Re: Knee Angle In Counter Movement Jumps Testing

[Guest guest]

>

> Hi there,

>

> When using power measures such as gymaware etc, does anybody know of any

studies or what is your experience with regards optimal knee angle when testing

for optimal power output with counter movement jumps?

>

> I would imagine that it may be different depending on loads etc but would

welcome any discussion?

>

> Ideally I would like evidence on both single leg and bilateral if anyone knows

of any out there or what you use if applicable?

>

The below extracts may be relevant (Bosco, 1998):

Conflicting results like the ones presented by Bernes and colleagues (1992) in

which the average SJ performance was 42.1 cm, even higher than CMJ performance

(41.9 cm). The most relevant point is that this authors interpreted these

results as lack of elastic capacity in an entire soccer team!!!

Unfortunately, sometimes results reported in the literature can be misleading

and without any relation with the biological processes involved. In fact, it is

not plausible that human skeletal muscle is not able to reuse elastic energy. In

the literature there are many experimental evidences on this phenomenon (see

Cavagna, 1977; Goubel and Marini, 1987). The lack of difference between CMJ and

SJ was without any doubt due to an erroneous testing technique. If the test

protocol is not rigidly observed, results are not valid. For example, if SJ is

performed with a minimum counter movement, this can greatly enhances performance

through reuse of elastic energy.

Therefore, performance would not be only produced by the contractile elements

but also with elastic energy contribution. Furthermore, it is necessary to

carefully control knee angle during CMJ because this can greatly influence test

results. Often weak and slow subjects do not bend enough the knees during the

counter movement (Bosco, 1978). Knee angle should be around 90 deg but without a

learning period it is not easy for most of the subjects to obtain this value.

If legs are not fully bent, during the pushing phase that follows prestretching

there will be less time to push and therefore a reduced net impulse and

performance in comparison to a correctly executed CMJ.

The possibility to train muscle elastic capacities with general and specific

exercises is well known but there are few experimental studies on this topic.

The first one was conducted by Bosco between 1976 and 1978 on. high level

Finnish male and Italian female volleyball players. Similar studies were

realised before in volleyball (Bosco and Pittera, 1975) and track and field

(Zanon, 1973a, 1974; Bosco, 1973, 1974; Locatelli, 1974-82) but training induced

changes were not scientifically analysed. After a training

period during which maximal strength training was substituted with plyometric

training, the Finnish, male volleyball players markedly improved their

performance in CMJ and SJ (p < 0.01) and a more modest increase in 5J

performance (Figure 82). On the contrary, the Italian female volleyball players

that were following a traditional training regimen (no plyometric exercises) did

not show any improvement (tab. 2) (Bosco et aI., 1979). The lack of improvement

of SJ in Finnish volleyball players could be interpreted as a lack of direct

stimuli on the contractile component of leg extensor muscles, while the marked

improvement in CMJ and DJ could be attributed to adaptations induced by specific

plyometric training.

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Carruthers

Wakefield, UK