Abstract:
The primary purpose of the current investigation was to develop an elevated
muscle fluid level using a human in-vivo model. The secondary purpose was to
determine if an increased muscle fluid content could alter the acute muscle
damage response following a bout of eccentric exercise. Eight healthy,
recreationally active males participated in a cross-over design involving two
randomly assigned trials. A hydration trial (HYD) consisting of a two hour infusion
of a hypotonic (0.45%) saline at a rate of 20mL/minVl .73m"^ and a control trial
(CON), separated by four weeks. Following the infusion (HYD) or rest period
(CON), participants completed a single leg isokinetic eccentric exercise protocol
of the quadriceps, consisting of 10 sets of 10 repetitions with a one minute rest
between each set. Muscle biopsies were collected prior to the exercise,
immediately following and at three hours post exercise. Muscle analysis included
determination of wet-dry ratios and quantification of muscle damage using
toluidine blue staining and light microscopy. Blood samples were collected prior
to, immediately post, three and 24 hours post exercise to determine changes in
creatine kinase (CK), lactate dehydrogenase (LD), interleukin-6 (IL-6) and Creactive
protein (CRP) levels. Results demonstrated an increased muscle fluid
volume in the HYD condition following the infusion when compared to the CON
condition. Isometric peak torque was significantly reduced following the exercise
in both the HYD and CON conditions. There were no significant differences in the
number of areas of muscle damage at any of the time points in either condition,
with no differences between conditions. CK levels were significantly greater
24hour post exercise compared to pre, immediately and three hours post
similarly in both conditions. LD in the HYD condition followed a similar trend as
CK with 24 hour levels higher than pre, immediately post and three hours post
and LD levels were significantly greater 24 hours post compared to pre levels in
the CON condition, with no differences between conditions. A significant main
effect for time was observed for CRP (p<0.05) for time, such that CRP levels
increased consistently at each subsequent time point. However, CRP and IL-6
levels were not different at any of the measured time points when comparing the
two conditions. Although the current investigation was able to successfully
increase muscle fluid volume and an increased CK, LD and CRP were observed,
no muscle damage was observed following the eccentric exercise protocol in the
CON or HYD conditions. Therefore, the hypotonic infusion used in the HYD
condition proved to be a viable method to acutely increase muscle fluid content in
in-vivo human skeletal muscle.
