Effects of prior exercise on muscle metabolism during sprint exercise in horses

The effect of warm-up exercise on energy metabolism and muscle glycogenolys is during sprint exercise (Spr) was examined in six fit Standardbred horses exercised at 115% of maximal O-2 consumption ((V) over dot o(2max)) until fatigued, 5 min after each of three protocols: 1) no warm-up (NWU); 2) 10 m in at 50% of (V) over dot o(2max) [low-intensity warm-up (LWU)]; and 3) 7 m in at 50% (V) over dot o(2max) followed by 45-s intervals at 80, 90, and 10 0% (V) over dot o(2max) [high-intensity warm-up (HWU)]. Warm-up increased ( P < 0.0001) muscle temperature (T-m) at the onset of Spr in LWU (38.3 +/- 0 .2 degrees C) and HWU (40.0 +/- 0.3 degrees C) compared with NWU(36.6 +/- 0 .2 degrees C), and the rate of rise in T-m during Spr was greater in NWU th an in LWU and HWU (P < 0.01). Peak (V) over dot o(2) was higher and O-2 def icit lower (P < 0.05) when Spr was preceded by warm-up. Rates of muscle gly cogenolysis were lower (P < 0.05) in LWU, and rates of blood and muscle lac tate accumulation and anaerobic ATP provision during Spr were lower in LWU and HWU compared with NWU. Mean runtime (s) in LWU (173 +/- 10 s) was great er than HWU (142 +/- 11 s) and NWU (124 +/- 4 s) (P < 0.01). Warm-up was as sociated with augmentation of aerobic energy contribution to total energy e xpenditure, decreased glycogenolysis, and longer run time to fatigue during subsequent sprint exercise, with no additional benefit from HWU vs. LWU.