LONGITUDINAL RESEARCH OF CALF MUSCLES FUNCTIONAL CHANGES FOR HEALTHY AND WITH ACHILLES TENDON RUPTURE SUBJECTS

Achilles tendon is the strongest tendon in human body, but despite that, it is also one of the common ruptured tendons. When the Achilles tendon rupture (ATR) occurs, strength of calf muscles, proprioception, and postural stability always decrease. It is well known that rehabilitation infuences the greater recovery after Achilles tendon rupture, but despite that the probability of the Achilles tendon re-rupture one year follow up still remains. Therefore, it is very important to understand the ruptured Achilles tendon and calf muscles healing possibilities not only after applied physiotherapy, but also one year follow up. During the present longitudinal research calf muscles strength and proprioception changes of a healthy person and a person with ATR were examined.


Introduction
Achilles tendon is the strongest body tendon (Kaya, Nyland, Toprak, & Turhan, 2012; Mafulli, Oliva, & Ronga, 2013), but despite the strength, it is the most frequently ruptured tendon in the body and comprises about 20 % of all large tendon ruptures (Hashim, Dahabreh, Bin Jemain, & Williams, 2012; Mafulli et al, 2013).Supposedly, one of the reasons of Achilles tendon rupture (ATR) may be inadequate relationship between small tendon crosssectional area and external forces (Kongsgaard, Aagaard, Kjaer, & Magnusson, 2005).ATR causes various acute limitation and chronic adaptation such as calf muscles weakness, decreased functional ability (Bressel, Larsen, McNair, & Cronin, 2003;Maquirriain, 2011), proprioception (Salonikidis, Amiridis, Oxyzoglou, Villared, Zafeiridis, & Kellis, 2009).It is known that pathological musculoskeletal conditions after ATR may be infuenced by the development of adaptive changes in motor strategies, due to mechanical and neural factors (Don, Ranavalo, Cacchio, Serrao, Costable, Iachelli, Camerota, Frascarelli, & Santilli, 2007).Mechanoreceptor activity after ATR is disturbed (Hong & Newell, 2008) Inadequate sensory The sensitivity of the Biodex in torque measurements is ±1.36 Nm.The subjects were secured on an adjustable chair in a slightly reclined position: hip fexed at 75º, knee at 30º angle and strapped at the chest.The foot was held in a place by a heel block and was tightly attached to the plate by two straps.One strap was placed around the foot, 1-2 cm proximal to the metatarsophalangeal joint of the toe, and the second strap was placed around the foot, just below the ankle joint.The position of the subject was adjusted to obtain a 90º angle for the ankle (neutral position 0º).To correct the effect of gravity on the measured joint movements, the passive mass of the foot was measured in the dynamometer at 15 º ankle angles.All subjects were tested without shoes.
Plantar fexion muscles isometric maximal voluntary contraction (MVC) torque was measured in the non-injured (NIL) and injured (IL) leg as well as in the dominant (DL) and non-dominant (NDL) leg.The test started from the NIL and DL leg accordingly in control and experimental groups.Calf muscles MVC torque for each participant was tested at randomized -15º, 0º, and 15 º ankle angles.Participants at each ankle angle performed two ankle fexion and extension repetitions.Rest period between repetitions -30 seconds, and between different ankle angles -60 seconds.
Plantar fexion muscles isometric variability of torque (VT) was measured in the NIL, IL, DL and NDL leg.The test started from the NIL and DL leg plantar fexion, muscles VT.Calf muscles VT were tested at -15º, 0º, 15º ankle angles, which corresponded to ankle angles performed at MVC torque measurement.Isometric torque variability was established during the 20 second isometric contraction at the target torque equal to 40% of isometric MVC torque (see Figure 1).The participants were asked to perform the task as accurately as possible.Participants at each ankle angle performed three ankle fexion and extension repetitions: one with visual feedback (VF) and one without VF.Rest period between repetitions -30 seconds and between different ankle angles -60 seconds.
Physiotherapy took 8 weeks, three times per week; one session lasted 30 minutes.The PT program was directed towards recovery of motion, power and proprioception.All exercises were performed without pain and intensity increased over 8 week PT program period.Each session started with gentle 10 minute warm up.In pronounced ankle joint stiffness, ankle and subtalar joint mobilization was performed, in addition to increase range of motion.For gastrocnemius and soleus muscles -tendon complex stretching exercises were started gently and became more intensive.Eccentric strength training exercises (EE) were applied to increase plantar fexor muscles strength.Resistance exercise were started from and gradually increased to isokinetic close chain.Body balance as well as weight bearing on both legs exercises, were applied for proprioception improvement.
8 week EE for healthy group were performed in order to identify the exercises impact to plantar fexion muscles strength in both groups.All EE were performed three times per week twice a day, one session lasted for 15 minutes.For the frst week EE were performed in close chain and stabile surface, for second 4 weeks EE were performed in close chain and not stabile surface.

LONGITUDINAL RESEARCH OF CALF MUSCLES FUNCTIONAL CHANGES FOR HEALTHY AND WITH ACHILLES TENDON RUPTURE SUBJECTS
Vaida Aleknavičiūtė-Ablonskė, Albertas Skurvydas  Mathematical statistics.The research data were processed employing Microsoft Excel 2010 software for mathematical statistical analysis.The data are reported as group mean values ± standard deviations (SD).Changes between the injury effect (the INL and NL as well as DL and NDL), time impact (before and after 2, 4, 6, 8, 10 month), the task (with or without visual feedback) were evaluated using Student's test (p<0,05 level of signifcance).

LONGITUDINAL RESEARCH OF CALF MUSCLES FUNCTIONAL CHANGES FOR HEALTHY AND WITH ACHILLES TENDON RUPTURE SUBJECTS
Vaida Aleknavičiūtė-Ablonskė, Albertas Skurvydas

Discussion
The main fnding of this study was that (1) eccentric exercises programme decreases calf muscles MVC torque but movement stability becomes greater for healthy person also (2) muscles MVC torque differences between IL and NIL one year follow up for persons with ATR still remain.
Plantar fexion muscles isometric MVC.Calf muscles isometric MVC torque was greater in the DL compared to the NDL as well as in the NIL compared to IL. Plantar fexion muscles isometric MVC torque was greater at -15º (6 month), 0º (6, 10, month), 15º (10 month) ankles angles in the DL compared to the NDL.Some of the authors propose that there is no statistical signifcant difference in calf muscle strength between legs (Damholt & Termansen, 1978; Moraux, Canal, Ollivier, Ledoux, Doppler, Christine Payan, & Hogrel, 2013).The present results are similar to the ones of investigators.The authors of the present research did not establish any statistical signifcant difference between DL and NDL in frst testing time, the difference between DL and NDL was established after 6 and 10 month of participating in investigation.It is well established that 4-6 weeks exercises infuences muscle structural changes (Hotermann et al., 2007).8 week eccentric exercises may infuence muscle hypertrophy (Farthing et al., 2003;Duclay et al., 2009) and greater muscle strength (Farthing et al., 2003).It can be supposed that calf muscle MVC torque between DL and NDL were infuenced by 8 weeks muscle strengthening programme.Plantar fexion muscles isometric MVC torque was greater at -15º (8 month), 0º (4, 12 month), 15º (2, 10, 12 month) ankles angles in the DL compared to the NDL.It is proved that isometric muscle torque differences between NIL and IL remain one year after Achilles tendon rupture surgery (Maquiriain, 2011).Finni (2006) with co-authors examine NIL and IL isometric MVC torque differences of nine persons after Achilles tendon rupture.Results show that after 8 week rehabilitation, plantar fexion muscles isometric MVC torque of the IL increased but still remained lower than of the NIL.Don (2007) with co-authors examines NIL and IL isometric MVC torque differences of 49 persons after Achilles tendon rupture.Results show that MVC torque differences between IL and NIL remain for more that two years.The present results are similar to the ones of the investigators; it can be supposed that it may be the result of inequality muscle spindle (Bressel et al., 2004;Don et al., 2007) which was infuenced by immobilization (Bressel et al., 2004).
After 8 week EE programme calf muscles isometric MVC torque decreases in DL leg at -15º ankle angle.Results data of EE infuence in healthy person muscle strength is controversial.Some authors propose that EE increases muscle strength (Farthing et al., 2003;Duclay et al, 2009;Roig et al, 2011).However intensive EE exercises may induce loss of muscle strength, range of motion, and/or myoglobin concentration in the blood (Chen, Lin, Chen, Lin, & Nosaka, 2011).The present research results are similar to the ones of the investigators; it can be supposed that it may be the result of increased calf muscles tendon stiffness (Duclay et al., 2009).The authors of the present research also established that IL and NIL leg muscles isometric MVC torque increased accordingly at -15º (6 month); 0º (4, 12 and 6 ,8 month); 15º (2, 10, 12 and 10 month) ankle angles.PT program consisted of eccentric muscles strengthening exercises.It is established that six week eccentric muscle strengthening exercises increased concentric and eccentric muscle strength (Kaminski, Wabbersen, & Murphy, 1998).Gastrocnemius and soleus muscles complex can perform 65% of the total 100% MVC force during the plantar fexion movement (Finni et al., 2006).It can be supposed that NIL and IL muscles isometric MVC torque increased due to muscles strengthening exercises.
Muscles isometric variability of torque VT.It is identifed that muscles isometric VT shows movement stability during the task (Kaminski et al, 1998).Plantar fexion muscles isometric VT was greater in DL compared to NDL at 15º 0º ankle angles as well as NIL compared to IL at 15º ankle angle.Separate studies on different subject samples indicate that torque variability depends on muscle torque level, type of contraction and muscle group as well as on variability in discharge rate among active motor units (Skurvydas et al, 2010).It is known that during the tendon injury mechanoreceptors (Kaminski et al, 1998) are disrupted, and this disturbs optimal afferent impulse emanation to CNS (Hong & Newell, 2008).However, it was recently concluded that motor output variability may have benefcial or adverse effects (Stergiou, Harbourne, & Cavanaugh, 2006).An optimal amount of variability of motor performance is benefcial because it reduces the risk of injury (Skurvydas, Masiulis, Gudas, Dargevičiūtė, Parulytė, Trumpickas, & Kalesnikas, 2010).It can be supposed that greater plantar fexion muscles isometric VT in DL may be infuenced by CNS as "protecting mechanism" from risk of injury.And greater muscle VT in NIL compared to IL may be infuenced by intensive healing process in ruptured Achilles tendon.
Movement stability depends on working muscles strength, quality and amount of visual feedback, complexity of task (Smigielski et al, 2008), amount and impulse frequency of recruited motor units (Kaminski et al, 1998).There is non-linear affliation between isometric muscle torque and isometric muscle VT.Muscles isometric VT increased at 20 -60% of muscles isometric MVC torque and decreased at 60 -80% of muscles isometric MVC torque (Christou et al, 2002).Training-induced strength improvement is accompanied by an enhancement of motor-unit synchronization in the agonist muscle as well as reduction of the coactivation of antagonists (Salonikidis et al., 2009).The present results show decreased calf muscles isometric VT (movement stability during the task was improved); it can be supposed that it was infuenced by increased DL and NDL as well as in NIL and IL calf muscles isometric MVC torque.
It was found that visual feedback information is important for the continued maintenance of muscle strength (Hong & Newell, 2008).If the movement was performed with visual feedback and lasted longer than 150 ms, proprioception information allows improving movement stability during the task (Salonikidis et al, 2009).Information about movement

LONGITUDINAL RESEARCH OF CALF MUSCLES FUNCTIONAL CHANGES FOR HEALTHY AND WITH ACHILLES TENDON RUPTURE SUBJECTS
Vaida Aleknavičiūtė-Ablonskė, Albertas Skurvydas possibilities could help to provide a better understanding of how physiotherapy may infuence the properties of scarred Achilles tendon and avoid tendon re-rupture.Aim of the study was to estimate EE effect on the dominant leg, non-dominant leg, non-injured leg and injured leg plantar fexion muscles maximal voluntary contraction (MVC) torque and movement variability (VT) changes one year follow up for healthy and after Achilles tendon rupture persons.Twelve males divided in two groups have been measured.Experimental group consisted of 5 participants, who were 6,5 weeks after Achilles tendon rupture and 10 rehabilitation procedures.Control group consisted of 7 persons who had never had ankle strain, calf muscles rupture and they were not physically active.Control and experimental group performed isometric ankle fexion force accordingly with injured leg, non-injured leg and non-dominant leg and dominant leg.MVC torque and VT were measured at -15°; 0°; 15° angles.The variability of target force was 40% of MVC torque.Both groups performed 8 weeks calf muscles strengthening programme.Calf muscles MVC torque and VT were observed 7 times one time in two month in one year period.
The results of the research.It has been determined that after 8 week muscle strengthening programme calf muscles isometric MVC increased in injured leg, but decreased in dominant leg.Movement stability improved in non-injured leg at 0°; 15° and injured leg at 15° ankle angles.After one year isometric muscle MVC torque increase in dominant leg, non-dominant leg and injured leg at 15° ankle angle.Movement stability improved in non-dominant leg at 15° ankle angle.However, calf muscles isometric MVC as well as isometric muscles VT remain greater in the dominant leg than in the non-dominant leg as well as in non-injured leg than in injured leg.Also after one year MVC torque differences between injured leg and non-injured leg still remain.

Figure 1 .
Figure 1.Calf muscle torque VT and target torque sample