Using Ice / Cold Water Immersion After Workouts Will Impair Muscle and Strength Gains, as well as Vascular Adaptations

4x fail - if you look at the latest cold-water immersion science.

There are proven acute regenerative benefits of both cold water immersion and cold / ice application after exercise... cool? Not so cool, no. Two recent studies demonstrate: In the long run both will impair your gains.

The studies from Japan (Yamane. 2015) and Norway + Australia (Roberts. 2015) were conducted independently and published almost simultaneously in the International Journal of Sports Medicine and the Journal of Physiology, respectively. Therefore, I'd like to discuss them one after the other, before I finally tie the knots between the studies in a conclusion some of you are not going to like.
"Does Regular Post-exercise Cold Application Attenuate Trained Muscle Adaptation?" that's not only the title, but also the central question in a recent study by Yamane et al. (2015). In the corresponding experiment, 14 male subjects did 5 sets of 8 wrist-flexion exercises at workloads of 70–80% of the single repetition maximum, 3 times a week for 6 weeks. Of the total of 14 male subjects,

• 7 subjects immersed their experimental forearms in cold water (10± 1°C) for 20min after wrist-flexion exercises (cooled group), while
• the other 7 who served as control subjects (noncooled group) refrained from putting their forearms into the 10°C cold water

At the end of the 6-week training period, the wrist-flexor thickness, brachial-artery diameter, maximal muscle strength, and local muscle endurance were measured in upper extremities.

Figure 1: Rel. changes (%) of forearm diameter (muscle size), muscle strength (of the wrist flexors), brachial-artery diameter (vascular adapation) and local muscle endurance (Yamane. 2015).

The results in Figure 1 may come as a nasty surprise to some of you: The wrist-flexor thicknesses of the experimental arms increased after training in both groups, but the extent of each increase was significantly less in the cooled group compared with the non-cooled group.

That this is not a question of post-exercising swelling, only, can be inferred from the fact that the maximal muscle strength and brachial-artery diameter did not increase in the cooled group, either. That's much in contrast to the non-cooled group where both variables as well as the local muscle endurance increased significantly. If we assume that similar effects occur for other muscle parts, it would thus not be a good idea to join Peer Mertesacker in the ice-tub that made him world-famous after the quarter-finals of the soccer world cup, last year.
Now, with just one study investigating only one muscle group, you may well argue that this could be an outlier and eventually it's thus not a problem or even beneficial if you use cold water application or cold water immersion after every workout.

If we add the results Llion A. Roberts et al. present in their accepted article in the The Journal of Physiology, however, it does no longer look like any of the findings were coincidental. After all, Roberts et al. conducted not one but two studies to investigate whether and why "regular cold water immersion influences muscle adaptations to strength" (Roberts. 2015). More specifically, the two experiments the researchers from Norway and Australia conducted were...

• Table 1: Overview of the RT-program in study 1 (Robert. 2015)

  study 1 - 21 physically active men strength trained for 12 weeks (2 d/wk), with either 10 min of CWI or active recovery (ACT) after each training session. The sessions involved mainly the lower body. Training sessions were performed twice a week, separated by 72 h. The loads were set to 8-rep, 10-rep and 12-repetition maximum (RM), and weights corresponding to a proportion of each participant’s body mass.
  
  Strength training was progressive, and included 45° leg press, knee extension, knee flexion, walking lunges and plyometrics exercises. The plyometric component comprised countermovement drop jumps, slow eccentric squat jumps, split lunge jumps and countermovement box jumps. All strength training was supervised and was performed at normal room temperature (23–25°C). 
• study 2 - 9 active men performed a bout of single-leg strength exercises on separate days, followed by CWI or ACT to elucidate the acute effects and potential mechanisms that explain the reduced gains in the chronic training study

The cold water immersion (CWI) itself was performed within 5 min after each training session. The procedure is described as follows: "Participants in the cold water immersion group sat in an inflatable bath (iCool iBody, iCool, Miami, Australia) for 10 min with both legs immersed in water up to the waist. Water was circulated continuously and maintained at 10.1 ± 0.3°C using a circulatory cooling unit (iCool LITE, iCool)" (Roberts. 2015). In contrast, the active recovery group performed 10 min active recovery at a self-selected low intensity on a stationary cycle ergometer (Wattbike, Nottingham, United Kingdom) at a really light mean intensity level of 59.5 ± 9.4 W.

Figure 2: Training-induced changes in type II fiber count and size (left, top), myonucle per fiber (left, bottom), leg press strength (A), knee extension strength (B), isometric torque (C) and RFD impulse (D | Roberts. 2015).

Just as it was the case in the much smaller wrist muscles in the Yamane study, the strength and muscle mass increases in the legs of the subjects in the Roberts study were blunted by the application of cold water (CWI). Practically speaking this means that the isokinetic work (19%), type II muscle fibre cross-sectional area (17%) and the number of myonuclei per fibre (26%) increased in the ACT group (all P<0.05) but not the CWI group.

If you want to know something about the reasons of these statistically significant and practically highly relevant difference are concerned, I suggest you take a closer look at the red box - it may also help you to fully understand the bottom line.
References:

• Roberts, et al. "Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training." The Journal of Physiology (2015): Accepted article.
• Yamane, M., N. Ohnishi, and T. Matsumoto. "Does Regular Post-exercise Cold Application Attenuate Trained Muscle Adaptation?." International journal of sports medicine (2015).