Physical Training May 2012

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Department of Physical Education and Sport Sciences Serres

Aristotle University of Thessaloniki, Greece

Address correspondence to
Dr. Ioannis Gissis
Assist. Professor
Aristotle University of Thessaloniki
Department of Physical Education and Sport Sciences, Serres
Agios Ioannis, 62110 Serres, Greece
e-mail: igkisis@phed-sr.auth.gr

Abstract

The purpose of the present study was the evaluation of jump ability on a specially constructed force sledge machine, compared to different fall height and use of additional weight. The subject was 10 students of Physical education and sport sciences department, age 21±0,8 years old, weight 79±2,4 kg and height 1.78± 0,12cm. For the recording of data used, a) a force plate with piezoelectric crystals, type Kistler 9281 C, and b) construction of a ramp. The Subject performed vertical jumps Drop Jump (DJ), Squat Jump (SJ) and Counter Movement Jump (CMJ) from different height, initially only with body weight and then using additional weight. The dynamic analysis of the data was made using the software APAS XP and the statistical analysis was performed using the statistical method of repeated measures ANOVA and Tukey Post-Hoc test. Our results showed a statistically significant difference between selected variables and more specifically the placement of excess weight significantly affect the maximum force applied by the Subjects in all kinds of jumps performed whatever the drop height, and specifically in SJ, DJ40 and DJ120. Also in some situations seem to affect the average momentum, the touch time and the average work produced. In conclusion the combination of drop height and weight is a major determinant of jumping ability

Keywords: Vertical jump, Drop Jump, jumping ability, Counter Movement Jump, sledge machine

Introduction

The execution of a vertical jump is one of the key tests used to measure and evaluate the jumping ability of the athletes; the main goal is tested to produce the maximum power in a shorter time. This results in obtaining the maximum vertical speed, and achieving the maximum height, which can reach the center of gravity of the body being tested. The literature suggests a specific set of performance testers vertical jump, which is the indicator of the jumping ability of the test (Garcia-lopez et al., 2005). This test package consists of the vertical jump from a standing position without swinging arms and the knees flexed 90° [Squat Jump (SJ)], the vertical jump with counter movement without swinging arms and upright [Counter Movement Jump (CMJ)] and the vertical jump performed after the body drop from a specific height [Drop Jump (DJ)], (Komi & Bosco, 1979; Bosco et al., 1982; Vobbert et al., 1996; Chou et al, 2001; Kubo et al., 2007; Liu et al., 2009; Pereira et al., 2009; Korff et al., 2009; Lazaridis et al., 2010).

A stretch-shortening cycle (SSC) can be defined as an active stretch (eccentric contraction) of a muscle followed by an immediate shortening (concentric contraction) of that same muscle (Komi & Bosco, 1979). In human skeletal muscle SSC gives unique possibilities to study normal and fatigued muscle function and it’s found in most sports. Although explosive power has been extensively studied in lower body activities such as vertical jumping (Asmussen & Bonde-Petersen, 1974; Bosco & Komi, 1979; Bosco et al., 1982; Young & Bilby, 1993; Tsatalas et al., 2010).

A reliable way of evaluating the vertical jump (drop jumps and rebound jumps) in cases which it is not possible the execution of simple form, or to prevent injury or due to a high level of difficulty, it can be used a construction ramp force Sledge machine (SLM), where the subjects can perform bouts of jumps in a seated position, ensuring the stability and the balance of the body including the joints of the hip, knee and ankle, and achieve safe jumps without risk of injury. Also facilitates setting the height of fall, setting the angle needed to perform the jump as well as putting extra weight.

In literature we can see that these structures were used to facilitate the procedures when the drop height was large enough, (Galindo et al., 2009; Hoffrén et al., 2007; Sousa et al., 2007), also had to be performed when jumping with an extra large load, (Kubo et al., 2007; Comyns et al., 2007) but also when there was a great combination of drop and add a large load in the execution of jumps (Horita et al., 1999). Even to avoid injuries in the performance jumps after fatigue protocols (Regueme et al., 2007; Kuitunen et al., 2007), to perform jumps with only one end (Flanagan et al., 2007), but jumps in  people during rehabilitation from injury (Flanagan et al., 2008).  There are several reports in the literature relating to investigations in which we studied the jumping ability and muscle function in relation to the drop height and the use of additional weight (Gissis et al., 2003; Gissis et al., 2004), through various situations jumps, in which we find the use of ramp construction. The purpose of this study was to examine the effect of the fall of the extra weight on selected parameters on the reactive capacity in sledge machine built for this purpose.

Methods

Subjects

Ten healthy male students (age =23,5±0,71 years; body weight =84,34±5,63 kg; height =176±5,3 cm) with no history of neurological injuries or diseases, gave written consent to participate in this study. None of the participants had engaged in systematic strength training in the 6 months before the experiments began, but some were active in recreational sports. Approval for the project was obtained from the committee on human research at the Aristotle University of Thessaloniki. All procedures used in this study were in conformity with the Declaration of Helsinki.

Sledge apparatus

The execution of jumps took place in sledge apparatus comprising by a support base, a body construction, height adjustable arms, sliding rails, the seat and the force platform. The entire system is made of sheet metal. At the bottom is the support base, which is a lattice of iron and builds the system. The body structure is made of sheet metal. In the rear underside of the arms are set, that allow us to regulate the height of fall, and the angle of fall. Along the upper surface there are two rails, sliding rails, where the seat which use four wheel moves over them. There are seat belts for the attachment of the subject and mechanisms for placing extra weight. At the ends of leads in the movement of the seat is mounted a force plate, with piezoelectric crystals, Kistler 9281C, with sampling frequency 1000 Hz, for recording and evaluation of desired variables forces.

Picture 1. Sledge apparatus

Table 1. Mechanical properties of the sledge apparatus: m = mass of investigational and mass of the seat, Fg = gravitational force, Fab =Force of slide, Fn = downforce system, Fr = friction, S1 = initial position, S2 = final position, ds = S1-S2 = range of motion, dh = H1-H2 = drop height,  a = angle of plane

Dynamometer

For measuring ground reaction forces used a force plate of KISTLER (Type 9281 C), which was equipped with 4 piezoelectric transducers. The electric charge (pC) produced by the piezoelectric transducers 4, in acting on them some mechanical cause (pressure), went through a coaxial cable (Type: 1681V5), length of 5m, to load an amplifier (Type: 5233 A) where enhanced and converted to analogue voltage (Volt). Then the analog signal is digitized, card through a conversion of analog signals into digital (ARIEL Analog / Digital input - 16 A / D Channels) and recorded in a computer. The sampling frequency when recording forces were at 1000 Hz. Because the power askoutan for some time through force platform recorded the course of ground reaction force in relation to time (manual KISTLER). From the graph of the change of power in relation to time, could then be calculated through integration of the impetus used to train in specific intervals. Evaluated the vertical reaction force and then followed treatment of Fz than a year, with software program (Microsoft Excell) specifically designed to evaluate the momentum, work and time support, and variables.

Table 2. Variables

	SJ	CMJ	DJ40	DJ80	DJ120
Maximal Force	fmaxsj1	fmaxcmj1	fmaxdj40	fmaxdj80	fmaxdj120
Time of eccentric phase	tarnsj1	tarncmj1	tarndj40	tarndj80	tarndj120
Time of concentric phase	t8etsj1	t8etcmj1	t8etdj40	t8etdj80	t8etdj120
Touch time	synstsj1	synstcmj1	synstdj4	synstdj8	synstd120
Velocity of eccentric phase	varnsj1	varncmj1	varndj40	varndj80	varndj120
Velocity of concentric phase	v8etsj1	v8etcmj1	v8etdj40	v8etdj80	v8etdj120
Momentum of eccentric phase	parnsj1	parncmj1	parndj40	parndj80	parndj120
Momentum of concentric phase	p8etsj1	p8etcmj1	p8etdj40	p8etdj80	p8etdj120
Momentum mean	pmosj1	pmocmj1	pmodj40	pmodj80	pmodj120
Maximal Momentum	pmaxsj1	pmaxcmj1	pmaxdj40	pmaxdj80	pmaxdj120
Maximal Height	Ηeigsj1	Ηeigcmj1	Ηeigdj40	Ηeigdj80	Ηeigdj120
Work of eccentric phase	warnsj1	warncmj1	warndj40	warndj80	warndj120
Work of concentric phase	w8etsj1	w8etcmj1	w8etdj40	w8etdj80	w8etdj120
Work mean	wmosj1	wmoscmj1	wmosdj40	wmosdj80	wmosdj120

Test Protocol

The tests performed in jumps without compliant motion (SJ) and jumps with compliant motion (CMJ) a) without the extra weight placement, b) by placing 1/3 the weight of the tested c) deposit of 1 / 2 the weight of the investigational, d) by placing 1/1 by weight of the investigational. Also depth jumps (DJ) from a height of 40cm, 80cm, and 120cm, a) without the extra weight placement, b) by placing 1/3 the weight of an investigational, c) by placing 1/2 the weight of the investigational, d) placement of 1/1 by weight of the investigational.

Procedure

The process of measuring each test during the course of the measurement was wearing slacks and sneakers athletics. For increasing neuromuscular preparation and a minimization of the likelihood of injury the subject follow a warm up and stretching exercises and exercises in cycle ergometer. During jumps subjects were in sitting position and seat belted in the special of the SLM. Their hands were crossed at waist or chest to avoid any involvement, legs were stretched during the fall and in contact with the force platform. Originally performed in three successive attempts by jumping ramps compliant motion without (SJ) jumps submissive movement (CMJ) and depth jump (DJ) from a height of 40cm, 80cm, 120cm and without placing extra weight, then followed the same cycle other jumps three times once by adding 1/3 the weight of the body being tested a second time by placing an extra 1/2 the weight of the body being tested, and finally by placing 1/1 body weight of the investigational. Between the jumps were 2 breaks to avoid fatigue phenomena and the entire test were monitored by experts who guided them strictly.

Statistical analysis

The review concerns the comparison between groups was carried out by using the statistical package SPSS 15.Initially, descriptive statistics methods were used, to calculated average, standard deviation and standard error of the mean and the subsequent statistical inference methods. To examine the differences between the jumps on the selected variables using the method of repeated measures ANOVA. To examine the significance of differences in averages between time and groups will use the Tukey Post-Hoc test. Differences between variables will be tested at significance level p ≤ .0.5.

Results

SJ			CMJ
Variable	Mean	Std. Deviation	Variable	Mean	Std. Deviation
FMAXSJ1	1220,41	243,20
FM12SJ1	1566,21	199,00
FM12SJ1	1584,85	265,37
FM11SJ1	1597,74	245,48
			PMOCMJ1	648,26	1608,97
			PM12CMJ1	1914,74	1568,76
WMOSJ1	7019,00	840,00	WMOSCMJ1	1508,20	2407,80
WM12SJ1	12892,00	1182,00	WM12CMJ1	3083,80	2886,18
T812SJ1	410,10	149,7	T812CMJ1	466,20	115,96
T811SJ1	360,60	103,69	T811CMJ1	385,30	122,78

DJ40			DJ80			DJ120
Variable	Mean	Std. Deviation	Variable	Mean	Std. Deviation	Variable	Mean	Std. Deviation
FMAXDJ40	999,62	324,61				FMAXDJ12	1921,62	583,05
FM12DJ40	1297,33	452,78				FM12DJ12	2767,21	1211,80
FM12DJ40	1605,62	504,60				FM12DJ12	2507,43	551,03
FM11DJ40	1441,62	309,84				FM11DJ12	2402,97	277,47
PMAXDJ40	3253,17	3026,44	PMA12DJ8	1209,87	209,25	PMA12D12	1287,81	203,70
PMA12DJ4	8779,53	1588,18	PMA11DJ8	3264,62	273,52	PMA11D12	3459,29	289,11
PMA12DJ4	3839,63	4738,89				PM11DJ12	806,28	665,35
PMA11DJ4	2892,44	3599,79				PM12DJ12	3561,03	394,69
WMOSDJ40	1097,45	800,09				WM11DJ12	1674,62	1403,29
WM12DJ40	3350,56	763,52				WM12DJ12	637,01	759,12
WM12DJ40	1896,37	2621,49
HEIGDJ40	11406,00	1447,55				HE12DJ12	103,21	195,51
HE12DJ40	100,60	2765,04				HE12DJ12	174,39	232,01
HE12DJ40	724,76	1094,80				HE11DJ12	364,88	312,20
HE11DJ40	970,53	1550,20

Table 3. Results

Test results SJ. 

The maximum output power in this test case with body weight varies in al1/2 l cases adding extra weight which increases almost the same. The analysis of variance showed a significant difference in peak vertical jump power (F_3,27= 6,24, p = 0,002). We observe the increase in average total work during the 1/2 add extra weight. The analysis of variance showed a significant difference in overall project vertical jump free time (F_3,27 = 2,105, p = 0,123). The touch time in this test varies only between cases add 1/2 and 1/1 extra weight. The analysis of variance showed a significant difference in touch time of the vertical jump with no direction (F_3,27= 0,507, p = 0,680).

Test results CMJ. 

We observe that in this test the average power increases and varies significantly between cases free of charge and adding 1/2 of body weight. The analysis of variance showed a significant difference in the average momentum effect of the vertical with a submissive motion (F_3,27= 1,184, p = 0,334). The touch time in this test varies only between cases add 1/2 and 1/1 extra weight. The analysis of variance showed a significant difference in touch time the vertical motion with a submissive (F_3,27= 2,901, p = 0,053). We also observe an increase in the average total work by adding ½ extra weights. The analysis of variance showed a significant difference in average total project compliant with the vertical motion (F_3,27= 0,870, p = 0,469).

Test results DJ40. 

The maximum output power in this test is different in all cases add further weight to that increase. The analysis of variance showed a significant difference in average maximum power in jumping depth of 40 cm (F_3,27 = 7,430, p = 0,001). We observe that in this test the average momentum increases and varies considerably between cases, with the largest increase in case of adding 1/2 extra weight. The analysis of variance showed a significant difference in average power jump depth of 40 cm (F_3,27 = 3,846, p = 0,021. Observe the increase in average total work when adding additional ½ body weight in relation to other cases. The analysis of variance showed a significant difference in average total work, jumping from 40 cm depth (F_3,27= 4,351, p = 0,013). The touch time in this test varies with a large increase in case we add 1/2 extra weight in relation to other cases. The analysis of variance showed a significant difference in average touch time jumping from 40 cm depth (F_3,27 = 4,112, p = 0,016).

Test results DJ80. 

We observe that in this test the average momentum increases and varies significantly between cases by adding 1/2 and 1/1 body weight with the second being increased. The analysis of variance showed a significant difference in average power jump depth of 80 cm (F_3,27 = 1,508, p = 0,235).

Test results DJ120. 

The maximum output power in this test is different in all cases add further weight to that increase. The analysis of variance showed a significant difference in average maximum power in jumping depth of 120 cm (F_3,27 = 2,551, p = 0,077). We observe that in this test the average momentum increases and varies considerably between cases, with the largest increase in cases add 1/2 and 1/1 extra weight. The analysis of variance showed a significant difference in average power jump depth of 120 cm F (3,27) = 1,067, p = 0,379. Observe the increase in average total work during the addition of 1/1 extra weight. The analysis of variance showed a significant difference in average total work, jumping from 40 cm depth (F_3,27 = 1,364, p = 0,274). The touch time in this test varies with a large increase in case we add 1/1 extra body weight in relation to other cases. The analysis of variance showed a significant difference in average touch time, jumping from 40 cm depth (F_3,27 = 2,138, p = 0,119).

Discussion

Gollhofer et al. (1991) used vertical jumps DJ24, DJ40, DJ56, SJ, CMJ, to study the force length relationship of muscle tendon cluster and he argued that during the contact to the ground after the execution of jumps, the largest amount of power transferred to the conflict bone and a very small percentage is absorbed by tendons. Sheppard et al. (2009) studied the relationship of strength and anthropometric characteristics of athletes jumping ability in volleyball, using specific vertical jumps and variations. Korff et al. (2009) used CMJ to evaluate the strength of the legs of different ages in children.

Avela et al. (1998) studied the effect on muscle performance which was the interaction between the stimulus-response interval in the stretch shortening cycle of muscle elasticity with similar construction. In this survey, drop jumps were carried out from different heights and angle 30^o.  Kamibayashi et al. (2006), used a similar structure to examine the degree of change in the reflex response to the phase of pre-activation and activation of the muscles of the ankle during the landing on different types of surface on which jumps were carried out to a different surface soft and hard landing. 

Kubo et al. (2007) also used these structures to perform jumps SJ, CMJ and DJ for the evaluation of the effect with specific protocols, eccentric training and resistance training in muscle function and mechanical characteristics during the execution of jumps.

The high activation of the muscles of the legs to support the first phase (eccentric phase) depends with the production of elastic energy and greater muscle stiffness. Elastic energy is released in contraction increasing strength in concentric phase. The muscular system shows to be prepared for large charges stretch, and naturally high muscle activity in the eccentric phase. It has been shown that myotatic reflexes increase by increasing stretching speed (Viitasalo et al., 1998).
During the execution of consecutive jumps, the mechanical strength and the level of activation of soleus muscle is growing as increasing the time of support (Voigt et al., 1998). The stiffness of the lower extremities affects the transfer of elastic energy in a stretch - shortening cycle (Avela & Komi, 1998). The high activation of the muscles of the legs in the execution of vertical jumps creates changes in stiffness of the legs, while it increases the cause for the occurrence of peak vertical reaction forces (Zaggelidis & Lazaridis, 2011), vertical displacement and small support time (Nigg & Liu, 1999). The jump height increases with drop height, and this is due to the amount of energy stored in elastic elements of the muscle tendon system, (Asmussen, & Bonde-Petersen, 1974; Zamparo et al., 2000; Kubo et al., 2007; Galindo et al., 2009). 

Asmussen and Bonde-Petersen (1974), to explain the fact yield reductions by increasing the drop height above the ideal, attributed to the activation of reflexes, because the Golgi complex, irritated by excessive muscular forces. Katschajov et al. (1975) argue that in a good coaching point is to use various different drop heights to find the ¨perfect¨ drop height. To determine the ¨ideal¨ drop height, the vertical jumps under test is running, where the drop height ranges between 20 and 100cm.  The ¨ideal¨ drop height is the under test will achieve the maximum vertical displacement of the center of gravity of the body.

Komi and Bosco (1978) found that a jump after falling depth of 20-40cm high positive values ​​result in performance and the application of power. The vertical jump is performed at high speed take-off. Also jumping into a deep drop height after 40-60cm brings maximum positive and negative force in the vertical jump as well as performance. Schmidtbleicher and Gollhofer (1982), argue that the diversification of the jump height than is lower the height of fall, due to a differentiation of the technical implementation of the vertical jump. If the drop height increased, and the technique of jumping unchecked, the participants are likely to make greater downward movement at the time of landing.

A powerful and fast vertical jump depends on the height of fall, which was found from surveys ranging from 40 cm up to 60 cm and is related to the level of athletes (Komi & Bosco, 1978; Vitasalo, 1982; Hoffrén et al., 2007; Galindo et al., 2009). Also the different drop height seems to affect the function of agonist muscles, since behave differently when it increases (Sousa et al., 2007). Putting extra weight affecting the maximum force (Fmax) applied by the Subjects in all kinds of jumps performed whatever the drop height, and specifically in SJ, DJ40 and DJ120. This means that adding weight significantly enhances the stretch shortening cycle, resulting in increased muscle hardness and result in improved performance (Comyns et al., 2007). Also in some situations seem to affect the average momentum, the years of support and the average work produced from the above that the combination of fall and weight is a determining factor with no apparent effect on the characteristics of jumping ability. In conclusion, the evaluation of vertical jumps can be accomplished through implementation of different conditions through increasing the intensity by adding extra weight or by helping to reduce body weight.

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