EFFECTS OF SPRINT AND PLYOMETRIC TRAINING ON MORPHOLOGICAL CHARACTERISTICS IN PHYSICALLY ACTIVE MEN

se of this study was to compare the effects of sprint and plyometric training on morphological characteristics of physically active men. One hundred and fifty one physical education students (18-24 years of age) were allocated into one of three groups: the plyometric group (PG; n = 50), the sprint group (SG; n = 50), and the control group (CG; n = 51). Both experimental groups participated in a training programme 3 times a week for 10 weeks. SG performed maximal sprints for distances between 10 and 50 meters, while the training programme in PG consisted of hurdle jumps and drop jumps. Anthropometric measurement was performed in the week before and the week after the experiment. There were no significant differences (P > 0.05) in magnitude of changes in any of the analysed anthropometric variables between the groups. However, a significant decrease (P < 0.0167) in the percentage of body fat (6.1%) was found in SG. We also found a significant decrease (P < 0.0167) in body mass (1%), fat-free mass (0.4%) and body mass index (0.9%) for the SG, but the magnitude of these changes was rather low. We conclude that the short-term explosive-type training programmes in which muscles operate in the fast stretch-shortening cycle conditions (i.e., sprinting, jumping) have a limited potential to induce morphological changes in physically active men. Key words: sprint running, jumping, hypertrophy, body composition EFFEKTE DES SPRINT- UND PLYOMETRISCHEN TRAININGS AUF DIE MORPHOLOGISCHEN CHARAKTERISTIKEN DER REGELMÄßIG SPORTTREIBENDEN STUDENTEN Zusammenfassung: Das Ziel dieser Studie war, die Effekte des Sprinttrainings und des plyometrischen Trainings auf die morphologischen Charakteristiken der regelmäßig sporttreibenden Studenten zu bestimmen. Einhundert einundfünfzig Studenten der Kinesiologie (im Alter 18-24 Jahre) wurden einer der drei Gruppen zugeteilt: der plyometrischen Gruppe (PG; n = 50), der Sprint- (SG; n = 50), und

DIE MORPHOLOGISCHEN CHARAKTERISTIKEN DER REGELMÄßIG SPORTTREIBENDEN STUDENTEN Zusammenfassung: Das Ziel dieser Studie war, die Effekte des Sprinttrainings und des plyometrischen Trainings auf die morphologischen Charakteristiken der regelmäßig sporttreibenden Studenten zu bestimmen. Einhundert einundfünfzig Studenten der Kinesiologie (im Alter 18-24 Jahre) wurden einer der drei Gruppen zugeteilt: der plyometrischen Gruppe (PG; n = 50), der Sprint- (SG; n = 50), und der Kontrollgruppe (CG; n = 51). Die beiden experimentellen Gruppen trainierten 10 Wochen, 3 Mal wöchentlich. Die SG legte die Strecken zwischen 10 und 50m in maximalen Sprintläufen zurück, während das Trainingsprogramm für die PG aus Hoch- und Fallsprüngen bestand. Die anthropometrischen Messungen wurden eine Woche vor und eine nach dem Experiment vorgenommen. Keine signifikante Unterschiede (P > 0,05) im Veränderungsumfang aller analysierten anthropometrischen Variablen wurden zwischen den Gruppen festgestellt. Allerdings wurde eine signifikante Abnahme (P < 0,0167) des prozentualen Körperfettanteils (6,1%) in der SG gefunden. Wir bemerkten auch eine signifikante Abnahme (P < 0,0167) in der Körpermasse (1%), der fettfreien Masse (0,4%) und im Köpermassenindex (0,9%) bei der SG, aber das Ausmaß dieser Veränderungen war ziemlich niedrig. Wir schließen daraus, dass die kurzfristige und explosive Übungen beinhaltenden Trainingsprogramme, bei denen die Muskel in den Umständen des schnellen Dehnungs-Verkürzungs-Zyklus arbeiten (z.B. Sprintläufe, plyometrische Sprünge) einen begrenzten Potential besitzen, um morphologische Veränderungen bei den regelmäßig sporttreibenden Männern beizubringen. Schlüsselwörter: Sprintläufe, Springen, Hypertrophie, Körperzusammensetzung

Marković, G., Jukić, I., Milanović, D. and Metikoš, D.: EFFECTS OF SPRINT AND... Kinesiology 37(2005) 1:32-39 33 Introduction Muscle strength and power are important de- terminants of a successful performance in many individual and team sports. Consequently, during the past decades much attention both from coaches and researchers has been focused on determining the optimal training methods for the development of strength, power and competitive performance (Adams O’Shea, O’Shea, & Climstein, 1992; Lit- tle, Wilson & Ostrowski, 1996; Wilson, Newton, Murphy & Humphries, 1993). Currently, to enhance muscular power and dynamic performance athletes commonly use: 1) heavy resistance training (80- 90% of one repetition maximum; 1RM), and 2) ex- plosive-type training in a form of either resistance training (30-60% of 1RM) or plyometric training (Newton & Kraemer 1994). Previous studies have clearly shown that both heavy-resistance training (Häkkinen, Alen, & Komi, 1985a; Kraemer et al., 2000a) and explo- sive-type resistance training (Häkkinen, Komi, & Alen, 1985b; Wilson, Newton, Murphy, & Hum- phries, 1993) can improve muscle strength, power and athletic performance. However, the exact mech- anisms responsible for the improvement in muscle function and performance differ between these two training methods. In particular, it is well document- ed that heavy-resistance training enhances muscle function by increasing muscle size (i.e., hypertro- phy), and/or by increasing the neural activation of muscle (Häkkinen, Alen, & Komi, 1985a; Jones & Rutherford, 1987; Sale, 1992). In addition, heavy- resistance training can also change body composi- tion by increasing fat-free mass and reducing body fat percentage (Kraemer et al., 2000a). Therefore, changes in muscle function and performance in- duced by heavy-resistance training can partly be the result of adaptive changes in morphology. In contrast, it is generally believed that explosive- type resistance training does not produce substan- tial morphological changes, and that the main adap- tive changes in muscle function and performance as a result of this type of training are due to an in- creased neural activation of muscle (Sale, 1992). However, this is not a universal fi nding and several studies reported also a signifi cant increase in fat- free mass (Häkkinen, Komi, &

substan- tial morphological changes, and that the main adap- tive changes in muscle function and performance as a result of this type of training are due to an in- creased neural activation of muscle (Sale, 1992). However, this is not a universal fi nding and several studies reported also a signifi cant increase in fat- free mass (Häkkinen, Komi, & Alen, 1985b), mus- cle fi bre cross-sectional area (Häkkinen, Komi, & Alen, 1985b) and decrease in percentage of body fat (Häkkinen, Komi, & Alen, 1985b) as a result of explosive-type resistance training, suggesting that explosive-type training of suffi cient intensity and duration can also elicit certain morphological ad- aptation in humans. In addition to both heavy and explosive resist- ance training protocols, plyometric training can also improve muscle function and athletic per- formance (Bobbert, 1990; Gheri, Ricard, Kleiner, & Kirkendall, 1998), and these effects are mainly the result of various neural and mechanical chang- es (Adams, O’Shea, J., O’Shea, K., & Climstein, 1992; Bobbert, 1990; Sale, 1992), although few studies reported an increase in body mass (e.g., Luebbers et al., 2003; Potteiger et al., 1999) and the cross-sectional area of muscle fi bers (Potteiger et al., 1999). Similar to plyometric training, sprint running also represents an explosive-type training method commonly used in athletic training. How- ever, unlike plyometric training, in which the leg extensor muscles operate solely in stretch-shorten- ing cycle (SSC), sprint running involves both con- centric and SSC muscle function (Delecluse, 1997). Moreover, sprint running involves an activation of much greater proportion of muscles compared to plyometric training, thereby increasing the meta- bolic demands of such training. It is also important to stress that several cross-sectional studies showed that sprinters have greater muscle mass (Spenst, Martin, & Drinkwater, 1993) and a larger cross- sectional area of leg extensor muscles (Hakkinen & Keskinen, 1989) compared to endurance-trained athletes or controls a of similar size. It can, therefore, be hypothesized that sprint training might lead to greater morphological changes, compared to plyometric training. Hence, the purpose of this study was to compare the ef- fects of a 10-week sprint and

1993) and a larger cross- sectional area of leg extensor muscles (Hakkinen & Keskinen, 1989) compared to endurance-trained athletes or controls a of similar size. It can, therefore, be hypothesized that sprint training might lead to greater morphological changes, compared to plyometric training. Hence, the purpose of this study was to compare the ef- fects of a 10-week sprint and plyometric training programme on the morphological characteristics in physically active, but untrained men. Methods Subjects One hundred and fi fty one male physical edu- cation students (18-24 years of age) volunteered to participate in this study after having had all of the risks explained to them before the investigation. The study was approved by the Ethics Committee of the Faculty of Kinesiology, University of Za- greb. None of the subjects reported any medical or orthopaedic problems that would compromise his participation and performance in the study. Experimental design The subjects were assigned in alphabetical or- der to one of three groups: the plyometric group (PG; n = 50), the sprint group (SG; n = 50), and the control group (CG; n = 51). The groups did not differ signifi cantly (P > 0.05) in any of the ana- lysed anthropometric measures at the beginning of the experiment. The control group was instruct- ed to maintain their regular daily activities (i.e., academic schedule) and to avoid any additional strenuous physical activity during the study. The subjects in both experimental groups, in addition to their regular academic physical activities, com- pleted 10 weeks of a 3-day a week exercise training programme on alternate days with a pause of one

Marković, G., Jukić, I., Milanović, D. and Metikoš, D.: EFFECTS OF SPRINT AND... Kinesiology 37(2005) 1:32-39 34 week in the middle of the training programme study (see Table 1). The training sessions in both experi- mental groups lasted 60 minutes, and began with a standard 15 minutes warm-up that included run- ning for 5 minutes and was followed by calisthenics, stretching, and 5 submaximal counter movement jumps (PG) or 3 submaximal sprints of 20 meters (SG). The training programme employed by each experimental group is outlined in Table 1. Table 1. Training programme for the plyometric- and sprint-training group. Plyometric group Sprint group Week Exercise × sets × reps Exercise × sets × reps 1 40cm hurdle jumps × 5 × 10 Sprint 10m × 3 × 3 2 40cm hurdle jumps × 7 × 10 Sprint 10m × 4 × 3 3 40cm hurdle jumps × 10 × 10 Sprint 20m × 3 × 3 4 60cm hurdle jumps × 5 × 10 Sprint 20m × 4 × 3 5 60cm hurdle jumps × 7 × 10 Sprint 30m × 3 × 3 6 Rest Rest 7 60cm hurdle jumps × 10 × 10 Sprint 30m × 4 × 3 8 40cm drop jumps × 4 × 10 Sprint 40m × 3 × 3 9 40cm drop jumps × 4 × 10 Sprint 40m × 4 × 3 10 40cm drop jumps × 4 × 10 Sprint 50m × 3 × 3 11 40cm drop jumps × 4 × 10 Sprint 50m × 4 × 3 Note: rest between sets was 2-3 min. The subjects in both experimental groups were instructed to perform exercises in each training ses- sion with maximum effort (i.e. maximal intensity). For the PG, this meant that each jump should be performed to reach maximal height with minimal ground contact time (i.e. so called “bouncing-type” jumps; see Bobbert, 1990). Specifi cally, both hurdle jumps and drop jumps were performed with small knee angular movements, touching the ground with the ball of the feet only (Kovacs et al., 1999), there- by stressing the calf muscles particularly.

meant that each jump should be performed to reach maximal height with minimal ground contact time (i.e. so called “bouncing-type” jumps; see Bobbert, 1990). Specifi cally, both hurdle jumps and drop jumps were performed with small knee angular movements, touching the ground with the ball of the feet only (Kovacs et al., 1999), there- by stressing the calf muscles particularly. Each set of hurdle jumps consisted of ten continuous jumps over hurdles placed in front of the subject with an inter-distance of about 1 meter. Each set of drop jumps consisted of ten maximal rebounds after the drop from the 40 centimetre high box with the pause between each rebound being about 5 seconds (i.e. time needed for the subject to step on to the box again). For the SG, this meant that each sprint run should be performed with maximum accelera- tion and speed. The subjects were also instructed to maintain their normal dietary practices throughout the investigation. The anthropometric measurement was performed in the week before and the week af- ter the 10-week training period. All training ses- sions took place at the same time of day to control the circadian variation in performance. The sub- jects showed 100% compliance with the exercise training programme. Testing procedures All the anthropometric measurements were per- formed by three experienced technicians according to the recommendations of the International Bio- logical Program (Weiner & Lourie, 1969). Body mass and body height were measured by a balance beam scale and a portable stadiometer to the near- est 0.1kg and 0.5cm respectively. Body mass index (BMI) was calculated as follows: BMI = body mass / body height 2 . Skinfold thickness was ob- tained using a Lange skinfold caliper at the calf, chest, thigh, triceps and subscapular re- gions. Three trials were performed and the median value was used in further analysis. The skinfolds recorded at the chest, thigh and subscapular regions were also used for the estimation of body density (Jackson & Pollock, 1978). The body fat percentage was calculated according to the method of Siri (1956). Fat-free mass (FFM) was calculated as

triceps and subscapular re- gions. Three trials were performed and the median value was used in further analysis. The skinfolds recorded at the chest, thigh and subscapular regions were also used for the estimation of body density (Jackson & Pollock, 1978). The body fat percentage was calculated according to the method of Siri (1956). Fat-free mass (FFM) was calculated as the difference between body mass and fat mass. Thigh and calf girths were measured using an anthropometric tape. The calcu- lation of the corrected girths (to estimate the subjects’ thigh and calf muscle girths) used the principal assumptions outlined in Stewart and associates (2002). In brief, tis- sue boundaries were assumed to be circu- lar and concentric. If the skin plus adipose tissue thickness is d, and the thigh and calf girth is G, then the corrected muscle girth (MG) is estimated by MG = G – 2 × π × d (skinfold values are converted to cm for this calculation). If it is further assumed that the skinfold caliper reading S is twice the adipose tissue thickness, then MG = G – π × S. Statistical analysis The data in each group are reported as means ± SD. All the anthropometric variables were normally distributed, as verifi ed by the Kolmogorov-Smirnov Test (P > 0.2). Magnitude of changes in the three groups was compared using a one-way analysis of variance (ANOVA) on the difference (post-test mi- nus pretest) scores. When appropriate, Tukey’s post hoc tests were employed to locate the specifi c sig- nifi cant differences between the groups. The level of statistical signifi cance was set at P < 0.05. Ef- fects of training within each group were assessed using Dunn’s multiple comparison procedure incor- porating the Bonferroni correction to maintain the family-wise Type I error rate at 0.05 (Kirk, 1982). By using the Bonferroni correction, the 0.05 sig- nifi cance level was divided by three (three t-tests), yielding a Type I error rate of 0.0167 for each t-test. The precisions of our estimates of outcome statistics are shown as 95% confi dence limits (which repre- sent the

correction to maintain the family-wise Type I error rate at 0.05 (Kirk, 1982). By using the Bonferroni correction, the 0.05 sig- nifi cance level was divided by three (three t-tests), yielding a Type I error rate of 0.0167 for each t-test. The precisions of our estimates of outcome statistics are shown as 95% confi dence limits (which repre- sent the likely range of the true value in the popu- lation from which the sample was drawn).

Marković, G., Jukić, I., Milanović, D. and Metikoš, D.: EFFECTS OF SPRINT AND... Kinesiology 37(2005) 1:32-39 35 Results Changes in morphological characteristics of the subjects in all groups are depicted in Table 2. There were no signifi cant differences (P > 0.05) in the magnitude of changes in any of the analysed anthropometric variables between the groups. Sprint training resulted in a signifi cant decrease (P < 0.0167) of body mass (1%), BMI (0.9%), FFM (0.4%), and the percentage of body fat (6.1%). No signifi cant differences (P > 0.0167) in the anthro- pometric measures were observed in either PG or CG from pre- to post-training. However, note that the magnitude of changes in the body size meas- ures (i.e., body mass, BMI, and FFM) found in the SG was rather small (0.4-1.0%). Table 2. Anthropometric characteristics (Mean ± SD) for each group at pretest and post-test Plyometric group Pretest Post-test Difference 95% CI Body mass (kg) 77.1 ± 7.5 76.7 ± 7.4 -0.43 -0.85 -0.01 FFM (kg) 70.7 ± 6.2 70.5 ± 6.1 -0.17 -0.56 0.21 Height (cm) 181.6 ± 6.5 181.6 ± 6.5 0.04 -0.20 0.28 BMI (kg/m 2 ) 23.4 ± 1.9 23.2 ± 1.9 -0.15 -0.29 -0.01 Thigh muscle girth (cm) 57.8 ± 3.6 57.3 ± 4.6 -0.50 -1.08 0.08 Calf muscle girth (cm) 37.4 ± 2.2 37.6 ± 2.0 0.21 -0.09 0.51 Body fat (%) 8.2 ± 3.3 7.9 ± 3.5 -0.29 -0.58 0.00 Sprint group Pretest Post-test Difference 95% CI Body mass (kg) 77.3 ± 8.0 76.6 ± 7.8 § -0.70 -1.12 -0.28 FFM (kg) 71.3 ± 6.9 71.0 ± 6.9 § -0.27 -0.65 -0.12 Height (cm) 180.6 ± 7.2 180.6 ± 7.3 0.00 -0.24 0.23 BMI (kg/m 2 ) 23.7 ± 1.8 23.5 ± 1.7 § -0.22 -0.36 -0.08 Thigh muscle girth (cm) 58.0 ± 3.5 58.0 ± 3.2 0.03 -0.55 0.60 Calf muscle girth (cm) 38.0 ± 1.9 38.0 ± 1.9 -0.05 -0.35 0.26 Body fat (%) 7.7 ± 3.0 7.3 ± 2.6 § -0.47 -0.76 -0.18 Control group Pretest Post-test Difference 95% CI Body mass (kg) 74.0 ± 7.9 73.7 ±

± 1.7 § -0.22 -0.36 -0.08 Thigh muscle girth (cm) 58.0 ± 3.5 58.0 ± 3.2 0.03 -0.55 0.60 Calf muscle girth (cm) 38.0 ± 1.9 38.0 ± 1.9 -0.05 -0.35 0.26 Body fat (%) 7.7 ± 3.0 7.3 ± 2.6 § -0.47 -0.76 -0.18 Control group Pretest Post-test Difference 95% CI Body mass (kg) 74.0 ± 7.9 73.7 ± 7.6 -0.31 -0.72 0.11 FFM (kg) 68.8 ±6.3 68.6 ± 6.3 -0.20 -0.59 0.17 Height (cm) 181.2 ± 6.1 181.2 ± 6.2 -0.06 -0.29 0.18 BMI (kg/m 2 ) 22.5 ± 1.9 22.4 ± 1.7 -0.08 -0.21 0.06 Thigh muscle girth (cm) 56.2 ± 3.4 56.1 ± 3.2 -0.05 -0.63 0.52 Calf muscle girth (cm) 36.6 ± 2.3 36.7 ± 2.0 0.04 -0.26 0.34 Body fat (%) 7.9 ± 3.2 7.8 ± 3.2 -0.04 -0.33 0.25 Discussion and conclusions To our knowledge, this is the fi rst study that has compared the effects of sprint and plyometric training on human morphological characteristics. In general, the results of this study show that the 10 weeks of sprint and plyometric training have lim- ited effects on the morphological characteristics of physically active men. In contrast to our hypothe- sis, no signifi cant differences in the magnitude of changes in the anthropometric measures between groups were found. This can be explained by the short duration of the study (i.e. 10 weeks) and by the fact that our subjects belong to the population of young, healthy and physically highly active men. Therefore, a greater overall training volume and/ or a longer duration of the training programme for both sprint and plyometric training are needed to induce greater changes in the morphological sta- tus of physically active men. However, changes in certain morphological characteristics, particularly in the SG, occurred (see Table 2) and deserve to be discussed. An important fi nding of this study is related to the signifi cant decrease in the percentage of body fat observed over the 10 weeks of sprint training. This fi nding is rather surprising considering the fact that fast SSC movements (i.e. sprinting and SSC jumping) are less

in the SG, occurred (see Table 2) and deserve to be discussed. An important fi nding of this study is related to the signifi cant decrease in the percentage of body fat observed over the 10 weeks of sprint training. This fi nding is rather surprising considering the fact that fast SSC movements (i.e. sprinting and SSC jumping) are less metabolically demanding compared to slow movements (Ballor, Becque & Katch, 1987). Moreover, our subjects already had a very low body fat percentage at the beginning of the experiment. Specifi cally, the recorded skinfold values (data not shown) and the derived percentage § Significantly different (P < 0.0167) compared to pretest.

This study compares the effects of sprint and plyometric training on body composition in active men.