JOURNAL OF SPORTS SCIENCE & MEDICINE
THE REPEATED BOUT EFFECT: DOES EVIDENCE FOR A CROSSOVER EFFECT EXIST?
1Human Performance Laboratory Patrick Gymnasium UVM, Burlington, VT 05401.
2NISMAT, Lenox Hill Hospital New York, New York
Search Google Scholar for Citing Articles
Individuals undergoing an unaccustomed exercise bout incorporating a
high degree of eccentric muscle contractions commonly experience delayed
onset muscle soreness. The damage manifests itself via tenderness, loss
of strength, swelling, elevated muscle enzyme activity and loss of flexibility.
Following an initial "damage bout," a repeated bout results in reduced
symptoms. This protective effect is known as the repeated bout effect
(RBE) and can last up to 24 weeks between bouts. The mechanism for this
RBE is unclear and both central and local mechanisms have been suggested.
In an attempt to test the central hypothesis, 12 subjects (mean age =
22.5± 4yrs, ht = 167±9cm, mass = 71.5±13.5kg) underwent an exercise protocol
whereby one leg was exercised eccentrically and following complete recovery;
the contralateral leg was exercised in the same manner. Subjects were
required to step on and off a 46-cm step for 20 minutes at a cadence of
15 steps/minute. One leg was used to go up the step (concentric) while
the opposite was used to go down (eccentric). Approximately two weeks
later and following complete recovery, the protocol was repeated with
the concentrically exercise leg now performing the eccentric contraction.
Data analyses indicate that muscle damage was induced during both trials
on the eccentrically exercised leg as evidenced by a change in tenderness
(bout 1 P < 0.05: bout 2 P < 0.01), pain scores (bout 1 P < 0.0001; bout
2 P < 0.01), and strength loss (bout 1 P = 0.001; bout 2 P = 0.001) over
the four day follow up period. No tenderness was evident on the concentrically
exercised limbs when compared to baseline (Bout 1: P =0.13, Bout 2: P
= .06). Pain was significantly lower in bout two versus bout one (P< 0.04),
however, we attribute this to a tolerance effect. Neither strength loss
nor tenderness were significantly different between bouts. In the current
study, damage was induced in both bouts in the eccentrically exercised
limbs. This preliminary data does not provide evidence for a central mechanism
in that an initial bout of eccentric exercise using one limb did not provide
protection against damage from a repeated bout with the contralateral
limb two weeks later.