Fotini Arabatzi | Aristotle University of Thessaloniki (original) (raw)

Papers by Fotini Arabatzi

Purpose: The aim of this study was to evaluate physical activity and physical fitness levels in c... more Purpose: The aim of this study was to evaluate physical activity and physical fitness levels in children 7-8 years old with different body mass index (BMI). Methods: Eighty nine children (age 7.6 ± 0.4) participated in this study. BMI was used as obesity indicator and children were categorized in normal-weight and overweight/obese groups. Daily physical activity was assessed by RT3 accelerometer (Stayhealthy Inc, Monrovia, CA) and physical fitness was assessed using the European physical fitness test battery (Eurofit). Results: Analysis of variance (ANOVA) indicated no significant differences in the average daily total counts of physical activity and in scores of four fitness tests between the overweight/obese and normal-weight group (p>0.05). However, boys were significantly more physically active than girls (p<0.05) and the level of physical activity was higher on weekdays than on weekend for both BMI groups (p<0.05). Conclusion: The results indicate that physical activity is not the main contributing factor for childhood overweight at this age. Sufficient levels of daily physical activity were also shown to lead in good physical performance.

The aim of this study was to examine the differences in muscle architecture during isometric test... more The aim of this study was to examine the differences in muscle architecture during isometric tests between children and adults. Eight boys (age= 11.2 ± 0.26 years) and eight men (age= 22.3 ± 2.01 years) performed plantar flexion isometric efforts at angles of-15°, 0°, 15° at 0%, 40%, 60%, 80% of MVC. Analysis of variance tests indicated that adults showed greater fascicle length from rest to 80% of MVC (p < .05), greater pennation angle at 80% and 100% of MVC (p < .05) and greater aponeuroses displacement at levels of effort greater than 60% of MVC (p < .05). These differences observed in MG would appear to favor better utilization of the force-length and the force-velocity relationships, of the muscle in adults compared with children.

AIM: The purpose of this study was to examine the effects of a detraining period after specific p... more AIM: The purpose of this study was to examine the effects of a detraining period after specific plyometric training on vertical jump performance and mechanical properties of aponeurosis of medial gastrocnemius (MG). METHODS: Twenty participants were assigned into two groups and performed plyometric training on incline (IP, N.=10) and plane ground (PP, N.=10), respectively. Vertical jumping (squat jump [SJ], countermovement jump [CMJ], slow and fast drop jumps from 20 and 40 cm [DJ20, DJ40, DJf20, DJf40]) and aponeurosis strain of MG have been re-evaluated four weeks after the end of the training period. The electromyographic (EMG) activity of MG and tibialis anterior (TA) muscles and MG architecture were also recorded after a 4 week of detraining period. RESULTS: After detraining period, jumping height was decreased from 31.20±3.3 cm to 27.5±2 cm and from 31.8±2.9 cm to 29.5±1.9 cm for DJf20 and DJf40, respectively. For the IP group, these changes were accompanied by a significantly lower MG activity during the propulsion phase (from 0.93%±0.09 to 0.77±0.09% and from 0.89±0.09% to 0.60%±0.06 for DJf20 and DJf40, respectively). Similarly, strain was decreased from 22.7% (±0.05) to 16.3% (±0.05) after detraining period. CONCLUSION: These findings suggest that after four weeks of detraining, ankle muscle tendon complex properties withdraw to the pre-training values with lower performance, possible reflecting a different working length of the muscle. .

This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance... more This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance and on peak rate of force development (RFD peak) in preadolescent (10–12 y), adolescents (14–15 y) and adults (20–25 y) males and females. All participants performed a SJ with and without prior conditioning stimulus (PAP and control protocol, respectively), consisting of 3 × 3-second maximal isometric squats. Jump height and RFD-peak of the vertical ground reaction force during SJ were assessed before, and at 20 seconds and at 4 minutes following the conditioning stimulus. The results revealed a different pattern of age-effect on SJ performance within males and females. The RFD peak significantly increased as a factor of age in both males and females (P < .05). Increase in SJ performance after conditioning stimulus occurred only in men (P < .05), with no effects in teen-males, boys, and female groups. There was a significant PAP effect on RFD peak in both adult groups (P < .05) and teen-males, with no effects in children. In conclusion, the PAP effects on SJ performance and RFD peak are age-and sex-dependent; that is PAP appears as a viable method for acutely enhancing SJ performance in men but not in pediatric population.

The Journal of sports medicine and physical fitness, Jan 17, 2014

The purpose of this study was to examine the effects of a detraining period after specific plyome... more The purpose of this study was to examine the effects of a detraining period after specific plyometric training on vertical jump performance and mechanical properties of aponeurosis of Medial Gastrocnemius (MG). Twenty participants were assigned into two groups and performed plyometric training on incline (IP, n=10) and plane ground (PP, n=10), respectively. Vertical jumping (Squat Jump (SJ), Countermovement Jump (CMJ), slow and fast Drop Jumps from 20 and 40 cm (DJ20, DJ40, DJf20, DJf40)) and aponeurosis strain of MG have been re-evaluated four weeks after the end of the training period. The electromyographic (EMG) activity of MG andTibialis Anterior (TA) muscles and MG architecture were also recorded after a 4 week of detraining period. After detraining period, jumping height was decreased from 31.20 ± 3.3 cm to 27.5 ± 2 cm and from 31.8 ± 2.9 cm to 29.5 ± 1.9 cm for DJf20 and DJf40, respectively. For the IP group, these changes were accompanied by a significantly lower MG activity...

The purpose of the present study was a) to study the biomechanical characteristics (kinetic and k... more The purpose of the present study was a) to study the biomechanical characteristics (kinetic and kinemat- ics) which influence the amplitude of maximum vertical ground reaction force (Fzmax), in bilateral landings in children and b) to examine differences in the kinetic and kinematic characteristics of bilateral landing from 20 cm height, among children with different levels of motor coordination. The Movement Assessment Bat- tery for Children (Henderson & Sugden, 1992) was used to assess the coordination level in 35 children (7-9 years old). Nine children (n=9) were reported to have motor coordination problems and formed the motor coordination problems group (MCPG, Body weight: 37.22 ± 6.3 Kg, Body height: 142.22 ± 3.46 cm). Addi- tionally, 9 children with typical coordination comprised the control group (CG, Body weight: 35.83 ± 7.9 Kg, Body height: 141.44 ± 7.67 cm). Groups were videotaped (Panasonic PV-900, 60 Hz) performing bilateral landings, dropping from 20 cm height, on a Ki...

Journal of Strength and Conditioning Research, 2010

Arabatzi, F, Kellis, E, and Saè z-Saez de Villarreal, E. Vertical jump biomechanics after plyomet... more Arabatzi, F, Kellis, E, and Saè z-Saez de Villarreal, E. Vertical jump biomechanics after plyometric, weight lifting, and combined (weight lifting + plyometric) training. J Strength Cond Res 24(9): 2440-2448, 2010-The purpose of this study was to compare the effects of an Olympic weight lifting (OL), a plyometric (PL), and combined weight lifting + plyometric (WP) training program on vertical jump (VJ) biomechanics. Thirty-six men were assigned randomly to 4 groups: PL group (n = 9), OL group (n = 9), WP group (10), and control (C) group (n = 8). The experimental groups trained 3 dÁwk 21 , for 8 weeks. Sagital kinematics, VJ height, power, and electromyographic (EMG) activity from rectus femoris (RF) and medial gastrocnemius (GAS) were collected during squat jumping and countermovement jumping (CMJ) before and after training. The results showed that all experimental groups improved VJ height (p , 0.05). The OL training improved power and muscle activation during the concentric phase of the CMJ while the subjects used a technique with wider hip and knee angles after training (p , 0.05). The PL group subjects did not change their CMJ technique although there was an increase in RF activation and a decrease of GAS activity after training (p , 0.05). The WP group displayed a decline in maximal hip angle and a lower activation during the CMJ after training (p , 0.05). These results indicate that all training programs are adequate for improving VJ performance. However, the mechanisms for these improvements differ between the 3 training protocols. Olympic weight lifting training might be more appropriate to achieve changes in VJ performance and power in the precompetition period of the training season. Emphasis on the PL exercises should be given when the competition period approaches, whereas the combination of OL and PL exercises may be used in the transition phases from precompetition to the competition period.

Journal of Electromyography and Kinesiology, 2003

The purpose of this study was to examine the co-activation of the rectus femoris (RF) and biceps ... more The purpose of this study was to examine the co-activation of the rectus femoris (RF) and biceps femoris (BF) during drop jumping exercises using the co-contraction index (CI). Ten trained male long jumpers performed drop jumps from 20 cm (DJ20), 40 cm (DJ40) and 60 cm (DJ60) on a force platform. Surface electromyographic (EMG) activity of the RF and BF, vertical ground reaction force data and knee joint angular displacement and angular velocities were recorded and normalized as percentage of maximum isometric values. The CI was calculated for the pre-contact, braking and propulsive phases of the jump using four methods: (1) by dividing the double integrated antagonistic activity by the sum of the RF and BF EMG; (2) by finding the amount of overlap between the linear envelopes of the agonist and antagonist muscles and dividing by the number of data points; (3) by calculating the co-contraction at any instant point of time; and (4) by dividing the BF integrated activity by the total registered muscle activity around the knee. The CI ranged from 13.03+/-9.33 to 70.80+/-25.81%, depending on the estimation method used. A two-way analysis of variance (ANOVA) indicated that the CI was not affected by drop jumping height (p>0.05) while it was significantly higher (p<0.05) in the pre-contact phase compared to the braking and propulsion phases. The CI can be useful when examining muscle co-activation using EMG measurements in drop jumps. However, the conclusions on muscle co-activation depend on the equation used to estimate CI and therefore a commonly accepted method is necessary.

Pediatric exercise science, 2014

This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance... more This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance and on peak rate of force development (RFDpeak) in preadolescent (10-12 y), adolescents (14-15 y) and adults (20-25 y) males and females. All participants performed a SJ with and without prior conditioning stimulus (PAP and control protocol, respectively), consisting of 3 × 3-second maximal isometric squats. Jump height and RFDpeak of the vertical ground reaction force during SJ were assessed before, and at 20 seconds and at 4 minutes following the conditioning stimulus. The results revealed a different pattern of age-effect on SJ performance within males and females. The RFDpeak significantly increased as a factor of age in both males and females (P < .05). Increase in SJ performance after conditioning stimulus occurred only in men (P < .05), with no effects in teen-males, boys, and female groups. There was a significant PAP effect on RFDpeak in both adult groups (P < .05) and...

Gait & posture, 2005

Neuroscience Letters, 2003

We examined how young and older adults adapt their posture to static balance tasks of increasing ... more We examined how young and older adults adapt their posture to static balance tasks of increasing difficulty. Participants stood barefoot on a force platform in normal quiet, Romberg-sharpened and one-legged stance. Center of pressure (CoP) variations, electromyographic (EMG) activity of ankle and hip muscles and kinematic data were recorded. Both groups increased postural sway as a result of narrowing the base of support. Greater CoP excursions, EMG activity and joint displacements were noted in old compared to younger adults. Older adults displayed increased hip movement accompanied by higher hip EMG activity, whereas no similar increase was noted in the younger group. It is concluded that older adults rely more on their hip muscles when responding to self induced perturbations introduced by increased task constraints during quiet standing. q

Journal of Strength and Conditioning Research, 2012

Arabatzi, F and Kellis, E. Olympic weightlifting training causes different knee muscle-coactivati... more Arabatzi, F and Kellis, E. Olympic weightlifting training causes different knee muscle-coactivation adaptations compared with traditional weight training. J Strength Cond Res 26(8): 2192-2201, 2012-The purpose of this study was to compare the effects of an Olympic weightlifting (OL) and traditional weight (TW) training program on muscle coactivation around the knee joint during vertical jump tests. Twenty-six men were assigned randomly to 3 groups: the OL (n = 9), the TW (n = 9), and Control (C) groups (n = 8). The experimental groups trained 3 dÁwk 21 for 8 weeks. Electromyographic (EMG) activity from the rectus femoris and biceps femoris, sagittal kinematics, vertical stiffness, maximum height, and power were collected during the squat jump, countermovement jump (CMJ), and drop jump (DJ), before and after training. Knee muscle coactivation index (CI) was calculated for different phases of each jump by dividing the antagonist EMG activity by the agonist. Analysis of variance showed that the CI recorded during the preactivation and eccentric phases of all the jumps increased in both training groups. The OL group showed a higher stiffness and jump height adaptation than the TW group did (p , 0.05). Further, the OL showed a decrease or maintenance of the CI recorded during the propulsion phase of the CMJ and DJs, which is in contrast to the increase in the CI observed after TW training (p , 0.05). The results indicated that the altered muscle activation patterns about the knee, coupled with changes of leg stiffness, differ between the 2 programs. The OL program improves jump performance via a constant CI, whereas the TW training caused an increased CI, probably to enhance joint stability. *Pre = before; post = after; SJ = squat jump; CMJ = countermovement jump; DJ20 = drop jump from 20 cm; DJ40 = drop jump from 40 cm; DJ60 = drop jump from 60 cm.

Gait & Posture, 2005

The present study investigated how young and older individuals organize their posture in response... more The present study investigated how young and older individuals organize their posture in response to self-induced balance perturbations evoked by oscillatory single limb movements. Eleven old (70.1 AE 4.3 years) and nine young (20.1 AE 2.4 years) participants performed repeatedly for 5 s hip flexion/extension movements using full range of motion and maximum velocity. Two-dimensional joint kinematics (sampling rate: 60 Hz), center of pressure (CoP) and EMG activity of tibialis anterior (TA), medial gastrocnemius (MGAS) rectus femoris (RF) and, semitendinosus (ST) in the stance limb were recorded and analysed. Cross-correlation function (CCF) analysis was used to identify the degree of coupling between the swinging limb (SL), center of gravity (CoG) and CoP motions. Old adults significantly limited SL, CoG and CoP range of anterior/posterior (A/P) motion in response to the forceful leg swinging. In the stance limb, significantly lower levels of ankle muscle activity resulted in reduced hip and knee joint excursions and increased ankle instability. By contrast, young performers produced sufficient ankle muscle activity to stabilize the foot to the ground while progressively increasing joint range of motion from the ankle to the hip. Center of pressure and SL movements were strongly correlated in an anti-phase relationship in both age groups. In older adults, however, the relationship between CoG-SL and CoG-CoP movements was neither strong nor synchronous, reflecting a weaker coupling and lack of coordination between component movements. It is concluded that insufficient ankle muscle activity, central integration deficits and increased anxiety to postural threat are important factors implicated for the weaker postural synergies and freezing of degrees of freedom seen in the elderly during performance of single limb oscillations. #

European Journal of Applied Physiology, 2005

The purpose of the present study was to determine the effect of dorsiflexors' ElectroStimulation ... more The purpose of the present study was to determine the effect of dorsiflexors' ElectroStimulation (ES) training, on postural tasks of increasing difficulty in the elderly. Twenty-one elderly adults were randomly assigned into one of two groups: a Training (TG) and a Control Group (CG). The TG (n=10) performed (4 weeks, 4 s/week, 40 min/session) superimposed (electrically evoked and voluntary activation) isometric dorsiflexions (ankle 100°) while seated. Biphasic, rectangular symmetrical pulses (300 ms, 70 Hz, 20-60 mA) were used to provoke maximal muscle activation. Participants performed three static balance tasks (Normal Quiet Stance, Sharpened Romberg, and One-Legged Stance) during which postural sway was quantified using maximum range and standard deviation of Centre of Pressure displacement (Kistler 9281C, 1,000 Hz). Bipolar surface electrodes were used to record the Electromyographic activity (EMG) of Tibialis Anterior, Medial Gastrocnemius, Rectus Femoris and Semi-Tendineous. Two-dimensional kinematic data were collected (60 Hz) and analyzed using the APAS Motion Analysis software. The body was modeled as a five-segment rigid link system. Isometric dorsiflexion moment/angular position relationship was also established using a Cybex dynamometer. ES training resulted in decreased postural sway (P<0.05), greater ankle muscles EMG activity (P<0.001), greater stability of the ankle joint (P<0.05) and significant changes in mean position of all three joints of the lower limb. In addition, dorsiflexion moment significantly (P<0.001) increased as a result of ES training. It is concluded that dorsiflexors' ES training, could reduce postural sway and the use of ankle muscles, more characteristic of young adults, might appear in the elderly as well.

Research in Developmental Disabilities, 2015

The Journal of sports medicine and physical fitness, Jan 17, 2014

Journal of Strength and Conditioning Research, 2010

Journal of Electromyography and Kinesiology, 2003

Pediatric exercise science, 2014

This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance... more This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance and on peak rate of force development (RFDpeak) in preadolescent (10-12 y), adolescents (14-15 y) and adults (20-25 y) males and females. All participants performed a SJ with and without prior conditioning stimulus (PAP and control protocol, respectively), consisting of 3 × 3-second maximal isometric squats. Jump height and RFDpeak of the vertical ground reaction force during SJ were assessed before, and at 20 seconds and at 4 minutes following the conditioning stimulus. The results revealed a different pattern of age-effect on SJ performance within males and females. The RFDpeak significantly increased as a factor of age in both males and females (P < .05). Increase in SJ performance after conditioning stimulus occurred only in men (P < .05), with no effects in teen-males, boys, and female groups. There was a significant PAP effect on RFDpeak in both adult groups (P < .05) and...

Gait & posture, 2005

Neuroscience Letters, 2003

Journal of Strength and Conditioning Research, 2012

Gait & Posture, 2005

European Journal of Applied Physiology, 2005

Research in Developmental Disabilities, 2015