Isokinetics and Exercise Science

The aim of the current study was to investigate the effects of different types of strength exercises on the posturographic parameters as a postural stability indicators and selected plasma catecholamine levels as a marker of sympathetic nerve activity in basketball players.

The sample included 13 male, well-trained basketball players, aged 22.3 ± 2.9 y, with a training experience of 8.6 ± 2.3 years. Participants performed three consecutive exercises in successive weekly microcycles. The athletes performed isometric, concentric and eccentric exercises, with random restriction. Postural stability of all subjects was evaluated using a force plate before and after each exercise.

The results revealed a significantly higher effect on the range of sway (RoS) with eyes closed in medial/lateral direction after concentric exercise and RoS with eyes closed in both directions after eccentric and isometric exercises. A significantly higher effect on the standard deviation of sway was observed in the anterior-posterior axis with eyes closed (p= 0.041) and velocity of COP displacement with open eyes(VCOP_OE) (p= 0.007) after the isometric exercises. A modulating effect of the applied exercise types on plasma NA and A levels was not observed, and the results demonstrated that serum 5HT was elevated in response to concentric exercise while diminished in response to both isometric and eccentric exercises.

This study demonstrates that all types of applied exercises impair posture control during single leg stance on a force plate in basketball players but isometric exercise of proximal musculature to a greater extent negatively affects posture control in comparison with distal musculature. Moreover, among the investigated monoamines in well trained athletes, 5HT predominantly took part in modulation of locomotor activity.

The aim of this study was to analyze and compare heart rate (HR), rating of perceived exertion (RPE) response, and peak blood lactate concentration ([lac]-peak) after a resistance exercise session with and without vascular occlusion.

Eight male subjects with previous experience in resistance training (23.38 ± 2.38 years; weight 76.75 ± 8.79 kg; height 1.75 ± 0.07 m) took part in this study. After performing a one repetition maximum(1RM) test, the subjects underwent three random sessions in the leg press exercise: (a) 4 sets of 8 repetitions + 1 set until exhaustion at 80% of 1RM without vascular occlusion (HI); (b) 4 sets of 16 repetitions + 1 set until exhaustion at 40% of 1RM with occlusion (LIO) and (c) 4 sets of 16 repetitions + 1 set with the same number of repetitions as LIO at 40% of 1RM without vascular occlusion (LI), in both legs alternately.

It was observed that both HR and RPE were lower during almost all sessions when compared with HI (p< 0.05). In the LI session, both variables were initially similar in comparison with LIO, differentiating during the session (p< 0.05). The [lac]-peak in LIO was lower than HI, but higher than LI (p< 0.001). The correlations between RPE and HR (r= 0.88), RPE and [lac]-peak (r= 0.75), and HR and [lac]-peak (r= 0.84) were all strong.

Resistance training associated with vascular occlusion causes lower physiological and perceived stress in comparison with conventional high intensity strength training.

: Runners not habituated to the forefoot strike pattern may require specific strengthening of plantar flexor muscles to prevent injuries.

To evaluate the effects of eccentric training for ankle plantar flexors on the kinetic and kinematic parameters of forefoot strike running in individuals not habituated to this type of foot strike.

Twenty-four healthy (12 men, 12 women), 18-25 years of age who were not habituated to forefoot strike running were randomly divided into 2 groups: an experimental group (eccentric training for plantar flexors performed using an isokinetic dynamometer, 3 times a week for 8 weeks) and a control group (no intervention). Kinetic data (ground reaction force) and kinematic data (angles of the ankle, knee and hip in the sagittal plane) were recorded while the subjects performed the forefoot strike running pattern at their preferred speed before and after a period of 8 weeks.

Participants showed a reduction of 20% in the magnitude of the impact as well as an increase of approximately 33% in the plantar flexion angle and an increase of 14% in hip flexion (p < 0.001).

Eccentric training generated measurable changes in the forefoot strike pattern and reduced the impact assessed by ground reaction force.

It has been hypothesized [1] that the amplitude of the mechanomyographic (MMG) signal should track mean power output (MP) during dynamic muscle actions. Bodor's hypothesis has been supported in studies of non-fatigued muscles where MMG amplitude was shown to track velocity-related changes in MP, but not moment production, during concentric and eccentric muscle actions.

The purpose of this study was to further test the hypothesis of Bodor [1] by examining the patterns of MMG amplitude responses during a fatiguing workbout that included repetitions that were characterized by constant moment production, but decreasing MP.

Eleven subjects performed 50 submaximal (65% of peak moment), concentric, isokinetic, forearm flexion repetitions at 60°/s. Polynomial regression analyses were used to examine the composite patterns of responses for moment, MP, and MMG amplitude from the biceps brachii across the fatiguing workbout.

There were linear decreases across the repetitions for MP(r = 0.93) and MMG amplitude (r= 0.70), but no change in moment production.

The current findings extend the hypothesis of Bodor [1] to the process of fatigue and suggested that MMG amplitude may be useful for monitoring decreases in MP during submaximal, fatiguing workbout where moment production is maintained.

Transcranial direct current stimulation (tDCS) seems to modulate cardiac autonomic function and blood pressure (BP) at rest and during exercise. Therefore, it is possible that anodal tDCS could influence post-exercise hypotension.

To investigate whether anodal tDCS applied over the motor cortex would affect cardiac autonomic modulation and BP after resistance exercise.

Twelve apparently healthy young men performed two experimental sessions: anodal tDCS or sham condition followed by resistance exercise. Blood pressure (BP), heart rate (HR), rate-pressure product (RPP), and HR variability (HRV) were obtained before and during post-exercise recovery (at 20 and 60 minutes).

Compared to pre-exercise, systolic BP decreased at 20 and at 60 minutes of post-exercise recovery only in anodal tDCS condition(p = 0.03), with no statistical differences in sham condition (p > 0.05). Diastolic and mean BP reduced after both anodal tDCS and sham conditions with no differences between them (P> 0.05). In comparison with anodal tDCS, there were slower HR recovery (tDCS vs. sham: -2 ± 14 vs. 14 ± 8 bpm) and higher RPP (tDCS vs. sham: -1083 ± 1846 vs. 1672 ± 1275 mmHg × bpm) after exercise following sham condition (P< 0.01). No differences were found in any of the HRV analyzed parameters (P> 0.05).

A single session of primary motor cortex tDCS is capable of decreasing the systolic BP and HR responses, as well as the cardiac work after a resistance exercise session in young normotensive subjects regardless of any changes in cardiac autonomic modulation.

Varying exercise parameters, such as angles of movement, can cause different activation patterns within muscle compartments. Therefore, it is expected that feet positioning variations could influence gastrocnemius activity.

Compare gastrocnemius activation during plantar flexion with feet pointing forwards (FO), inwards (IN) and outwards (OU).

Sixteen physically active men (21 ± 2 years; 1.75 ± 0.06 meters and 74.8 ± 7.2 kg), performed 3 sets of 10 repetitions in each of the following experimental conditions: plantar flexion with feet pointing FO, IN and OU. The root mean square (RMS) of the muscular activation of both gastrocnemius heads was analyzed in each set by electromyography.

For the medial head of the gastrocnemius, the OU condition presented greater RMS values when compared to the IN (z = 3.41; p < 0.001) and FO (z = 2.37; p≤ 0.017) conditions. For the lateral head, however, the IN condition demonstrated greatest RMS when compared with OU (z = 3.20; p = 0.001) and FO (z = 3.25; p = 0.001) conditions.

These results suggest that it is possible to create greater activation sites in the gastrocnemius. Trainers and practitioners could use this to prescribe exercise more efficiently, possibly correcting asymmetries in athletes, especially bodybuilders.

Cryotherapy is a common treatment in sports injury but its effect on proprioception and balance in patients with chronic ankle instability (CAI) is yet unknown.

To investigate the effect of cryotherapy on ankle proprioception and dynamic stance balance in the subjects with CAI.

Thirty-three subjects with CAI participated in this study. A cold pack was applied on anterior-lateral ankle area for 20 minutes. Proprioception and star excursion balance test were performed prior to cryotherapy, immediately after cryotherapy and 30-min after cryotherapy. A two-way ANOVA repeated measure was performed for statistical analysis.

The affected ankle showed a significantly greater proprioceptive error than the unaffected ankle (p < 0.05). Immediately after application of cryotherapy proved significantly detrimental to the reaching distance at either baseline or 30-min after (p < 0.05).

In subjects with CAI cryotherapy may adversely affect dynamic stance balance particularly when the latter follows immediately the application of the former. Coaches and athletes should be aware of this phenomenon.

Flexibility is an important component of physical fitness. However, to date, there is no comparative study between men and women concerning the influence of resistance training (RT) on flexibility.

To analyze the effect of RT on flexibility in young adult men and women.

Twenty-eight men and 30 women underwent progressive RT for 16 weeks, 3 times per week. Anthropometric and flexibility measurements were performed at pre-training, mid-training, and post-training. The flexibility measurements were obtained using a fleximeter.

There was no significant sex by time interaction(P> 0.05) for any outcomes. Both sexes increased flexibility similarly from baseline to mid-training in shoulder extension (10.4-11.1%) and lateral trunk inclination (2.4-3.4%). Shoulder flexion increased at same magnitude in men and women from baseline to post-training (1.3-2.8%). Hip flexion and trunk flexion scores increased from baseline to mid-training(hip flexion = 3.7-3.9%, trunk flexion = 2.7%), however, a decrease was observed from mid- to post-training (hip flexion = -2.4 - -2.6%, trunk flexion = -1.4%) with values returning to baseline with no difference between men and women.

: The results suggest that regardless of sex, RT improves or at least preserves the flexibility of different joint movements in young adult men and women.

Our purpose was to describe the reproducibility and validity of measurements of hip extension strength obtained by hand-held dynamometry from patients participating in inpatient rehabilitation.

Strength measurements were obtained bilaterally from 24 women and 42 men (33-92 years) patients on admission and again the following day. The patients' ability to independently stand from a 45 cm surface and to walk 30 meters was noted.

The relative test-retest reproducibility of the measurements was supported by intraclass correlation coefficients of 0.703 to 0.835. However, absolute reliability as indicated by minimal detectable changes, was not so good. Known-groups validity was evinced by greater hip extension strength among those able to independently complete a sit-to-stand and to walk 30 meters.

Hip extension strength measurements obtained as described herein in an inpatient rehabilitation setting demonstrate good relative reproducibility and known groups validity.