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1.
Brain Sci ; 13(8)2023 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-37626565

RESUMO

Sensorimotor training and strength training can improve balance control. Currently, little is known about how repeated balance perturbation training affects balance performance and its neural mechanisms. This study investigated corticospinal adaptation assessed by transcranial magnetic stimulation (TMS) and Hoffman-reflex (H-reflex) measurements during balance perturbation induced by perturbation training. Fourteen subjects completed three perturbation sessions (PS1, PS2, and PS3). The perturbation system operated at 0.25 m/s, accelerating at 2.5 m/s2 over a 0.3 m displacement in anterior and posterior directions. Subjects were trained by over 200 perturbations in PS2. In PS1 and PS3, TMS and electrical stimulation elicited motor evoked potentials (MEP) and H-reflexes in the right leg soleus muscle, at standing rest and two time points (40 ms and 140 ms) after perturbation. Body sway was assessed using the displacement and velocity of the center of pressure (COP), which showed a decrease in PS3. No significant changes were observed in MEP or H-reflex between sessions. Nevertheless, Δ MEP at 40 ms demonstrated a positive correlation with Δ COP, while Δ H-reflex at 40 ms demonstrated a negative correlation with Δ COP. Balance perturbation training led to less body sway and a potential increase in spinal-level involvement, indicating that movement automaticity may be suggested after perturbation training.

2.
Exp Brain Res ; 241(6): 1599-1610, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37142781

RESUMO

Motoneuron excitability is possible to measure using H-reflex and V-wave responses. However, it is not known how the motor control is organized, how the H-reflex and V-wave responses modulate and how repeatable these are during dynamic balance perturbations. To assess the repeatability, 16 participants (8 men, 8 women) went through two, identical measurement sessions with ~ 48 h intervals, where maximal isometric plantar flexion (IMVC) and dynamic balance perturbations in horizontal, anterior-posterior direction were performed. Soleus muscle (SOL) neural modulation during balance perturbations were measured at 40, 70, 100 and 130 ms after ankle movement by using both H-reflex and V-wave methods. V-wave, which depicts the magnitude of efferent motoneuronal output (Bergmann et al. in JAMA 8:e77705, 2013), was significantly enhanced as early as 70 ms after the ankle movement. Both the ratio of M-wave-normalized V-wave (0.022-0.076, p < 0.001) and H-reflex (0.386-0.523, p < 0.001) increased significantly at the latency of 70 ms compared to the latency of 40 ms and remained at these levels at latter latencies. In addition, M-wave normalized V-wave/H-reflex ratio increased from 0.056 to 0.179 (p < 0.001). The repeatability of V-wave demonstrated moderate-to-substantial repeatability (ICC = 0.774-0.912) whereas the H-reflex was more variable showing fair-to-substantial repeatability (ICC = 0.581-0.855). As a conclusion, V-wave was enhanced already at 70 ms after the perturbation, which may indicate that increased activation of motoneurons occurred due to changes in descending drive. Since this is a short time-period for voluntary activity, some other, potentially subcortical responses might be involved for V-wave increment rather than voluntary drive. Our results addressed the usability and repeatability of V-wave method during dynamic conditions, which can be utilized in future studies.


Assuntos
Reflexo H , Músculo Esquelético , Masculino , Humanos , Feminino , Eletromiografia/métodos , Reflexo H/fisiologia , Músculo Esquelético/fisiologia , Neurônios Motores/fisiologia , Extremidade Inferior , Contração Muscular/fisiologia
3.
Front Physiol ; 13: 957650, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36311220

RESUMO

Following ankle movement, posterior balance perturbation evokes short- (SLR ∼30-50 ms), medium- (MLR ∼50-60 ms), and long-latency responses (LLR ∼70-90 ms) in soleus muscle before voluntary muscle contraction. Transcranial magnetic stimulation (TMS) and Hoffmann-reflex (H-reflex) measurements can provide insight into the contributions of corticospinal and spinal mechanisms to each response. Motor evoked potential (MEP) and H-reflex responses have shown good reliability in some dynamic muscle contraction tasks. However, it is still unclear how reliable these methods are in dynamic balance perturbation and corticospinal modulation during long amplitude balance perturbation tasks. 14 subjects completed two test sessions in this study to evaluate the reliability of MEPs, H-reflex, and corticospinal modulation during balance perturbation. In each session, the balance perturbation system operated at 0.25 m/s, accelerating at 2.5 m/s2 over 0.3 m displacement. MEPs and H-reflexes were elicited in the right leg soleus muscle at four delays after ankle movement (10 ms, 40 ms, 80 ms, and 140 ms), respectively. Test-retest reliability of MEP and H-reflex amplitudes were assessed via intraclass correlation coefficients (ICC) both between- and within-session. Between-session test-retest reliability for MEPs was excellent (ICC = 0.928-0.947), while H-reflex demonstrated moderate-to-good reliability (ICC = 0.626-0.887). Within-session reliability for both MEPs and H-reflex was excellent (ICC = 0.927-0.983). TMS and H-reflex measurements were reliable at different delays after perturbation between- and within-sessions, which indicated that these methods can be used to measure corticospinal excitability during balance perturbation.

4.
Eur J Appl Physiol ; 122(9): 2099-2109, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35729431

RESUMO

PURPOSE: Long-term sports training, such as skill and endurance training, leads to specific neuroplasticity. However, it remains unclear if muscle stretch-induced proprioceptive feedback influences corticospinal facilitation/inhibition differently between skill- and endurance-trained athletes. This study investigated modulation of corticospinal excitability following rapid ankle dorsiflexion between well-trained skill and endurance athletes. METHODS: Ten skill- and ten endurance-trained athletes participated in the study. Corticospinal excitability was tested by single- and paired-pulse transcranial magnetic stimulations (TMS) at three different latencies following passive rapid ankle dorsiflexion. Motor evoked potential (MEP), short-latency intracortical inhibition (SICI), intracortical facilitation (ICF), and long-latency intracortical inhibition (LICI) were recorded by surface electromyography from the soleus muscle. RESULTS: Compared to immediately before ankle dorsiflexion (Onset), TMS induced significantly greater MEPs during the supraspinal reaction period (~ 120 ms after short-latency reflex, SLR) in the skill group only (from 1.7 ± 1.0 to 2.7 ± 1.8%M-max, P = 0.005) despite both conditions being passive. ICF was significantly greater over all latencies in skill than endurance athletes (F (3, 45) = 4.64, P = 0.007), although no between-group differences for stimulations at specific latencies (e.g., at SLR) were observed. CONCLUSION: The skill group showed higher corticospinal excitability during the supraspinal reaction phase, which may indicate a "priming" of corticospinal excitability following rapid ankle dorsiflexion for a supraspinal reaction post-stretch, which appears absent in endurance-trained athletes.


Assuntos
Tornozelo , Treino Aeróbico , Tornozelo/fisiologia , Atletas , Eletromiografia , Potencial Evocado Motor/fisiologia , Humanos , Músculo Esquelético/fisiologia , Tratos Piramidais/fisiologia , Estimulação Magnética Transcraniana
5.
Front Aging Neurosci ; 12: 117, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32508626

RESUMO

Healthy aging is associated with deterioration of the sensorimotor system, which impairs balance and somatosensation. However, the exact age-related changes in the cortical processing of sensorimotor integration are unclear. This study investigated primary sensorimotor cortex (SM1) oscillations in the 15-30 Hz beta band at rest and following (involuntary) rapid stretches to the triceps surae muscles (i.e., proprioceptive stimulation) of young and older adults. A custom-built, magnetoencephalography (MEG)-compatible device was used to deliver rapid (190°·s-1) ankle rotations as subjects sat passively in a magnetically-shielded room while MEG recorded their cortical signals. Eleven young (age 25 ± 3 years) and 12 older (age 70 ± 3 years) adults matched for physical activity level demonstrated clear 15-30 Hz beta band suppression and rebound in response to the stretches. A sub-sample (10 young and nine older) were tested for dynamic balance control on a sliding platform. Older adults had greater cortical beta power pre-stretch (e.g., right leg: 4.0 ± 1.6 fT vs. 5.6 ± 1.7 fT, P = 0.044) and, subsequently, greater normalized movement-related cortical beta suppression post-proprioceptive stimulation (e.g., right leg: -5.8 ± 1.3 vs. -7.6 ± 1.7, P = 0.01) than young adults. Furthermore, poorer balance was associated with stronger cortical beta suppression following proprioceptive stimulation (r = -0.478, P = 0.038, n = 19). These results provide further support that cortical processing of proprioception is hindered in older adults, potentially (adversely) influencing sensorimotor integration. This was demonstrated by the impairment of prompt motor action control, i.e., regaining perturbed balance. Finally, SM1 cortex beta suppression to a proprioceptive stimulus seems to indicate poorer sensorimotor functioning in older adults.

6.
J Strength Cond Res ; 33(2): 479-485, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28277422

RESUMO

Kinnunen, J-V, Piitulainen, H, and Piirainen, JM. Neuromuscular adaptations to short-term high-intensity interval training in female ice-hockey players. J Strength Cond Res 33(2): 479-485, 2019-High-intensity interval training (HIIT)-related neuromuscular adaptations, changes in force production, and on-ice performance were investigated in female ice-hockey players during preseason. Fourteen Finnish championship level ice-hockey players (average age 22 ± 3 years) participated in 2½-week HIIT. Both spinal (H-reflex) and supraspinal (V-wave) neuromuscular responses of the soleus muscle were recorded before and after the training period. Static jump (SJ) and countermovement jump heights, plantarflexor maximum voluntary contraction (MVC), and rate of force development (RFD) were measured. In addition, soleus and tibialis anterior muscle activations (electromyography) were measured during MVC and RFD tests. During on-ice training, skating speed and acceleration tests were performed. Subjects significantly improved their plantarflexion MVC force (11.6 ± 11.2%, p < 0.001), RFD (15.2 ± 15.9%, p < 0.01), and SJ (4.8 ± 7.6%, p ≤ 0.05). Voluntary motor drive to the soleus muscle (V-wave amplitude) increased by 16.0 ± 15.4% (p < 0.01), and coactivation of the tibialis anterior muscle during the plantarflexion RFD test was reduced by -18.9 ± 22.2% (p ≤ 0.05). No change was observed in spinal α-motoneuron excitability (H-reflex) during MVC or in on-ice performance. These results indicate that HIIT can be used to improve athletes' capability to produce maximal and explosive forces, likely through enhanced voluntary activation of their muscles and reduced antagonist coactivation. Therefore, HIIT can be recommended in preseason training to improve neuromuscular performance. However, a longer than 2½-week HIIT period is needed to improve on-ice performance in female ice-hockey players.


Assuntos
Atletas , Desempenho Atlético/fisiologia , Treinamento Intervalado de Alta Intensidade/métodos , Hóquei/fisiologia , Músculo Esquelético/fisiologia , Aceleração , Adaptação Fisiológica/fisiologia , Adolescente , Adulto , Eletromiografia , Feminino , Humanos , Patinação/fisiologia , Adulto Jovem
7.
Mil Med ; 184(3-4): e113-e119, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30053107

RESUMO

INTRODUCTION: Military training loads may induce different physiological responses in garrison and field training and only a little is known about how short-time recovery, lasting a few days, affects neuromuscular fitness and hormonal profile. This study aimed to investigate the effects of garrison and field military service on neuromuscular performance and hormonal profile and to evaluate the effects of a 3-day recovery on those factors. METHODS: Twenty healthy male soldiers (20 ± 1 years) participated in the study, which consisted of 4 days of garrison training [days (D) 1-4] and 7 days of military field training (Days 5-12) followed by a 3-day recovery period (Day 15). Serum hormone concentrations [testosterone (TES), cortisol (COR), sex-hormone binding globulin (SHBG), free thyroxine (T4)] were assessed at D1, D5, D8-12, and D15. Handgrip strength was measured in 10 participants at D1, D5, D8, D12, and D15. Maximal isometric force, electromyography, and rate of force development (RFD) of the knee extensors and arm flexors were also measured at D5, D12, and D15. RESULTS: The maximal force of both the arm flexors and knee extensors was not affected by the garrison or field training, whereas the RFD of the knee extensors was decreased during the field training (D5: 383 ± 130 vs. D12: 321 ± 120 N/s, p < 0.05). In addition, handgrip strength was mostly no affected, although a significant difference was observed between D8 and D12 (531 ± 53 vs. 507 ± 43 N, p < 0.05) during the field training. TES decreased already during the garrison training (D1: 18.2 ± 3.9 vs. D5: 16.2 ± 4.0 nmol/L, p < 0.05) and decreased further during the field training compared to baseline (D8: 10.2 ± 3.6 - D11: 11.4 ± 5.4 nmol/L, p < 0.05) exceeding the lowest concentration in the end of the field training (D12: 7.1 ± 4.1 nmol/L, p < 0.05). Similar changes were observed in free TES (D1: 72.2 ± 31.4 vs. D12: 35.1 ± 21.5 nmol/L, p < 0.001). The TES concentration recovered back to the baseline level and free TES increased after the recovery period compared with the baseline values (D15: 19.9 ± 5.3 nmol/L, D15: 99.7 ± 41.1 nmol/L, respectively). No changes were observed in the COR or SHBG concentrations during the garrison period. COR was decreased in the end of the field training (D12: 388 ± 109 nmol/L) compared with baseline (D1: 536 ± 113 nmol/L) (p < 0.05-0.001) but recovered back to the baseline levels after the recovery period (D15: 495 ± 58 nmol/L), whereas SHBG linearly increased towards the end of the field training (p < 0.05-0.001). CONCLUSIONS: The present findings demonstrate that neuromuscular performance can be relatively well maintained during short-term garrison and field training even when a clear decrease in hormonal profile is evident. In addition, hormonal responses during field training seem to be greater compared to garrison training, however, the recovery of 3-day in free-living conditions seems to be sufficient for hormonal recovery. Therefore, a short-term recovery period lasting few days after the military field training may be required to maintain operational readiness after the field training.


Assuntos
Hormônios/análise , Monitoração Neuromuscular/métodos , Fatores de Tempo , Análise de Variância , Metabolismo Energético/fisiologia , Hormônios/sangue , Humanos , Hidrocortisona/análise , Hidrocortisona/sangue , Masculino , Militares , Força Muscular/fisiologia , Monitoração Neuromuscular/instrumentação , Monitoração Neuromuscular/estatística & dados numéricos , Condicionamento Físico Humano/métodos , Condicionamento Físico Humano/estatística & dados numéricos , Resistência Física/fisiologia , Globulina de Ligação a Hormônio Sexual/análise , Testosterona/análise , Testosterona/sangue , Tiroxina/análise , Tiroxina/sangue , Adulto Jovem
8.
J Electromyogr Kinesiol ; 24(2): 246-52, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24581701

RESUMO

The present study compared neuromuscular adaptations to 12weeks of plyometric (PLY) or pneumatic (PNE) power training and their effects on dynamic balance control. Twenty-two older adults aged 60-70 (PLY n=9, PNE n=11) participated in the study. Measurements were conducted at Pre, 4, 8 and 12weeks. Dynamic balance was assessed as anterior-posterior center of pressure (COP) displacement in response to sudden perturbations. Explosive isometric knee extension and plantar flexion maximal voluntary contractions (MVCs) were performed. Maximal drop jump performance from optimal dropping height was measured in a sledge ergometer. Increases in knee extensor and ankle plantar flexor torque and muscle activity were higher and occurred sooner in PNE, whereas in drop jumping, PLY showed a clearer increase in optimal drop height (24%, p<0.01) after 8weeks of training and soleus muscle activity after 12weeks of training. In spite of these training mode specific adaptations, both groups showed similar improvements in dynamic balance control after 4weeks of training (PLY 38%, p<0.001; PNE 31%, p<0.001) and no change thereafter. These results show that although power and plyometric training may involve different neural adaptation mechanisms, both training modes can produce similar improvements in dynamic balance control in older individuals. As COP displacement was negatively correlated with rapid knee extension torque in both groups (PLY r=-0.775, p<0.05; PNE r=-0.734, p<0.05) after training, the results also highlight the importance of targeting rapid force production when training older adults to improve dynamic balance.


Assuntos
Equilíbrio Postural , Treinamento Resistido , Adaptação Fisiológica , Idoso , Envelhecimento , Eletromiografia , Exercício Físico , Humanos , Contração Isométrica , Joelho , Articulação do Joelho , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/fisiologia , Esportes/fisiologia , Torque
9.
Eur J Sport Sci ; 14(4): 318-26, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-23600926

RESUMO

The purpose of this study was to examine whether split step (small hop before step) would be more beneficial than no-split condition in simulated tennis response situation. In addition, it was studied if movement time of the response is related to separately measured force production capabilities and reflex sensitivity of the players. Nine skilled male tennis players participated in this study. Subjects stood on a force plate and reacted to a light signal and moved to appointed direction as fast as possible. With split step the participants were 13.1% faster (P <0.05) than without split step from the start to the distal end of the so called close range movement continuum (2.70 m). This was mainly explained by 43.6% faster time (P <0.05) from the signal to the onset of force production. Greater vertical forces were observed with split step: 15.7% greater F(z) mean force (P <0.05), 60.0% greater F(z) peak force (P<0.01). In split step both mean (r= - 0.813, P <0.01) and peak (r=-0.765, P <0.05) vertical forces (Fz) correlated negatively with the time from the onset of the force production to the photocell. With split step higher EMGs were observed in muscles responsible for ankle joint movement indicating that different strategies were used. Due to the split step the players were able to start the movement faster which mostly explains the advantages over the no-split step condition. Split step condition may also benefit from stretch shortening type of muscle action.


Assuntos
Movimento/fisiologia , Tempo de Reação/fisiologia , Tênis/fisiologia , Adulto , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos/fisiologia , Eletromiografia , Humanos , Masculino , Músculo Esquelético/fisiologia , Adulto Jovem
10.
J Neurophysiol ; 110(11): 2557-62, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24047908

RESUMO

This study investigated age-related differences in dynamic balance control and its connection to reflexes and explosive isometric plantar flexor torque in 19 males (9 Young aged 20-33 yr, 10 Elderly aged 61-72 yr). Dynamic balance was measured during Slow (15 cm/s) and Fast (25 cm/s) anterior and posterior perturbations. H/M-ratio was measured at 20% of maximal M-wave (H/M20%) 10, 30, and 90 ms after perturbations. Stretch reflexes were measured from tibialis anterior and soleus during anterior and posterior perturbations, respectively. In Slow, Elderly exhibited larger peak center-of-pressure (COP) displacement (15%; P < 0.05) during anterior perturbations. In Fast, Young showed a trend for faster recovery (37%; P = 0.086) after anterior perturbations. M-wave latency was similar between groups (6.2 ± 0.7 vs. 6.9 ± 1.2 ms), whereas Elderly showed a longer H-reflex latency (33.7 ± 2.3 vs. 36.4 ± 1.7 ms; P < 0.01). H/M20% was higher in Young 30 ms after Fast anterior (50%; P < 0.05) and posterior (51%; P < 0.05) perturbations. Plantar flexor rapid torque was also higher in Young (26%; P < 0.05). After combining both groups' data, H/M20% correlated negatively with Slow peak COP displacement (r = -0.510, P < 0.05) and positively with Fast recovery time (r = 0.580, P < 0.05) for anterior perturbations. Age-related differences in balance control seem to be more evident in anterior than posterior perturbations, and rapid sensory feedback is generally important for balance perturbation recovery.


Assuntos
Músculo Esquelético/fisiologia , Equilíbrio Postural , Tempo de Reação , Reflexo , Adulto , Fatores Etários , Idoso , Humanos , Masculino , Contração Muscular , Músculo Esquelético/inervação
11.
J Electromyogr Kinesiol ; 22(6): 852-8, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22739580

RESUMO

The Hoffman reflex (H-reflex), indicating alpha-motoneuron pool activity, has been shown to be task - and in resting conditions - age dependent. How aging affects H-reflex activity during explosive movements is not clear at present. The purpose of this study was to examine the effects of aging on H-reflexes during drop jumps, and its possible role in drop jump performance. Ten young (26.8 ± 2.7 years) and twenty elderly (64.2 ± 2.7 years) subjects participated in the study. Maximal drop jump performance and soleus H-reflex response (H/M jump) 20 ms after ground contact were measured in a sledge ergometer. Maximal H-reflex, maximal M-wave, Hmax/Mmax-ratio and H-reflex excitability curves were measured during standing rest. Although in young the H-reflex response (Hmax/Mmax) was 6.5% higher during relaxed standing and 19.7% higher during drop jumps (H jump/M jump) than in the elderly group, these differences were not statistically significant. In drop jumps, the elderly subjects had lower jumping height (30.4%, p < 0.001), longer braking time (32.4%, p < 0.01), lower push-off force (18.0%, p < 0.05) and longer push-off time (31.0% p < 0.01). H jump/M jump correlated with the average push-off force (r = 0.833, p < 0.05) and with push-off time (r = -0.857, p < 0.01) in young but not in the elderly. Correlations between H-reflex response and jumping parameters in young may indicate different jumping and activation strategies in drop jumps. However, it does not fully explain age related differences in jumping performance, since age related differences in H-reflex activity were non-significant.


Assuntos
Envelhecimento/fisiologia , Reflexo H/fisiologia , Movimento/fisiologia , Músculo Esquelético/fisiologia , Adulto , Eletromiografia , Humanos , Extremidade Inferior/fisiologia , Masculino , Pessoa de Meia-Idade
12.
J Strength Cond Res ; 25(8): 2265-73, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21606858

RESUMO

The purpose of this study was to compare hormonal, neuromuscular, and aerobic performance changes between a constant 2-minute interset recovery time and an interset recovery time based on individual heart rate (HR) responses during a 7-week (3 sessions per week, 3 × 10 repetition maximum [RM]) hypertrophic strength training period. The HR-dependent recovery time was determined with a Polar FT80 HR monitor, whereas the control groups used constant 2-minute periods between sets. From 24 male subjects who were divided in 2 equal groups, 21 completed the study (FT80, n = 12; CONTROL, n = 9). Serum blood samples analyzed for testosterone (TES) and cortisol (COR) were taken before and after the 7-week training period at rest. Concentric knee extension 1RM was measured before, after 4 weeks, and at the end of the training period. Concentric knee extension and knee flexion 10RM, central activation ratio (CAR), and maxVO2 were measured before and after the training. Serum TES concentrations were significantly higher after the training period in FT80 (p < 0.001), whereas no significant changes were observed in the CONTROL. Serum COR and maxVO2 were unchanged in both groups. In FT80 (p < 0.001), the increase in 10RM was higher (p < 0.05) than in CONTROL (p < 0.001). Central activation ratio increased in both groups, with the significant increase observed in FT80 (p < 0.05). The higher TES responses, 10RM, and CAR development in FT80 suggest that an HR-based recovery period system of the FT80 may be more efficient in this type of hypertrophic strength training (3 × 10RM). The protocol in this study may be considered as a metabolic training cycle that coaches and trainers can use within a longer periodized training program.


Assuntos
Exercício Físico , Frequência Cardíaca/fisiologia , Recuperação de Função Fisiológica , Treinamento Resistido , Adulto , Humanos , Hidrocortisona/sangue , Joelho/fisiologia , Masculino , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Testosterona/sangue , Adulto Jovem
13.
J Strength Cond Res ; 22(6): 1916-25, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18978617

RESUMO

The dropout rate in the Finnish military service has increased during the past two decades. At the same time, the physical fitness level of young Finnish males has decreased, possibly leading to overtraining in new conscripts. The purpose of the present study was to examine whether body composition would influence neuromuscular function during the 8-week basic training (BT) period. Eighteen healthy male subjects (19 +/- 1 years) were divided into three different groups according to their body fat %. Group 1 (<10%), group 2 (10-13%) and group 3 (>13%). The soleus H-reflex response was measured in the standing position. In the seated position (knee 160 degrees and hip 110 degrees), the V-wave response was measured during maximal voluntary contraction, and the single twitch response was measured in passive conditions. In body composition (fat-free mass and fat mass) was observed small but not significant changes during 8-week period. H-reflex activity increased in groups 2 (10.9% not significant [ns]) and 3 (2.8% ns) but decreased in group 1 (-34.8%, p < 0.05) during the 8-week period. V-wave values decreased in all groups, and the biggest decrement was observed in group 2 (-34.7%, p < 0.05), whereas in group 1 and group 3 no significance was observed. For each group the single twitch torque (G1 ns, G2 and G3 p < 0.05) increased during the 8-week period. The major finding of the study was that the BT period did not cause overtraining in conscripts. Increased activity of the H-reflex and single twitch torque supports this finding. V-wave activity was decreased in all groups, which may also indicate that the training did not stimulate neural activity. In general, the observed changes in neuromuscular system supports the main finding.


Assuntos
Adiposidade , Militares , Educação Física e Treinamento , Desempenho Psicomotor/fisiologia , Adolescente , Adulto , Análise de Variância , Eletromiografia , Finlândia , Humanos , Contração Isométrica/fisiologia , Modelos Lineares , Masculino , Aptidão Física , Treinamento Resistido
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