The influence of kineanthropometrical profile in deep-water tethered running

The purpose of this study was to identify the kineanthropometrical parameters that best predict the maximal horizontal propulsive force during deep-water tethered running. 21 young and healthy males with large experience in aquatic exercises (24.3+/-2.7 years old, 191.9+/-82.6 minutes physical activity per week) performed 3 repetitions of maximal deep-water running for 10-s, using a flotation vest (Golfinho, H-906, Coimbra, Portugal). The subjects were connected to a strain gauge (Globus, Ergo Meter, Codigné, Italy) by a cable of steel with reduced elastic properties. The other end of the cable was fasted to a rubber band and this to a swimming starting block. Dynamometrical data was exported and processed with Matlab v. 6.0. It was evaluated the maximal propulsive force (Fx-max) and computed the maximal horizontal propulsive force through a trigonometric correction, as suggested by Taylor et al. (2003). Body mass (SECA, 884, Hamburg, Germany), height (SECA, 242, Hamburg, Germany), body mass index (BMI) and fat mass (BIA 101, RJL Systems, Florence, Italy) were also measured. Surface area (SA) was calculated according to the procedure of Du Bois and Du Bois (Shuter and Aslani, 2000). The forearms (Globus, Ergo Meter, Codigné, Italy) and hands (TSD 121C, Biopac Systems, California, USA) maximal isometric forces were also measured. Intra-cyclic variation of the Fx-max presented a tetra-modal profile. Computing a stepby- step regression equation, for prediction of the Fx-max, the kineanthropometrical variables that entered the model were the forearms maximal isometric force, the BMI, the body mass and the SA (r^2=0.57, p=0.01). The purpose of the study was achieved. Evidences revealed that some kineanthropometrical parameters related to buoyancy force (e.g., fat mass), to drag force (e.g., SA and height), to weight force (e.g., body mass) and to propulsive force (e.g., segmental forces) predicted the Fx-max. This means that, besides physical fitness and technical level, often described in the literature, kineanthropometrical characteristics of the runner also affect significantly his performance during a training session. The main conclusion is that tethered running is significantly associated to kineanthropometrical profile of the runner. So, instructors should pay attention to kineanthropometrical characteristics of runners and how it affects their performance

The influence of kineanthropometrical profile in deep-water tethered running

Aquatic jogging is a variant of head-out aquatic exercises characterised by the walking and/or running of a subject in aquatic environment. The main goal of this aquatic program is to promote an increase of physical fitness, specially the cardiorespiratory component

The effect of short-term endurance and strength training on motor unit conduction velocity

AIM: The aim of this study was to investigate the effect of strength and endurance training on the conduction velocity of vastus medialis obliquus and lateralis single motor units during voluntary sustained knee extensions. METHODS: Seventeen sedentary healthy men (age, mean ± SD, 26.3 ± 3.9 yr) were randomly assigned to one of 2 groups: strength training (ST, n= 8) or endurance training (ET, n= 9). Conventional endurance and strength training was performed three days per week, over a period of 6 weeks. Motor unit conduction velocity (MUCV), maximum voluntary force (MVC) and time-to-task failure at 30% MVC of the knee extensors were measured before and immediately following training. To assess MUCV, multi-channel surface and intramuscular EMG signals were concurrently recorded from the vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles during 60-s isometric knee extensions at 10% and 30% of MVC. RESULTS: After 6 weeks of training, MVC increased in the ST group (16.7 ± 7.4 %; P < 0.05) whereas time to task failure was prolonged in the ET group (33.3 ± 14.2 %; P < 0.05). Both training programs induced an increase in motor unit conduction velocity at both 10% and 30% MVC (P < 0.01). Furthermore after both training programs, the reduction in MUCV over time during the sustained contractions occurred at slower rates compared to baseline (P < 0.01). CONCLUSION: These results indicate that short-term endurance and strength training induce similar alterations of the electrophysiological membrane properties of the muscle fiber and in their changes during sustained contractionsGrant SFRH/BD/31796/2006 from Fundação para a Ciência e a Tecnologia (FCT) of Portuga

Changes in H reflex and V wave following short-term endurance and strength training

This study examined the effects of 3 wk of either endurance or strength training on plasticity of the neural mechanisms involved in the soleus H reflex and V wave. Twenty-five sedentary healthy subjects were randomized into an endurance group (n 13) or strength group (n 12). Evoked V-wave, H-reflex, and M-wave recruitment curves, maximal voluntary contraction (MVC), and time-to-task-failure (isometric contraction at 40% MVC) of the plantar flexors were recorded before and after training. Following strength training, MVC of the plantar flexors increased by 14.4 5.2% in the strength group (P 0.001), whereas time-to-task-failure was prolonged in the endurance group (22.7 17.1%; P 0.05). The V wave-to-maximal M wave (V/Mmax) ratio increased significantly (55.1 28.3%; P 0.001) following strength training, but the maximal H wave-to-maximal M wave (Hmax/Mmax) ratio remained unchanged. Conversely, in the endurance group the V/Mmax ratio was not altered, whereas the Hmax/Mmax ratio increased by 30.8 21.7% (P 0.05). The endurance training group also displayed a reduction in the H-reflex excitability threshold while the H-reflex amplitude on the ascending limb of the recruitment curve increased. Strength training only elicited a significant decrease in H-reflex excitability threshold, while H-reflex amplitudes over the ascending limb remained unchanged. These observations indicate that the H-reflex pathway is strongly involved in the enhanced endurance resistance that occurs following endurance training. On the contrary, the improvements in MVC following strength training are likely attributed to increased descending drive and/or modulation in afferents other than Ia afferents

Adjustments in motor unit properties during fatiguing contractions after training

The objective of the study was to investigate the effect of strength and endurance training on muscle fiber membrane properties and discharge rates of low-threshold motor units of the vasti muscles during fatiguing contractions. Methods: Twenty-five sedentary healthy men (age (mean T SD) = 26.3 T 3.9 yr) were randomly assigned to one of three groups: strength training, endurance training, or a control group. Conventional endurance and strength training was performed 3 dIwkj1, during a period of 6 wk. Motor unit conduction velocity and EMG amplitude of the vastus medialis obliquus and lateralis muscles and biceps femoris were measured during sustained isometric knee extensions at 10% and 30% of the maximum voluntary contraction before and immediately after training. Results: After 6 wk of training, the reduction in motor unit conduction velocity during the sustained contractions at 30% of the maximum voluntary force occurred at slower rates compared with baseline (P G 0.05). However, the rate of decrease was lower after endurance training compared with strength training (P G 0.01). For all groups, motor unit discharge rates declined during the sustained contraction (P G 0.001), and their trend was not altered by training. In addition, the biceps femoris–vasti coactivation ratio declined after the endurance training. Conclusions: Short-term strength and endurance training induces alterations of the electrophysiological membrane properties of the muscle fiber. In particular, endurance training lowers the rate of decline of motor unit conduction velocity during sustained contractions more than strength trainin

Motor unit conduction velocity during sustained contraction after eccentric exercise

BACKGROUND:Eccentric contractions induce muscle fiber damage that is associated with a decreased capacity to generate voluntary force and increased fiber membrane permeability. Changes in fiber membrane permeability results in cell depolarization that is expected to have an effect on the action potential propagation velocity of the muscle fibers. PURPOSE:The aim of the study was to investigate the action potential propagation velocity in individual motor units before and 24 and 48 h after eccentric exercise. METHODS:Multichannel surface and fine-wire intramuscular EMG signals were concurrently recorded from two locations of the right vastus medialis muscle of 10 healthy men during 60-s isometric contractions at 10% and 30% of the maximal force. RESULTS:The maximal force decreased by 26.1 ± 16.1% (P < 0.0001) at 24 h and remained reduced by 23.6 ± 14.5% (P < 0.0001) 48 h after exercise with respect to baseline. With respect to baseline, motor unit conduction velocity decreased (P < 0.05) by (average over 24 and 48 h after exercise) 7.7 ± 2.7% (10% maximal voluntary contraction (MVC), proximal), 7.2 ± 2.8% (10% MVC, distal), 8.6 ± 3.8% (30% MVC, proximal), and 6.2 ± 1.5% (30% MVC, distal). Moreover, motor unit conduction velocity decreased over time during the sustained contractions at faster rates when assessed 24 and 48 h after exercise with respect to baseline for both contraction forces and locations (P < 0.05). CONCLUSIONS:These results indicate that the electrophysiological membrane properties of muscle fibers are altered by exercise-induced muscle fiber damage.Ministry of Science, Research and Technology of Iran (N.H.) and the Danish Technical Research Council (project: Centre for Neuroengineering (CEN), contract no. 26-04-0100) (D.F.)

Can a Halliwick swimming programme develop water competence, static and dynamic balance in disabled participants?

Introduction The Halliwick concept is an aquatic rehabilitation programme aiming to enhance balance and core stability of disabled individuals. Previous studies focused on assessing the participants’ satisfaction on Halliwick programmes or the acquisition of water motor skills (Garcia et al., 2012).Yet, as far as our understanding goes there is not in the literature the assessment of the water independence or the transfer to land-based body balance and posture. Methods Nine individuals (33±12.3 years) diagnosed with cerebral palsy (n=2), mental disability (n=4) and trisomy 21 (n=3) were took part in a Halliwick’s 10-point programme. The programme had a duration of 15 weeks comprising one weekly session with one hour of duration. All sessions were planned and implemented by a trained therapist. In the beginning (W0) and in the end (W15) of the intervention programme it was assessed the water competence, static and dynamic balance. Water competence was assessed by the Water Orientation Test Align 2 (WOTA, in points) that is capped to 81 points (Tiroshi et al., 2008). Static balance was assessed by one-leg stance test (OST, in s) and functional reaching test (FRT, in m) according to standard guidelines. The Time up & go test (TUGT, in s) was selected as a measure of dynamic balance. Results Water competence measured by WOTA 2 showed significant improvements (WOTAW0 = 39±11 vs WOTAW15 = 57±16 points, p <0.01) between the beginning and end of the programme. Static balance also improved. There was a significant change in the OST (OSTW0 = 15.56±12.88 vs OSTW15 = 17.78±12.48 s, p = 0.04) and FRT (FRTW0 = 0.20±0.09 vs FRTW15 = 0.24±0.11 m, p <0.01) performances. Dynamic balance also improved (TUGTW0 = 9.12±2.61 vs TUGTW15 = 7.74±2.52 s, p = 0.01) after the 15th week. Conclusions It can be concluded that 15 weeks of a well-designed Halliwick programme can improve water competence of disabled individuals. Concurrently, it was also noted a positive transfer of the skills acquired in water to on land body balance and posture. Hence, fitness and health practitioners should be aware of the water benefits to improve balance and core stability in disable populations

Cardiovascular effort in different head-out aquatic exercise routines: influence of limbs action and floating equipment.

Introduction Head-out aquatic exercise classes comprise limbs action with or without equipment to diversity and change the intensity of the session. Instructors use arms only, legs only action or full mode of exercise to induce different forms of effort. Although acute physiological response can be dependent from the number of limbs in action or by the inclusion of floating material (Costa et al., 2008), there is a need to stagger those routines for health and conditioning purposes. Methods Ten young and healthy women (22.2±2.6 years, 59.3±12.5 kg of body mass and 1.63±0.08 m of height) were recruited to perform five head-out aquatic exercises: (i) horizontal arms abduction (Ab); (ii) horizontal arms abduction with dumbbells (AbDum); (iii) frontal kick (Fk); (iv) frontal kick with leggings (FkLeg), and; (v) aquatic skiing (Ski). Subjects were randomly assigned to each routine that was performed for three minutes at the cadence of 132 bpm. Cardiovascular response was assessed by heart rate, systolic blood pressure, double product and rating of perceived exertion. Results There were significant and strong variations in all variables according to the routine performed (p 0.64 for all). The heart rate was higher in FkLeg (140.40±25.50 bpm) compared to Ab (110.30±23.75 bpm, p = 0.03) and AbDum (110.00±22.70 bpm, p = 0.04). The systolic blood pressure showed higher values in Fk (120.60±15.20 mmHg) when compared to Ab (104.50±10.80 mmHg, p = 0.05). The double product also showed higher values in Fk (15962.80) and FkLeg (16990.40) when compared to Ab (11608, p < 0.01 and p = 0.01, respectively). Interestingly, the rating of perceived exertion showed lower values in Ski (10.40) than AbDum (13.60, p = 0.01) and FkLeg (15.80, p < 0.01). Conclusions It can be concluded that different head-out aquatic exercise routines, encompassing different limbs or with the aid of floating devices, induce different cardiovascular responses. Actions by the lower limbs are the most intense, while upper limbs elicit a lower exertion. Exercising the four limbs (e.g. aquatic skiing) seems to be less demanding than eliciting only two limbs with the aid of a floating device

Influence of occupational exposure to whole body vibrations on standing balance in earthmoving machine operators

Postural instability due exposure to whole body vibrations (WBV) is very common among earthmoving machine operators. The aim of this study was to analyze the influence of occupational exposure to WBV in the postural stability. The study included two groups of healthy volunteers, which included six experienced earthmoving machine operators (exposed group) and five students recruited from an University (non exposed group). The standing balance was assessed by measuring the centre of pressure (CoP) displacement in a single-task (eyes-open/eyes-closed) during two experimental sessions at the beginning and at the end of the week. In general, the results showed that the standing balance of exposed group was worse than the non exposed group, in the CoP displacement in the medium-lateral direction, which may be due to the vibration input was, predominantly, in the y-axis. However, the results also demonstrated that exposed group developed body compensatory strategies associated to duration of exposure and years performing similar tasks. This evidence was an important contribute to further studies and to plan future ergonomic interventions related to work organization factors as work/rest schemes.info:eu-repo/semantics/publishedVersio

Muscle activation levels during the Push-Up exercise on stable and unstable surfaces.

Introduction: The push-up (PU) is one of the most common strength exercises commonly used in the strength training programs for the upper body. Because Since it is limited to by the body weight, fitness trainers use several alternativesexercise types (e.g. unstable surfaces) have been developed in order to increase the activity activation of the involved muscles. This includes variants with unstable surfaces. This study aims aimed to analyze the changes in the muscle activity pattern induced by either performing PU exercise performed on a stable surface (on the ground) or an unstable surface (on a BOSU®). Methods: Eleven voluntary male subjects (age, mean ± SD: 21.9 ± 4.2 yrs.), familiarized with the push-up’s exercises, has have been recruited for this study. Is was asked to the subjects toSubjects performed firstly 5 repetitions of each push-up exercise (stable vs. unstable surfaces. Electromyographic activity (EMG) from the agonist muscles (clavicular, sternal and chondral portion of pectoral major, triceps brachii and anterior deltoid), antagonist muscles (latissimus dorsi and biceps brachii) and the stabilizer muscles (serratus anterior, superior trapezius, external oblique and erector spinae) has been collected with 11 wireless surface electrodes. and, simultaneously, has been collected kKinematic data. was also recorder to interpret technical execution. Results: The results showed that, from the agonist musclesgroup, only the magnitude of activation of the triceps brachii has been affected by the exercise type (p < 0.001). In the unstable PU the triceps brachii showed higher activation levels than in stable surface (70.13 ± 29.03% and 58.62 ± 25.31%, respectively). Regarding to the antagonist muscles behaviorgroup, the unstable PU exercise induced a higher activity of the brachial biceps and of the latissimus dorsi compared to the stable PU exercise (p <0.05 for both muscles). In additionFinally, for stabilizer muscles, it was observed that , during unstable PU, the upper trapezius activation was, on average, 37.79% higher than in the stable exercise (p <0.01) during unstable PU). Instead, for the serratus anterior, the activation level was, on averaged, significantly higher in the unstable PU exercise than in the stable PU (+ 14.71%, p = 0.01). For the external oblique there were no differences in muscle activity between exercise typess (p = 0.23). However, the activity of the erector spinae was significantly higher in unstable PU exercise (p = 0.01). Conclusion: Thesee results indicate that performing the push up exercise performed on an unstable surface (BOSU®) changes the pattern of activation of antagonist muscles, shoulder stabilizer muscles and agonist muscles, particularly the brachial triceps activation