact forces of the pole vault, the similar vertical velocities and vertical forces reported in the active phases of the take-off suggest that the snatch can provide a suitable training stimulus to meet the requirements of this criterion.
The next of the dynamic correspondence criteria is the rate and time of force production. The pole vault take-off, at around 130ms (Plessa et al., 2010; Warburton, 2015), occurs faster than the 940ms to the catch position of the snatch (Hadi et al., 2012), though the duration of the second pull is more directly comparable at 120ms. Therefore looking at the second pull (or at a hang snatch performed within this range of motion) may allow a better comparison to the vault take-off, and indeed the mean rate of force development figure reported by Plessa et al. (2010) of 38023N.s-1 for the take-off fits the hang snatch results of Jensen and Ebben (2002) at between 80% and 90% one repetition maximum (1RM) (378161±73370N.s-1 and 401471±84621N.s-1 respectively). It should again be noted though, that the pole vault figures relate to female athletes, whilst the athletes were performing the hang snatch were male. These gender differences may alter the percentage of 1RM at which the greatest correspondence is found, but given the similarities it should be safe to assume that for at least part of snatch (the second pull) this criterion shows a correspondence between the two skills. Manipulating the percentage of 1RM to maximise correspondence will be further discussed later as part of the practical implications.
The final criterion is the regime of muscular work, which is defined as the characteristics of the muscular work being performed (Verkhoshansky & Siff, 2009). In both exercises similar energy systems are used as the athlete performs a single maximal effort then has a period of rest before the next repetition. For the pole vault the minimum time between two jumps can vary between level of competition and how many athletes are still in the competition, but it is generally not less than two minutes (“Pole Vault,” n.d.). In a weightlifting competition the athlete will be allowed a minimum of 2 minutes if he is required to perform consecutive lifts (“Technical and competition rules & regulations,” 2019).
One point of contrast is that the limb actions are asymmetrical in the pole vault, compared to the symmetrical action during a snatch, as described in the first criterion. The concentric strength based muscle action during the first pull of the snatch also bears little resemblance to the pole vault take-off, but where similarities do exist is in the spring like actions of the legs following the transition and into the second pull. Hadi et al. (2012) argue that the knee flexion seen in the transition phase before the second pull acts to store elastic energy in the knee extensor muscles, which is then utilised during the second pull to create the peak force, power and velocity described above. A similar stretch-shortening cycle has also been described as using elastic energy to efficiently transfer energy between the breaking and propulsive phases of the take-off leg for the pole vault and long jump (Plessa et al., 2010; Seyfarth, Friedrichs, Wank, & Blickhan, 1999). Whilst the second pull of the snatch has a better dynamic correspondence than the full snatch to the pole vault take-off, for the reasons described above, to only perform a hang snatch from the knee during a vaulter’s strength training may limit the involvement of this stretch-shortening cycle. One alternative way to utilise this in a vaulter’s training would be to use plyometric exercises, indeed given the similarities in the elastic use of energy and the asymmetrical limb actions, it could be argued that plyometric exercises such as bounding or hopping have a greater dynamic correspondence to the pole vault take-off than the snatch does. For example bounding can produce significant forces in both the initial foot impact and subsequently in both horizontal and vertical directions (Kossow & Ebben, 2018) which better replicate the demands on the take-off leg as described by Seyfarth et al. (1999), than the almost purely vertical forces of the snatch (Hadi et al., 2012). Kossow and Ebben (2018) state that athletes who need to develop horizontal power should perform horizontal plyometric exercises and given the take-off angle of less than 20˚ it could be argued that the pole vault fits into this category. A repeated bounding action could also be of benefit to the run-up which precedes the take-off.
Whilst plyometric training has been shown to develop maximum strength and rate of force development in athletes, there still is a role for weightlifting exercises in a vaulter’s training plan (de Villarreal, Requena, & Newton, 2010). Hadi et al. (2012) recommend that heavy loads (80-100% 1RM) of the full snatch should be incorporated into a training program to increase an athlete’s maximal strength. Canavan, Garrett, and Armstrong (1996) suggest that Olympic style weightlifting can improve intermuscular coordination and rate of force development capabilities, with the specific recommendation of hang snatches with a relatively light load (65% 1 RM) in order to maximise the dynamic correspondence in terms of velocity to vertical jumping. The way that altering the load affects velocity is explained by Kipp and Harris (2014) who state that as the amount of force an athlete can generate is limited, and as F=ma, then a reduction in the mass (m) being lifted will increase the athlete’s acceleration (a). Suchomel and Sole (2017) take this point further and suggest that the percentage of 1RM can be manipulated to elicit different adaptations, depending on which part of the load-velocity curve is being targeted by the training. Similarly Kossow and Ebben (2018) recommend different plyometric exercises, depending on the desired training adaptation. Therefore all of the above weightlifting and plyometric variations can find a place as part of a well-rounded yearly training program, in fact de Villarreal et al. (2010) state that a combination of weight training and plyometrics is more beneficial than only using one modality. The different exercises should be prescribed depending on the training goal at the time (Kossow & Ebben, 2018; Suchomel & Sole, 2017).
It is beyond the scope of this essay to explore different periodisation models, but as an example a vaulter aiming to peak for an indoor and an outdoor season could use the full snatch to increase maximum strength during the off-season, general preparation phase. Following this, during a period of specific preparation, the hang snatch and plyometric bounding activities could be used to maintain strength levels and maximise dynamic correspondence in terms of eccentric and horizontal forces, use of the stretch-shortening cycle and movement velocities, as described previously. During the break between the indoor and outdoor seasons the full snatch could again be used, before reverting to the hang snatch, the hang power snatch and plyometric activities during the outdoor competition period. In this example the athlete would be using exercises with a fairly high degree of dynamic correspondence throughout the year, in order to ensure appropriate and targeted motor system adaptations, with the level of correspondence/sports specificity increasing during competition periods.
In conclusion, this essay has not looked at the actions of the upper limbs or trunk in the snatch or pole vault take-off, but in the lower limb actions which were explored there has been a high degree of dynamic correspondence between the two skills and as such the snatch exercise can find a place in a pole vaulter’s training plan. The match has not been perfect though, and other exercises such as the hang snatch or plyometric activities may exhibit a higher degree of specificity.
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