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DETERMINANTS OF THEABILITIES TO JUMP HIGHERAND SHORTEN THECONTACT TIME IN ARUNNING

1-LEGGED VERTICAL JUMP IN BASKETBALLKEN MIURA, MASAYOSHI YAMAMOTO, HIROYUKI TAMAKI, AND KOJI ZUSHI

National Institute of Fitness and Sports in Kanoya, Kagoshima, Japan

ABSTRACT

Miura, K, Yamamoto, M, Tamaki, H, and Zushi, K. Determinants

of the abilities to jump higher and shorten the contact time in

a running 1-legged vertical jump in basketball. J Strength Cond

Res 24(1): 201206, 2010This study was conducted to

obtain useful information for developing training techniques for

the running 1-legged vertical jump in basketball (lay-up shotjump). The ability to perform the lay-up shot jump and various

basic jumps was measured by testing 19 male basketball

players. The basic jumps consisted of the 1-legged repeated

rebound jump, the 2-legged repeated rebound jump, and the

countermovement jump. Jumping height, contact time, and

jumping index (jumping height/contact time) were measured

and calculated using a contact mat/computer system that

recorded the contact and air times. The jumping index indicates

power. No significant correlation existed between the jumping

height andcontact time of the lay-up shot jump, the 2 components

of the lay-up shot jump index. As a result, jumping height and

contact time were found to be mutually independent abilities. Therelationships in contact time between the lay-up shot jump to the

1-legged repeated rebound jump and the 2-legged repeated

rebound jump were correlated on the same significance levels

(p , 0.05). A significant correlation for jumping height existed

between the 1-legged repeated rebound jump and the lay-up shot

jump (p , 0.05), although none existed for jumping height

between the lay-up shot jump and both the 2-legged repeated

rebound jump and countermovement jump. The lay-up shot index

correlated more strongly to the 1-legged repeated rebound jump

index (p , 0.01) when compared to the 2-legged repeated

rebound jump index (p , 0.05). These results suggest that the

1-legged repeated rebound jump is effective in improving both

contact time and jumping height in the lay-up shot jump.

KEY WORDS lay-up shot jump, 1-legged repeated rebound

jump, training technique

INTRODUCTION

In basketball, improving jumping abilities markedlyenhances individual competitive performance. In

basketball, players most often jump when shootingand rebounding. When shooting, a player must dribble

the ball while avoiding defenders and follow the rules ofbasketball without traveling, and then put the ball throughthe basket. Additionally, depending on defender actions, a

shooter must decide whether to jump with 1 or 2 legs. Themost common example of shooting with a 1-legged takeoff on

an approach run is to drive to the basket and shoot a lay-up;the most common example of shooting with a 2-leggedtakeoff on an approach run is to drive to the basket and shoot

a jump shot. A dunk may be performed with either a 1-legged

or a 2-legged takeoff. These jumping abilities involve jumpingheight and contact time. In competition, if an offensive player

can jump high and quickly, then this player is more likely todisrupt the timing of defenders (10), draw a foul, and shoot

the ball. When comparing running 1-legged and 2-leggedvertical jumps, there is no marked difference in jumpingheight, but a running 1-legged vertical jump has a shorter

contact time (16,21). In studies on the running 1-leggedvertical jump, there have been reports on the high jump andlong jump in track and field, but because people compete for

height and distance in these athletic events, there have notbeen many studies that analyzed contact time as 1 of the

factors determining jumping performance (2,13,14).

Any movement that exerts explosive power, such as therunning 1-legged vertical jump, is referred to as a ballistic

movement, and its neurological control mechanisms aredifferent from movements that take a relatively long time toexecute, such as the running 2-legged vertical jump in which

the knees are flexed deeply (6). Additionally, in the running1-legged vertical jump, motor unit mobilization and neurolog-

ical stimulation of muscles enable quick movements (9,17).From the viewpoint of muscle contraction, the running

1-legged vertical jump is a stretch-shortening cycle

Address correspondence to Ken Miura, [email protected].

24(1)/201206

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movement characterized by a high level of eccentric musclecontraction occurring immediately after landing, which is

immediately followed by concentric muscle contraction. Thestretch-shortening cycle facilitates the regulatory mechanism

of nerves, muscles, and tendons in terms of the stretch reflexmechanism (9) and elastic energy storage and reuse (1,4,5). It

exerts a large amount of force quickly from the beginning andimproves motor efficiency.

This information suggests that the running 1-legged verticaljump in basketball requires comprehensiveabilities to efficiently

carry out ballistic and stretch-shortening cycle movements.With the drop jump, in which a person jumps off of a stand,

lands, and then immediately jumps, and with the repeatedrebound jump, in which a person successively and quickly

jumps vertically (19,22), a basic jumping index that was

calculated based on contact time and jumping height (jumpingheight/contact time) has been used to assess ballistic stretch-

shortening cycle movements (23,24). Many studies on basketballplayers have analyzed jumping techniques (11,12,26), but there

have only been a few studies that measured a jumping index (3).In the present study, the aforementioned assessment

method was applied to assess the abilities to jump higherand shorten the contact time of the running 1-legged vertical

jump in an attempt to ascertain determination factors andefficacy. In addition, we compared basic jump performances,

in which the subjectwas asked to jump in different techniques,with the running 1-legged vertical jump performance. Thesebasic jumps were performed without an approach run and

were classified by the combination or 2-legged or 1-leggedtakeoff with deep or shallow knee bending. The hypotheseswere that a subjects ability to perform a running vertical jump

in basketball could be effectively assessed with the jumping

index; that there is a basic jump that is effective in improvingboth contact time and jumping height, the 2 components ofthe jumping index in the running 1-legged vertical jump; andthat the basic jump is a jumping technique resembling the

running 1-legged vertical jump motion.

METHODS

Experimental Approach to the Problem

Each subject was asked to perform several jumps: a lay-upshot jump (LSJ), in which the subject ran toward the basket

and jumped with a 1-legged takeoff for a basketball lay-upshot, and basic jumps in which the subject was asked to jump

in different ways. The types of basic jumps were counter-movement vertical jump (CMJ), 2-legged repeated rebound

jump (TRRJ), and 1-legged repeated rebound jump (ORRJ).

The independent variables in this study were maximumjumping height, contact time, and jumping index in LSJ. Thedependent variables in this study were maximum jumping

height; contact time (except for CMJ); and jumping index(except for CMJ) in CMJ, TRRJ, and ORRJ.

Subjects

Subjects were 19 male university basketball team players

who were selected to play in a national collegiate tournament(32 teams) in Japan in 2006. Their mean (6SD) height was176.9 6 7.0 cm, body weight was 68.9 6 7.3 kg, and age was

19.66 1.3 years. All subjects had played basketball for at least

5 years. The subjects volunteered to participate in this study.The subjects were tested after 1 week in a major collegiatetournament. No subjects were currently suffering any lower-

extremity injury that would prevent them from completingthe testing jumps. All subjects were informed of theexperimental risks and signed an informed consent documentprior to the investigation. This investigation was approved by

an Institutional Review Board for the use of human subjects.

Procedures

In LSJ, the subject was placed 6 m from the center of thebasket (height: 3.05 m) and was asked to take 2 steps and

jump with a 1-legged takeoff for a lay-up without the

basketball. In the present study, tests were conducted withoutthe basketball to eliminate various constraint conditions, andthis allowed the subjects to fully concentrate on jumping.

TABLE 1. Jump performances in LSJ, ORRJ, TRRJ,and CMJ (Mean 6 SD).*

Parameter Mean 6 SD

LSJLSJh (cm) 58.6 6 5.3LSJtc (ms) 217.5 6 19.7LSJindex (m/s) 2.715 6 0.4

ORRJORRJh (cm) 26.0 6 2.3ORRJtc (ms) 273.6 6 39.3ORRJindex (m/s) 0.974 6 0.2

TRRJTRRJh (cm) 43.6 6 5.4TRRJtc (ms) 177.6 6 20.7TRRJindex (m/s) 2.486 6 0.4

CMJCMJh (cm) 50.5 6 5.4

*Results of significant differences areas follows (n = 19).Jumping height: LSJ.CMJ.TRRJ.ORRJ (p , 0.001).Contact time: TRRJ,LSJ,ORRJ (p , 0.001).Jumping index: LSJ.TRRJ (p , 0.05),LSJ.ORRJ and TRRJ.ORRJ (p , 0.001).

LSJ = Lay-up shot jump; LSJh = jumping height forLSJ; LSJtc = Contact time for LSJ; LSJindex = jumpingindex for LSJ.

ORRJ = One-legged repeated rebound jump;ORRJh = jumping height for ORRJ; ORRJtc = Contacttime for ORRJ; ORRJindex = jumping index for ORRJ.

TRRJ = Two-leggedrepeated rebound jump; TRRJh =jumping height for TRRJ; TRRJtc = Contact time for TRRJ;TRRJindex = jumping index for TRRJ.

CMJ = Countermovement jump; CMJh = Jumpingheight for CMJ.

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Additionally,the subjects were asked to run toward the basketso that they could maximize their jumps (7,1315). All

subjects took off on the leg opposite from the hand used forshooting the basketball. The subjects were instructed to

imitate a lay-up and jump as high as possible.In basic jumps, the subjects

were askedto perform CMJ andrepeated rebound jumps (RRJ)(19,22). The CMJ was thevertical jump from an erect

standing position with a pre-liminary countermovement. In

this test, the subjects wereinstructed to jump as high aspossible. The RRJ were re-

peated vertical jumps with a re-bound movement similar to

bouncing a ball and wereperformed with 2 legs (TRRJ)

or 1 leg (ORRJ). In this test, thesubjects were instructed to

jump as fast and as high aspossible. Before measurements

were taken, the subjects suffi-ciently practiced these jumps.

Jumping heights and contacttimes (except for CMJ) weremeasured using a contact mat/

computer system (8,19,24). Ineach test, the subjects jumpedon a contact mat (66 3 100

cm). In LSJ, because takeoff and

landing sites markedly differed,2 mats were placed near thetakeoff site and 4 mats wereplaced near the landing site.

The contact mat/computersys-tem read the ON and OFFsignals during foot contact on

the ground and the flight of thebody in milliseconds. Contact,

takeoff, and landing times wererecorded to calculate contact

time (Tcon, sec) and air time(Tair, sec). The contact times

for TRRJ, ORRJ, and LSJ wereindicated as TRRJtc, ORRJtc,

and LSJtc, respectively. Jump-ing height was calculated using

the free-fall formula (H = 1/8 gTair2). Furthermore, g wasgravitational acceleration with

a value of 9.81 m/sec2. Thejumping heights for TRRJ,ORRJ, LSJ, and CMJ were

indicated as TRRJh, ORRJh, LSJh, and CMJh, respectively.Jumping index was calculated by dividing the jumping height

by the corresponding contact time (jumping height/contacttime) and indicates power. The jumping index for TRRJ, ORRJ,

and LSJ were indicated as TRRJindex, ORRJindex, and

Figure 1.Relationships among lay-up shot jump index (LSJindex), contact time (LSJtc), and jumping height (LSJh)

in lay-up shot jumps.


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LSJindex, respectively. Thesedata were immediately displayed

and feedback was provided aftereach trial. Tests were invalid if

the feet were off the mats.In LSJ and CMJ, 3 valid

measurements were taken anddata from the highest jumpswere used (19). In TRRJ andORRJ, the subjects swung their

arms to continuously perform5 repeated rebound jumps

(19,22) and each test was re-peated twice. From 10 measure-ments, the highest jumping

index was used for analysis (19).

Statistical Analyses

Numerical data were expressed

as mean6

SD. One-way anal-ysis of variance (ANOVA) wasused to compare data among

the different jumping tests.Items with significant Fvalueswere further subjected by Scheffe multiple comparisonanalysis. Pearson correlation analysis was used to compare

parameters. In all analyses, the level of significance was set atp, 0.05. The within-session reliability for each variable wascalculated with an intraclass correlation coefficient (LSJh,

R= 0.818; LSJtc,R= 0.886; LSJindex,R= 0.861; TRRJh,R=0.849; TRRJtc,R= 0.797; TRRJindex,R= 0.846; ORRJh,R=0.718; ORRJtc, R = 0.780; ORRJindex, R = 0.839; CMJh,

R= 0.928).

RESULTS

Comparison of LSJ, ORRJ, TRRJ, and CMJ Measurements

Table 1 lists the mean (6SD) for LSJ, ORRJ, TRRJ, and CMJ.The jumping height was the highest LSJh, followed by

CMJh, TRRJh, and ORRJh, in that order (p, 0.001). Thecontact time was the highest TRRJtc, followed by LSJtc andORRJtc, in that order (p , 0.001). The LSJindex wassignificantly greater than TRRJindex (p , 0.05), andORRJindex was significantly smaller than that LSJindex orTRRJindex (p, 0.001).

Interrelationships Among LSJindex, LSJtc, and LSJh

Figure 1 shows the interrelationships among LSJindex, LSJtc,

and LSJh. A significant correlation existed between LSJtcand LSJindex (r= 20.700,p, 0.001) and between LSJh andLSJindex (r = 0.678, p , 0.01). However, no significantcorrelation existed between LSJtc and LSJh (r= 0.041, ns).

Relationship of LSJ to ORRJ, TRRJ, and CMJ in Terms of

Jumping Index, Contact Time, and Jumping Height

Figure 2 shows the relationship of LSJ to ORRJ, TRRJ, andCMJ in terms of jumping index, contact time, and jumping

height. Regarding jumping index, a significant correlationexisted between ORRJindex and LSJindex (r = 0.614, p,0.01) and between TRRJindex and LSJindex (r= 0.509,p,0.05). Regarding contact time, a significant correlationexisted between ORRJtc and LSJtc (r = 0.472, p , 0.05)and between TRRJtc and LSJtc (r = 0.567, p , 0.05).Regarding jumping height, a significant correlation existed

between ORRJh and LSJh (r= 0.570,p, 0.05). However, no

significant correlation existed between TRRJh and LSJh (r=0.305, ns) or between CMJh and LSJh (r= 0.360, ns).

DISCUSSION

In the present study, we first compared LSJ, a typical running

1-legged vertical jump in basketball, to basic jumps that aregenerally used to assess jumping abilities (Table 1). The results

showed that the LSJh was significantly higher than those forthe basic jumps and the LSJindex was also significantlyhigher. Hence, LSJ was the jumping technique with the

highest jumping index. However, LSJtc was significantlylonger than that TRRJtc. Aura and Viitasalo reported thatthe average contact time for the high jump was 177 ms (2),

and Stefanyshyn and Nigg reported that the average contacttime for the long jump ranged from 150 to 170 ms (18). The

average LSJtc was 217.5 ms in the present study, whichwas shorter when compared to past study results of 230 to250 ms (18).

The lay-up shot jump index (LSJindex) is a parameter thatis calculated based on the contact time (LSJtc) and jumping

height (LSJh) of LSJ. As shown in Figure 1, a significantcorrelation existed between LSJindex and LSJtc and betweenLSJindex and LSJh. However, no significant correlation

Figure 2. Relationship of lay-up shot jump index (LSJindex) to 1-legged repeated rebound jump index (ORRJindex)

and 2-legged repeated rebound jump index (TRRJindex). Relationship of contact time (LSJtc) to ORRJtc and

TRRJtc. Relationship of jumping height (LSJh) to ORRJh, TRRJh, and countermovement jump height (CMJh).



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existed between LSJtc and LSJh, thus confirming that these 2variables are mutually independent. These results show that

LSJtc represents the ability to shorten the muscle action andLSJh represents the ability to acquire the jumping height,

and, as a result, contact time and jumping height are mutuallyindependent abilities. Therefore, when examining LSJ, it is

important to separately analyze contact time and jumpingheight.

In the present study, LSJ was compared to basic jumps(ORRJ, TRRJ, and CMJ) in terms of jumping index, contact

time, and jumping height (Figure 2). The results showedthat LSJindex correlated more closely to ORRJindex than

TRRJindex, but LSJtc correlated more closely to TRRJtcthen ORRJtc. Furthermore, a significant correlation was seenin jumping height between ORRJh and LSJh, but not

between LSJh and TRRJh or between LSJh and CMJh.The 2-legged drop jump is a typical reactive strength

movement, and this jump is important for improving therunning 1-legged vertical jump and assessing jumping abilities

(25). The present study clarified that TRRJ is a trainingtechnique that is effective in improving LSJtc. However,LSJindex correlated more closely to ORRJindex thanTRRJindex and no significant correlation existed between

TRRJh and LSJh. The reason for this was that both ORRJand LSJ required subjects to jump with 1 leg, and when

compared to TRRJ, ORRJ more closely resembled LSJ interms of movement characteristics. In addition, no significantcorrelation existed between CMJh and LSJh, and the reason

for this was that CMJ was a low-intensity movement witha low stretch-shortening cycle, whereas LSJ was a ballistichigh-intensity movement with a high stretch-shortening

cycle. This suggests that effective training must follow the

principle of specificity.Furthermore, a significant positive relationship existed

between ORRJ and LSJ in terms of contact time and jumpingheight. This indicates that people with quick ORRJ also have

quick LSJ and those with high ORRJ height have high LSJheight. Aura and Viitasalo compared the 1-legged drop jump(ODJ) and high jump and reported that because the 2 jumps

had different contact times, ODJ was not suited for high jumptraining (2). When compared to high jump and ODJ, LS J and

ORRJ share more similarities: there is a significant correla-tion in contact time between LSJ and ORRJ, whereas both

high jump and LSJ are 1-legged jumping movements with anapproach run; the contact time for LSJ is longer; and the

contact time for a rebound jump is significantly shorter whencompared to a drop jump (22). Additionally, in the subject

with the shortest ORRJtc, the difference between ORRJtcand LSJtc was small (17 ms). These findings suggest that

ORRJ is the most effective technique that can improve bothcontact time and jumping height for LSJ. Furthermore, in

vertical jump, the maximum flexion angles for the knee andhip joints for a 1-legged takeoff phase are greater whencompared to a 2-legged takeoff phase (20), thus suggestingthat the maximum flexion angles for the knee and hip joints

for ORRJ are greater when compared to TRRJ. Hence, TRRJ

with slight knee bending movements is suited for strength-ening the stiffness of the ankle joint (22) and compared to

TRRJ, ORRJ is a movement that more fully involves the kneeand hip joint muscles.

In the future,it will be necessary to shortenthe contact time

and improve the jumping height in LSJ and further analyzethe relationship of LSJ to ORRJ as a training technique.

PRACTICAL APPLICATIONS

The results confirmed that LSJindex is useful for assessing the

jumping ability of basketball players using a running 1-leggedvertical jump. The LSJ ability consists of 2 independent

factors: contact time and jumping height. Therefore, whenimproving LSJ, it is necessary to train to improve these2 factors. ORRJ was shown to be an effective basic jump

technique in improving both contact time and jumping heightin LSJ. These findings are useful for evaluating ability to

perform running 1-legged vertical jumps in basketball andexamining training techniques to improve ability to performrunning 1-legged vertical jumps in basketball.

ACKNOWLEDGMENTS

The authors would like to acknowledge funding support fromthe National Institute of Fitness and Sports in Kanoya. We

would also like to thank the athletes from the NationalInstitute of Fitness and Sports in Kanoya for participating in

this project.

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Miura et al 2010