Bigger. Stronger. Faster.
These three words are what every gym rat and athlete strive for. Endles amounts of time are spent both in and out of the gym in the quest for the ultimate gains. Volumes have been written on the exact science between exercise, strength increases, and muscle growth (a.k.a. hypertrophy). Typical programming recommendations have found that strength increases generally correlate to longer rest periods, i.e. 3 to 5 minutes, while hypertrophy is much smaller, around 45 seconds to 1-1/2 minutes.
As most weight lifters know, there's a general consensus that shorter rest periods are better for hypertrophy, while longer rest periods are ideal for improving strength levels. A new study led by a team of reserachers at the University of Birmingham, U.K. investigated the anabolic response to resistance exercise with short vs long rest periods between sets.
The study enlisted 16 male subjects that performed 4 sets of bilateral leg press and leg extension exercise at 75% of their respective 1RM. Sets were performed until momentary muscle failure set in. Rest periods in between each set of exercise was either 1 minute or 5 minutes.
Follow the training session, each male ingested 25g of whey protein. At the conclusion of the test, muscle biopsies were collected from the males time intervals of 0, 4, 24 and 28 hour post-exercise to determine myofibrillar (muscle) protein synthesis (MPS) and intracellular signaling.
Once the biopsies were collected and results analyzed, researchers found that MPS rates increased above resting values over 0–4 hour post-exercise in both 1-minute and 5-minute rest persiods, but was significantly greater following the 5-minute rest period. Additionally, MPS levels remained elevated in the 24-28 hour post-exercise window, but no significant difference was found between the two different rest protocols.
Lastly, serum testosterone levels were greater during the 20–40 minute post-exercise window for the 1-minute rest period vs. the 5-minute rest period.
Researchers ultimately concluded that shorter rest periods between sets yielded inferior muscle protein synthesis during the early post-exercise recovery period compared to the longer rest protocol. When trying to explain this phenomenon, researchers hypothesized the reason was due to "compromised activation of intracellular signalling," meaning that shorter rest does not allow for maximal stimulation of all the muscle fibers to be called into action.
What does this mean?
In the end, both rest protocols yield long-term increases in MPS; however, in the immediate post-exercise window (20-40 minutes post-exercise) MPS levels are elevated to a greater extent from longer rest periods.
Does this mean you have to give up your short rest period "pump" sets at the end of your workout? No, as both long and short rests yield increased MPS. But, this study does suggest that you shouldn't be married to just one rest period if training strictly for hypertrophy. Longer rests may not yield as great a pump during the early portion of your workout, but if you're really after getting bigger, stronger, and faster with your major compound lifts, taking and extra minute or three can go a long way to increasing your gains over the long term.