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ABSTRACT
The purpose of
this study is to investigate the influence of the upper limb segment
loading on the throwing velocity of novice handball players during
the training and detraining period. After a familiarization period
for handball throwing, 21 players were examined during a 10-week
training period, followed by a 10-week detraining period. Loads were
applied on the arm and forearm resulting to an additional loading of
20% of the ball mass around the shoulder joint. Measurements of the
ball velocity were assessed with a radar gun with and without the
external loads. The results showed that the throwing velocity with
loaded limbs was lower only up to the 5th
week of training and this difference was diminished after 10 weeks of
training with loads. This adaptation was retained after 5 weeks of
detraining and recovered after 10 weeks of detraining. The above
mentioned changes are attributed mainly to neural and biomechanical
factors that affect the activation of the agonist and antagonist
muscles during throwing, taking into consideration the proprioceptive
feedback. In conclusion it is suggested that loading the upper limb
(a) may prohibit a high rate of decrement in throwing velocity
without loads during the detraining period and (b) may be an
efficient and safe method of training with many advantages compared
to other methods.
Key words: throwing velocity, handball, external loads, training, detraining
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Throwing is a basic ability of humans which is expressed from the early stages of development (Schmitt and Churchill 2003). Nowadays, the improvement of throwing skill is one of the main objectives in many sports, such as baseball, javelin, handball and others. During the last century several training methods have been established in order to achieve higher ball speed release. Concerning handball – and in part other relevant sports – it has been suggested that weight training results an improvement in throwing ball performance (Hoff and Almasbakk 1995, Walace and Cardinale 1997, Gorostiaga et al. 1999). Furthermore, plyometric training (Fritzsche 1977, Newman 1985, Miller 1987, Radcliffe 1990) and usage of lighter or heavier balls (Vasiliev 1983, van Muijen et al. 1991) or combinations of the above (Hoff and Almasbakk 1995) also showed beneficial results. Reviewing the current literature there is no clear evidence which method is more advantageous and why (for a recent and detailed review see van den Tillaar and Ettema 2004).
A new method for handball throwing training has been recently suggested (Kotzamanidis et al. 2003). This method has shown to be beneficial for novice handball players and concerns the loading of the segments of the upper limb during throwing training. The loads applied to the forearm and the arm of the players responded to the respective additional moment that a 20% heavier ball would induce around the shoulder joint. The principle of this training method is not new (Bosco et al. 1986, Ropret et al. 1998): by increasing the inertia of the limb, higher moments are applied around the joints and the respective muscles have to compensate to this additional load. However, the exact mechanisms which are responsible for the performance improvement are not clear. In general, it has been postulated that the central nervous system compensates the increased inertia by modulating the characteristics of the muscle activation in such way as to fulfill the desired goal (Cooke and Brown 1994, Gottlieb 1996, Pfann et al. 1998, Hatzitaki and McKinley 2001)
The advantage of this method is the maintenance of movement specificity during the training, i.e. the movement pattern performed during training is very close to the competition throwing movement. Furthermore, unlike the usage of heavier balls as a training method (van Muijen et al. 1991), training with loaded limbs permits specific to the player loading, the load can be applied for a longer period, for example, when the player does not possess the ball. As a final point, it should be mentioned that training with heavier balls does not permit application of this method under competitive conditions since it may become dangerous for the goal-keeper, which is not the case for training with loaded limbs. The importance of the later is more obvious if we consider that 75% of European handball goal-keepers experience elbow problems during their careers and 95% of these problems are related with elbow hyperextension when blocking the shot (Tyrdal and Bahr 1996).
However, it is still not clear what biomechanical influence that the weights might have on the joint kinematics and kinetics and the long term effects of such type of training. The present study was designed to examine the performance of novice handball players trained with loaded limbs with and without external loads. Furthermore, the performance of the players was evaluated during a detraining period in order to determine the maintenance of the training adaptations that occur.
Methods
Participants
Twenty-one
healthy, male students of the Department of Physical Education and
Sport Sciences of Thessaloniki participated voluntarily in the
present study. None of them had any previous experience with
systematic training involving throwing tasks. The age and the
anthropometric characteristics of the participants are shown in Table
1. The percentage of body fat was estimated
by measuring the skinfold thickness over the biceps femoris, rectus
femoris, abdominal and iliac (Durnin and
Womersley 1974). Informed consent was
obtained from each participant after content of the study was
explained in detail.
Table I. Age and anthropometric data of the participants (n=21).
|
|
mean |
standard deviation |
minimum |
maximum |
|
Age (years) |
19.1 |
0.9 |
18.0 |
21.0 |
|
Body mass (kg) |
75.2 |
8.5 |
59.0 |
93.0 |
|
Body fat (% of body mass) |
11.3 |
3.3 |
5.1 |
18.7 |
|
Body height (cm) |
181.1 |
6.8 |
168.5 |
191.5 |
Measurements
The duration of the experiment was in total 30 weeks. During the first 10 weeks familiarization of the participants was achieved. Each training session lasted from 50 to 75 minutes and was fully supervised. This included drills to learn and improve the technique of the handball throwing task using normal balls, without loads around the upper limb segments. After this period, a throwing training protocol was based on previous studies (DeRenne et al. 1994) concerning baseball and assessed as described in detail previously (Skoufas et al. 2003). In summary, each training session was performed 3 times a week and included 9-13 sets of 6 maximal throws using competition handballs (58 cm circumference and 425 g mass) and loaded forearm and arm with 84 and 107 g (Kotzamanidis et al. 2003). This load corresponded to the load that is induced by a 20% heavier ball around the shoulder joint. Taking into consideration anthropometric data from cadavers (Dempster 1955), the ratio of the forearm to arm mass remained constant with and without external loads.
The loads were constructed by elastic armbands filled with lead spherules and were fixed around the centre of mass of the forearm and arm. The weight was checked and calibrated before each training session. The armbands were fixed with Velcro straps approximately in the center of mass of each segment (Dempster 1955).
The player’s throwing speed was evaluated during the 5th and 10th week of training, followed by two additional tests with a 5 weeks interval during a 10 week detraining period. All measurements were assessed with and without loaded limbs. An additional measurement before the beginning of the training was assessed only without loaded limbs; maximal throws with loaded limb was threatening for skeletomuscular injuries and therefore were omitted.
The throwing speed of the ball was measured using a Doppler radar gun (Sports Radar 3300, Sports Electronics Inc.). The accuracy of the device was 0.1 km/h (0.03 m/s) for a field of 10 degrees wide, as defined by the manufacturer. The players were shooting at stance position, from a 6 meter distance against the radar gun, which was protected by a wooden disk (50 cm diameter) with a hole in the middle to allow visual contact between the measuring instrument and the ball. The shots that missed the wooden disk were not evaluated and the performance of each player was the average of 7 valid trials. This testing setup ensured measurements achieved within the 10 degrees valid field of the radar gun. Recordings of the arm velocity were recognized as invalid.
Statistics
Means and standard deviations were calculated for all dependent variables. For the statistical analysis the STATISTICA ® software was used. An one-way ANOVA for repeated measurements was assessed to calculate the mean differences between the three different measurements before training, during training and during detraining. The Scheffé post-hoc test was used to detect the existence of any differences between the groups or between the measurements. The alpha level was set at p<0.05.
Results
During and after the training period none of the participants expressed any complaints about pain in the throwing upper limb.
The one-way ANOVA revealed that the throwing ball velocity was differentiated during the experiment when measured with (F3,20=127.6, p<0.001) and without external weights (F4,20=38.3, p<0.001). The handball throwing velocity with loaded limbs appeared to be lower after 5 weeks of training compared to the throwing velocity without loading (Figure 1). However, this difference was not statistically significant after 10 weeks of training with loaded limbs. More specifically and as shown in Figure 2, throwing velocity with loaded limbs was 12.4±4.3% (p<0.01) and 2.2±2.2% (p>0.05) lower during the 5th and 10th week of training, respectively. Five weeks after detraining the difference between the two throwing modi was minimal (0.3±2.9%, p>0.05), whereas after 10 weeks of detraining the difference increased significantly (9.4±3.9%, p<0.01).
Figure 1. Mean values and standard deviation of mean for the throwing velocity with and without upper limb loading, after 5 and 10 weeks of training and detraining. Asterisks designate significant differences between the two modes of throwing (p<0.01).
Figure 2. Percentile differentiation between measurements with and without upper limb loading during 5 and 10 weeks of training and detraining. Asterisks designate differences between the measurements (p<0.01).
Discussion
Training with loaded limbs improved the throwing performance of novice handball players. This improvement was present either with or without the application of loads over the arm and forearm. Loading the segments of the throwing arm increases the resistance and the work that the muscles have to produce in order to achieve the required acceleration. Therefore it would be expected that the throwing performance should be lower when segments are loaded. Although the mean throwing ball speed was in general higher when shooting without loads, this difference reached the significance level only during the 5th week of training; during the end of the training protocol (10th week) and detraining this difference was diminished until the 10th week of detraining.
As mentioned above, the load over the upper limbs increases the inertia of the respective segments and the inertia moments around the joints. This implies that the muscles involved in the throwing task are strained to overcome this resistance (Cooke and Brown 1994, Gottlieb 1996, Pfann et al. 1998). As a result, the nervous system activates the relevant muscles more intensely and this leads to the adaptations observed in the present study. There are several alternatives to explain these adaptations, such as selective activation of fast twitch motor units (Smith et al. 1980) and/or reduced co activation of the antagonists (Sale 1992).
Interestingly, after 10 weeks of training no differentiation between throwing with and without weights were observed. For this paradox there are two possible explanations, without one excluding the other: Firstly, training with weights possibly modified the technique of the players who finally adapted to the new situation (with weights). Consequently, shooting without weights is probably a new uncommon condition that requires a certain amount of time to become accustomed to. This is supported by the fact that during detraining the performance in shooting without weights was retained, which was not the case when shooting with weights. It seems therefore that the absence of the training stimulus (training with external loads) “recovered” the ability of shooting without external loads. Secondly, it could be assumed that the increased inertia of the segments that are loaded may be beneficial at the final outcome of the throw. Once a proximal segment is accelerated, the energy transferred to the more distal segment is bigger due to the increased inertia. If the movement is well coordinated this could result even a better performance compared to shooting without weights. It seems that the first 5 weeks of training were not enough to achieve this goal. However, after the 10th week the performance of shooting with or without external loads was very similar (~2% difference).
One of the most important findings of the present study is the fact that throwing velocity without weights did not fall directly after the end of the training but followed a rather slow rate of decrement. This could be an important advantage for players that have to stay out of court (due to injury for example) for a longer period.
It has been suggested that excessive elbow valgus moments during baseball pitching might be responsible for the frequently reported elbow injuries in throwers (Wilson et al. 1993). According to kinematic data based on baseball pitchers, there are four factors that are responsible for 97% of the variance in elbow valgus stress (Werner et al. 2002): the shoulder abduction angle at the stride foot contact, the peak shoulder horizontal adduction angular velocity, the elbow angle at the instant of peak valgus stress and the peak shoulder external rotation torque. Interestingly the authors, based on their data, suggest that excessive valgus elbow stress is moderated when the elbow is more flexed. This lead to a greater external shoulder rotation torque which is also reducing the elbow valgus moment. The application of external load over the forearm may contribute to this additional external shoulder rotation, which might also be beneficial for the throwing performance in terms of ball speed (Sabick et al. 2004). The later argument is based on the fact that increased external shoulder rotation offers a greater arc over which the ball can be accelerated.
However, the usage of external loads on the upper limbs during throwing training raises concerns about injuries induced by increased moments applied around the joints. A recent study on baseball players showed that the external shoulder rotation is increased after long-term throwing training and this increase was greater for older players (Mair et al. 2004). This may induce humeral deformation, a characteristic finding that is observed even in paleolithic fossils of humans that intensively used spears for hunting (Schmitt and Churchill 2003). Excessive valgus external moments around the elbow joint which occur during throwing may induce peripheral nerve injury, as shown by the decreased ulnar nerve conduction velocity observed in injured elbows of baseball pitchers (Wei et al. 2005). Therefore, loading of the upper limbs with higher weights should be decided with wariness.
Concerning the non-throwing arm, it has been shown that limited movement is a characteristic of skilled baseball throwers (Murata 2001). Furthermore, the same study supports that the faster the ball speed, the more limited the movement of the non-throwing arm. This movement limitation could be achieved by application of external loads, increasing the inertia of the segments. However, the effect of such an intervention has to be examined in detail.
In conclusion, training with loaded limbs was beneficial to the throwing ball velocity of novice handball players and during the training period the difference in performance shooting with and without loads was minimized. This was attributed either to neural and/or biomechanical factors. Furthermore, training with loads preserved high performance shooting without loads during the detraining period. This fact, which requires further investigation to be clarified, may be valuable for handball players after planned (vacations) or unplanned (injury) detraining periods.
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