It is critical to
consider the limitations in this study for example only using elite academy
soccer players could be a limitation as the players might already be accustomed
to training or have naturally high levels of creatine kinase and might be
non-responders to the protocol. It would be beneficial to use untrained
participants as well as elite academy players so you would be able to observe
larger differences between groups. Sample size (N=28) could be considered too
small and may not be representative of bigger populations. Additionally, only
males recruited into the investigation and this could have affected the data in
that there was no variation that could be seen when comparing males and females
and could potentially determine if there are any physiological differences that
could affect the data.
The use of CWI is still challenged as studies
shows that there is no significant difference in CK over the duration of the
experiment and suggests that the intervention could cause athletes to become
more sore as there was a significant difference in pain markers at 24hrs
showing a greater increase in pain in the CWI treatment than control (Sellwood, Brukner, Williams, Nicol, & Hinman,
2007). This could also be down to high
individualisation as some individuals have higher CK levels than others when
placed under the same procedure (Baird, Graham, Baker, & Bickerstaff, 2011).
In reference to peak power output (PPO) there
was statistical significance in both time effect (P<0.001 and time*interaction effect (P<0.001) and they both peaked 24hrs post drop jump. This showed that there was a quicker return to baseline PPO in the CWI intervention group compared to control and shows a quicker return of muscle function and repair. In a recent study it showed there was no significant difference in PPO in either control conditions or CWI which support our data when similar at baseline but does not agree with our data as there was statistical significance at 2hrs and 24hrs post exercise (Nunn & Tyler,2017). Some research also suggests that ice water (5?C) is more beneficial in returning PPO back to baseline than cold water (14?C) (Nunn & Tyler,2017) . The differences in between time*interaction effects in both CK levels and PPO suggested that a single bout of CWI treatment immediately after an intense series of drop jumps is effective in treating indices of EIMD. However other studies have found that single bout CWI has no effect on recovery to help relieve EIMD (Jakeman et al., 2009) as in single bout studies you may not see a significance difference on the first try so need to be repeated in order to see results. This could be down to differences in methodologies for example temperature differences in water suggesting that there needs to be an optimum temperature required. The large peak in CK levels at 24 hours also indicates that the drop jump protocol was intense enough to cause muscle damage. Creatine kinase was an EIMD marker in this investigation and is largely accepted as an EIMD indicator as many other studies have used CK levels to measure EIMD(Glasgow et al., 2014; Jakeman et al., 2009). There was a large significance in both time effect (P< 0.001) and time*interaction effect (P<0.001) in creatine kinase levels which peaked at 24hrs after the drop jump protocol. Another study found that after inducing muscle damage CK activity also peaked at 24hrs (Goodall & Howatson, 2008). Participants receiving treatment by way of CWI demonstrated a quicker return to baseline CK levels than those in the control group. The main findings in relation to muscle soreness across the duration of the experiment showed that there was a notable time effect which began to peak 2hrs after the drop jump protocol and reached its highest at 24hrs showing that participants reported lower perceived muscle soreness in lower limbs in the CWI group. These findings are consistent with those found in (Bailey et al., 2007) as perceived muscle soreness ratings were reduced at 24h post exercise. However, he didn't find that there was a significant effect of CWI on blood CK levels which rejects the findings of this study as there was found to be a significant effect of the use CWI on CK levels. Furthermore, in a recent study it was concluded that there were no positive effects of CWI that were proved to be significant regardless of depth of water (Leeder, van Someren, Bell, Spence, Jewell, Gaze & Howatson, 2015). It also seen that DOMS were highest 24hrs post exercise for both control and seated cold water immersion which does not agree with the evidence from the current experiment, this potentially could be down to differences in method protocol as the duration of immersion were different suggesting an optimum duration time is needed to see similar results (Leeder et al., 2002) FIX. The main findings of this study were that individuals who were in the intervention group that received CWI treatment post drop jump reported lower indices of muscle soreness (P>0.001), and quicker returns to baseline in peak power output (P>0.001)
creatine kinase concentrations (P<0.001). From the dependent variables measured, especially perceived muscle soreness suggested that the drop jump protocol was effective in causing EIMD. This investigation examined the effect of an immediate single bout CWI on the markers of EIMD during a 24- hour recovery period after repeated bouts of a series of drop jumps.