Hada T, Ohmura H, Mukai K, Eto D, Takahashi T, Hiraga A
Equine Science Division, Hidaka Training and Research Center, Japan Racing Association, 535-13 Nischicha, Urakawa-cho, Uraakawagun, Hokkaido, Japan.
Equine Vet J Suppl. 2006 Aug(36):141-5. doi: 10.1111/j.2042-3306.2006.tb05530.x.
Heart rate (HR) recovery immediately after exercise is controlled by autonomic functions and the time constant (T) calculated from HR recovery is thought to be an index of parasympathetic activity in man.
To investigate whether it is possible to evaluate autonomic function using the time constant in horses.
Five Thoroughbred horses were subjected to a standard exercise test. Following pre-medication with saline, atropine and/or propranolol, the horses ran for 2.5 min at a speed of 8 m/sec at a 10% incline and T was calculated from HR after the exercise. Secondly, 7 Thoroughbred horses were then trained for 11 weeks and T and maximal oxygen uptake (VO2max) measured at intervals of 1 or 2 weeks. In 6 horses, T with atropine pre-medication was also measured before and after the whole training period. Furthermore, the HR variability at rest was evaluated by power spectral analysis at intervals of 3 or 4 weeks.
Time constant was increased by atropine and/or propranolol pre-medication, decreased with the progress of training and inversely correlated with VO2max during training (r = 0.43, P<0.005). Parasympathetic blockade significantly decreased T only after and not before, the training; however, T was lower in post training than in pretraining, irrespective of parasympathetic blockade. On the other hand, parasympathetic activity at rest was attenuated and sympathetic activity became predominant following the training.
Heart rate recovery is affected by sympathetic withdrawal and parasympathetic reactivation in horses and suggests that physical training hastened HR recovery by improving the parasympathetic function after exercise with aerobic capacity. However, the effects of other factors need to be considered because the training effect appeared on T even under parasympathetic blockade. The parasympathetic activity at rest is in contrast to that after exercise, suggesting that T does not reflect parasympathetic activity at rest.
If demonstrated how HR recovery is controlled after exercise, its analysis will be important in the evaluation of physical fitness in horses.
运动后即刻的心率（HR）恢复受自主神经功能控制，由HR恢复计算得出的时间常数（T）被认为是人体副交感神经活动的一个指标。
研究是否可以利用时间常数来评估马的自主神经功能。
对5匹纯种马进行标准运动试验。在给予生理盐水、阿托品和/或普萘洛尔进行预处理后，马匹以8米/秒的速度在10%的坡度上奔跑2.5分钟，并根据运动后的心率计算T值。其次，对7匹纯种马进行为期11周的训练，每隔1或2周测量T值和最大摄氧量（VO2max）。在6匹马中，还在整个训练期前后测量了给予阿托品预处理后的T值。此外，每隔3或4周通过功率谱分析评估静息时的心率变异性。
阿托品和/或普萘洛尔预处理使时间常数增加，随着训练的进行而降低，且在训练期间与VO2max呈负相关（r = 0.43，P<0.005）。副交感神经阻滞仅在训练后而非训练前显著降低T值；然而，无论副交感神经阻滞情况如何，训练后的T值均低于训练前。另一方面，训练后静息时的副交感神经活动减弱，交感神经活动占主导。
马的心率恢复受交感神经撤离和副交感神经再激活的影响，提示体育训练通过提高运动后具有有氧能力时的副交感神经功能加速了心率恢复。然而，由于即使在副交感神经阻滞的情况下训练效果仍出现在T值上，因此需要考虑其他因素的影响。静息时的副交感神经活动与运动后的情况相反，提示T值不能反映静息时的副交感神经活动。
如果能证明运动后心率恢复是如何被控制的，那么其分析对于评估马的体能将具有重要意义。
