Effects of conditioning horses with lactate-guided exercise on muscle glycogen content

Serum muscle-derived enzymes response during show jumping competition in horse

Aim:

The effect of two jumping competitions, performed in two consecutive weekends, on serum creatine phosphokinase (CPK), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH), urea, creatinine (CREA) concentrations were evaluated in 12 healthy jumper horses.

Materials and Methods:

Blood sampling was performed before the 1^st day of competition (T₀), at the end of each show (J₁, J₂), on the day after the competition (T₁); the same sampling plan was followed during the second weekend (J₃, J₄ and T₂).

Results:

One-way repeated measures analysis of variance showed an increase in CPK at J₁ and J₂ respect to T₀ and at J₃ and J₄ respect to all other time points (p<0.05). LDH activity showed an increase at J₂ respect to T₀, at J₃ respect to T₀, J₁, J₂ and at J₄ respect to all other time points (p<0.05). AST values increased at J₁ and J₂ respect to T₀ (p<0.05). A significant increase of CREA was found at J₃ respect to T₀, T₁ and J₁ and at J₄ respect to all other time points (p<0.05). A decrease in serum urea levels was found at J₁ respect to T₀, at J₂ and J₄ respect to T₀ and T₁; at T₂ respect to T₀ (p<0.05). A positive correlation between urea/CPK (p=0.0042, r²=0.030), LDH/CPK (p<0.0001, r²=0.535), CREA/LDH (p<0.0001, r²=0.263), CREA/CPK (p<0.0001, r²=0.496) was observed.

Conclusion:

Our results suggest that 5 days recovery period between the two consecutive competition weekends is insufficient to allow muscle recovery and avoid potential additional stress. The findings obtained in this study improve the knowledge about metabolic changes occurring in athlete horse during the competition to identify muscle alterations following show jumping competitions.

Effects of intensity and duration of exercise on muscular responses to training of thoroughbred racehorses

This study examined the effects of the intensity and duration of exercise on the nature and magnitude of training adaptations in muscle of adolescent (2–3 yr old) racehorses. Six thoroughbreds that had been pretrained for 2 mo performed six consecutive conditioning programs of varying lactate-guided intensities [velocities eliciting blood lactate concentrations of 2.5 mmol/l (v2.5) and 4 mmol/l (v4), respectively] and durations (5, 15, 25 min). Pre- and posttraining gluteus muscle biopsies were analyzed for myosin heavy chain content, fiber-type composition, fiber size, capillarization, and fiber histochemical oxidative and glycolytic capabilities. Although training adaptations were similar in nature, they varied greatly in magnitude among the different training protocols. Overall, the use of v4 as the exercise intensity for 25 min elicited the most consistent training adaptations in muscle, whereas the minimal training stimulus that evoked any significant change was identified with exercises of 15 min at v2.5. Within this range, muscular adaptations showed significant trends to be proportional to the exercise load of specific training programs. Taken together, these data suggest that muscular adaptations to training in horses occur on a continuum that is based on the exercise intensity and duration of training. The practical implications of this study are that exercises for 15 to 25 min/day at velocities between v2.5 and v4 can improve in the short term (3 wk) the muscular stamina in thoroughbreds. However, exercises of 5–15 min at v4 are necessary to enhance muscular features related to strength (hypertrophy).