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High-intensity interval training (HIIT) related neuromuscular adaptations, changes in force production and on-ice performance were investigated in female ice-hockey players during pre-season. 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 (CMJ) heights, plantar flexor maximal voluntary contraction (MVC) and rate of force development (RFD) were measured. In addition, soleus and tibialis anterior muscles activations (electromyography; EMG) 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 co-activation of tibialis anterior muscle during the plantar flexion 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 co-activation. Therefore, HIIT can be recommended in pre-season 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.

Piirainen JM, Linnamo V, Cronin NJ, Avela J. Age-related neuromuscular function and dynamic balance control during slow and fast balance perturbations. J Neurophysiol 110: 2557-2562, 2013. First published September 18, 2013 doi:10.1152/jn.00476.2013.-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/M 20% ) 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 Ͻ 0.05) during anterior perturbations. In Fast, Young showed a trend for faster recovery (37%; P ϭ 0.086) after anterior perturbations. M-wave latency was similar between groups (6.2 Ϯ 0.7 vs. 6.9 Ϯ 1.2 ms), whereas Elderly showed a longer H-reflex latency (33.7 Ϯ 2.3 vs. 36.4 Ϯ 1.7 ms; P Ͻ 0.01). H/M 20% was higher in Young 30 ms after Fast anterior (50%; P Ͻ 0.05) and posterior (51%; P Ͻ 0.05) perturbations. Plantar flexor rapid torque was also higher in Young (26%; P Ͻ 0.05). After combining both groups' data, H/M 20% correlated negatively with Slow peak COP displacement (r ϭ Ϫ0.510, P Ͻ 0.05) and positively with Fast recovery time (r ϭ 0.580, P Ͻ 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.

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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.