INTERNATIONAL JOURNAL OF SPORT BIOMECHANICS, 1989, S, B9-98

Biomechanical Characteristicsof Jumping

Ossi Aura and Jukka T. Viitasalo

Four track and field athletes were subjects in a study that analyzed sevenjumping exercises and flop-style high jump takeoffs for ground reaction forces,knee angular kinematics, and electromyographic activities of knee extensormusculature. The ground contact times varied between 17713 (flop) and278 25 ms (standing five jumps). The peak ground contact forces were from5002 130 N (special dropjump) to 8202 901 N (running five hops). Aver-age knee angular velocities were highest in the eccentric phase of the floptakeoff (w=7.1 2.1 rad x s"'). Electromyographic activities before theground contact and during the eccentric phase of contact were highest in theflop-style high jump, while during the concentric phase of contact a specialdropjump exercise showed the highest activity. Preactivity IEMG correlatedwith the eccentric IEMG. force, and knee angular velocity positively andwith the contact time negatively (/KO.OOl). while eccentric IEMG correlatedwith the eccentric force and angular velocity positively and with the contacttime negatively (p

90 AURA AND VIITASALO

body weight was 78.8 2.7 kg. The best results for the high jumpers were 212 cm,214 cm, and 224 cm, and for the triple jumper it was 16.74 m.

The subjects performed several jumping exercises with maximal effort dur-ing the 2 days of experiments. The exercises consisted of standing five jumps(alternative foot contact, S5J), standing five hops (unilateral foot contact, S5H),running (four run-up steps) five jumps (R5J). running (six run-up steps) five hops(R5H, Figure Ia), hurdle hopping (HH, Figure lb), drop jumps with unilateralfoot contact (dropping height 52 cm, DJ, Figure Ic), drop jumps with unilateralfoot contact with two approaching steps (dropping height 52 cm, RDJ, Figure Id),and the flop-style bigh jump (flop. Figure le). The jumping drills were measuredduring the first day of the experiment, and the high jumping during the second day.

All the exercises were performed on a force platform system that consistedof five platforms measuring 170 x 80 cm, which were sensitive to vertical andhorizontal ground forces (for more details, see Komi, 1985). An electricalgoniometer (Elgon) was attached to the lateral side of the subject's left (takeoff)knee joint to register angular displacements during the exercises. The goniometer(weight 58 g) was constructed using a potentiometer fixed to a plastic rigid body(20 cm X 2 cm) and a rigid and light (20 g) iron stick (20 cm, 6 0.3 cm) thatwas fixed to the moving axis of the potentiometer. The rigid body was firmlyfixed to the lateral side of the left thigh, and the iron stick to the lateral side ofthe left calf, using plaster and rubber bands. Average knee angular velocities andaverage contact forces were calculated for the eccentric (knee flexion) and forthe concentric (knee extension) phases of contact.

Figure 1 Jumping exercises: (A) Standing Tive jumps (S5J), standing five hops(SSH), running Hve jumps (R5J), and running flve hops (R5H), (B) hurdle hopping(HH), (C) drop jump with unilateral foot contact (DJ), (D) drop jump with twoapproaching steps (RDJ), and () flop-style high jump (flop).

BIOMECHANICS OF JUMPING 91

The myoelectric activities (EMG) of the three superficial knee extensormuscles (m. vastus lateralis, VL, m. vastus medialis, VM, m. rectus femoris, RFOwere registered by bipolar surface electrodes (Beckman), preamplified, trans-mitted, and received telemetrically (MEDINIC Biotelemetry System IC-600) witha gain of 60 dB. The EMG-, force-, and Elgon-data were stored on a RACAL7 tape recorder for further offline analysis on a HP 1000-F computer. The EMGdata were full-wave rectified and integrated (IEMG) for a precontact phase of80 msec, for the eccentric phase, and for the concentric phase of contact deter-mined by the contact time and minimum knee angle position.

All the IEMG values were related to individual reference IEMGs, whichwere also used to fit the EMG-Ievels of the two measurements days. The refer-ences were obtained from maximum squatting (SJ) and countermovement jumps(CMJ) (see Asmussen & Bonde-Petersen, 1974; Komi & Bosco, 1978) by averag-ing the IEMGs of the eccentric phase of CMJ and concentric phases of SJ andCMJ. Thus the obtained IEMG was a given value of 100 arbitrary units (AU).An example of the data records during an exercise is presented in Figure 2. Eachexercise was performed two to six times by each subject. For further analysisthe repeated measurements and ground contacts were averaged at individual levels.To make a correlative analysis, Pearson's product moment correlation coefficientswere calculated.

ResultsThe basic biomechanical characteristics of the studied jumping exercises arepresented in Figure 3. Contact time (Figure 3a), average contact forces (3b), andaverage knee angular velocities (3c) are presented separately for eccentric andconcentric phases of the takeoff contact. Integrated EMG activities (IEMG) forthe three phases of the jumps are presented in Figure 4, while the intercorrelationcoefficients between different parameters are presented in Figure 5 and Table 1.

The flop-style high jump takeoff was found to have the shortest contact time.75 11 and 102 13 msec for eccentric and concentric phases, respectively, andthe highest average eccentric and concentric contact forces (4575 552 and2051330 N), knee angular velocities (7.12.1. and 6.51.2 rad x sec"') aswell as the highest IEMG activities (1197316 and 736212 AU). The differ-ences in relation to other exercises were profound especially in the eccentric phaseof the takeoff. Among the essential jumping exercises, the ones with a run-up(R5J and R5H) were shown to be more strenuous than the others.

Figure 5 demonstrates the connections between EMG preactivation and thevariables measured in the eccentric phase of contact, as well as between the vari-ables measured in the eccentric and concentric phases. The correlation coefficientshave been calculated using the average values for each jumping exercise. Correla-tion coefficients between preactivation IEMG and the parameters of the eccen-tric phase were statistically highly significant, while the correlation between theparameters of the eccentric and concentric phases were mainly nonsignificant.

The intercorrelations of the parameters in the eccentric and concentric phasesare presented in Table 1. The parameters of the eccentric phase were highly sig-nificantly (p

92 AURA AND VtlTASALO

Verticalforce

Horizontalforce

Pre Ecc Cone

Figure 2 Vertical and horizontal force, knee angle, and EMC of the m. vastusmedialis in running flve hops (R5H). The precontact, eccentric, and concentric phasesare marked below the EMG signal.

DiscussionWidely used jumping exercises were analyzed in the present study to clarify theirbasic biomechanical and neurophysiological characteristics as well as to com-pare the exercises with the high jump takeoff. Generally alt the jumping exer-cises were fast and strenuous compared to average daily locomotive activitiessuch as walking, jogging, and bicycling. However, the exercises didn't exceedthe demands of the flop-style high jump takeoff.

BIOMECHANICS OF JUMPING 93

tcont(mt)

150

100

50

(N)4000

2000

h

Flop RDJ DJ S5J S5H HH R5J R5H

-h

Rop RDJ OJ S5J S5H HH R5J R5H

(rod-Mc*)7

6

5

Flop RDJ DJ S5J S5H HH R5H

Figure 3 Biomechanical characteristics of jumping exercises. Top: eccentric(shaded) and concentric contact times. Middle: average contact forces of the eccen-tric (shaded) and concentric phases. Bottom: average knee angular velocities in eccen-tric (shaded) and concentric phases, MS.E.

94 AURA AND VltTASALO

EMG '(AU)

600

400

200

T

-

-

-

TPRE-ACTIVITY

IEMG(AU)

1200

1000

eoo

600

IEMG(AU)

800

600

400

Fiop RDJ DJ S5J S5H HH R5J R5H

ECCENTRIC ACTIVITY

rh 1

Flop RDJ DJ S5J S5H HH R5J R5H

CONCENTRIC ACTIVITY

Flop RDJ DJ S5J S5H HH R5J R5H

Figure 4 Integrated EMGs (IEMG) of the knee extensor muscles (m. vastuslateralis, m. vastus medialis, and m. rectus Temoris) in precontact, eccentric, andconcentric phases of the jumping exercises, MS.E.

BIOMECHANICS OF JUMPING 95

PRECONTACT ECCENTRIC CONCENTRIC

IEMG

IEMG

IEMG

F:

Figure 5 Correlation coefficients between precontact IEMG and (he parametersof the eccentric phase and between the parameters of the eccentric and the concentricphases. o=;K0.10; *;K0.05, /KO.Ol, ***/K0.001.

In walking, the contact phase of a step cycle can be 550-600 ms and theground reaction forces can be in the range of 1.2 to 2.0 times body weight (BW)(Payne, 1978), while in jogging these values vary between 200-320 ms and2.0 to 3.0 X BW, respectively (Cavanagh & Lafortune, 1980). In jumping exer-cises, foot contact times did vary from 177 to 278 ms, and the average groundreaction forces were 3.5-5.0 X BW (Figure 3). Peak ground reaction forces (cf.Figure 2) were even higher, ranging from 5001 130 N (RDJ) to 82O29O1 N

96 AURA AND VIITASALO

Table 1

tntercorrelation Coefficients Between the Four Variablesin the Eccentric (above) and Concentric (below) Phase of Contact

IEMG

Eccentric IEMGEccentric FEccentric "tj"Eccentric TConcentric IEMGConcentric FConcentr ic"Concentric T

.910***

.963***- .970** *

- .227-.261-.184

.380-.940

.823-.732

-.942*'

- .500

*p

BIOMECHANICS OF JUMPING 97

The correlation coefficients between the parameters of the eccentric andconcentric phase were not significant (Figure 5). However, there are some statisti-cally significant interrelations that are interesting and important when consider-ing the utilization of elastic energy during the concentric force production phaseof the takeoff. The average eccentric and concentric ground reaction forces{defined on the basis of knee flexion and extension) were positively intercorrelated;the eccentric contact time was negatively correlated with the average concentricforce and positively correlated with the concentric contact time. Thus a high eccen-tric force was followed by a high concentric force, and a short eccentric contacttime was followed by a short concentric contact time and a high concentric force.This status in the muscle does allow, on a purely mechanical basis, good possi-bilities for storing and utilizing elastic energy (Cavagna, Saibene. & Margaria,1965). A short contact time and presumably short coupling times (Bosco et al.,1982) between eccentric and concentric contraction further favor the use of theelastic recoil in concentric phases of the jumps when considering the lifetime ofacto-myosin cross-bridges, especially in fast twitch fibers (Lannergren. 1976).

Practice jumping exercises are difficult to perfonn and do require go(xlwarmup and a proper mental frame. The effectiveness of the jumping exercisescan be increased by a run-up in horizontal jumps (Figures 3 and 4) and by higherdropping heights in drop jumps (Bosco, Komi, & Ito. 1981). In maximizingeffectiveness, an athlete should try to make all the takeoffs as fast as possible.

ReferencesAsmussen, E., & Bonde-Petersen, F. (1974). Storage of elastic energy in skeletal muscle

in man. Acta Physiologica Scandinavica, 91, 358-392.Bosco, C , Ito, A., Komi, P.V., Luhtanen. P.. Rahkila. P.. Rusko, H., & Viitasalo. J.T.

(1982). Neuromuscuiar function and mechanical efficiency of human leg extensormuscles during jumping exercises. Acta Physiologica Scandinavica. 114. 543-550.

Bosco, C , Komi, P.V.. & Ito. A. (1981). Prestretch potentiation of human skeletal muscleduring ballistic movement. Acta Physiologica Scandinavica, 111, 135-140.

Cavagna. G.A., Saibene, F.P.. & Margaria, R. (1965). Effect of negative work on theamount of positive work performed by an isolated muscle. Journal of Applied Physi-ology, 20, 157-158.

Cavanagh, P.R., & Lafortune, M. (1980). Ground reaction forces in distance running.Journal of Biomechanics, 13, 397-406.

Dietz, V., Schmidtbleicher. P.. & Noth. J. (1979). Neuronal mechanisms of human loco-motion. Journal of Neurophysiology, 42, 1212-1222.

Hoffer. J.T., & Andreassen, S. (1981). Regulation of soleus muscle stiffness in pre-mammillary cats: Intrinsic and reflex components. Journal of Neurophysiology, 45,267-285.

Komi, P.V. (1985). Ground reaction forces in cross-country skiing. In D.A. Winter,R.W. Norman, R.P. Wells, K.C, Hayes, & A.E. Patia (Eds.), Biomechanics IX B(pp. 185-190). Champaign, IL: Human Kinetics.

Komi, P.V., & Bosco. C. (1978). Utilization of stored elastic energy in leg extensor musclesby men and women. Medicine and Science in Sports, 10, 261-265.

Lannergren, A. (1976). Force-velocity relation of isolated twitch and slow muscle fibres(XV Scandinavian Congress of Physiology and Pharmacology, Arhus 1976). AciaPhysiologica Scandinavica, Suppl., 404, 87.

98 AURA AND VIITASALO

Mellvill-Jones, G., & Watt. D. (1971). Observation on control of stepping and hoppingmovements in man. Joumai of Physiology. (Lond) 219. 709-727.

Payne. A.H. (1978). A comparison of the ground forces in race walking with thosein normal walking and running. In E. Asmussen & K. Jorgensen (Eds,), Bio-meehanics VI A (pp. 293-302). Baltimore: University Park Press,

Viitasalo, J.T,, & Aura. O. (1987). Myoelectrical activity of the leg extensor muscula-ture before ground contact in jumping. In B. johnsson (Ed.). Biomeehanics X-B(pp. 695-700). Champaign. IL: Human Kinetics.

Ackno wiedgmen tsKari Miettunen, Ari Manttari. and Visa Pahtaja are acknowledged for their assistance

in collecting and analyzing the data. This study was supported by the Finnish OlympicCommittee.