Please could you tell me the most effective way of gaining strength without gaining muscle mass and conversely, is there an effective way of losing weight without losing gains in strength?
A common problem with average (non-PTontheNet.com!) personal trainers is that they are mired in the bodybuilding mentality. Many trainers make the mistake of thinking that strength training and bodybuilding are synonymous.
The simplest way to approach this is to work backwards. From a ton of anecdotal evidence and some science, we have an idea of what types of workouts lead to maximum hypertrophy (for more information on this, search the Content Library under keyword "Hypertrophy").
You simply want to do the opposite.
Keep in mind that some of the strongest athletes in the world (pound-for-pound) are Olympic weight lifters. They have to get as strong as possible while remaining in their weight class. In other words, they are masters at increasing strength without maximizing size. Copy their principles.
- Load and Reps: In general, hypertrophy occurs most easily when working with weights that keep you in the eight to 12 rep range. So for your mission, choose a weight that keeps you in the one to six rep range. Zatsiorsky found that Olympic lifters rarely do more than five reps per set. Berger's research showed that 3 x 6 with a 6RM load led to the greatest improvement in strength while Keipen's research indicated that 3 x 5 with a 5RM load was best.
- Rest: Rest periods in the 30 to 90 second range tend to lead to greater hypertrophy. Instead, use rest periods of two to five minutes to help replenish ATP for maximal efforts and force generation and to minimize the build up of lactic acid, which has been linked to hypertrophy.
As for part two of your question, there is no reason to necessarily lose strength if the weight loss is mostly fat.
Siff and Verkoshanky's work showed that doing a 1RM just once a week can significantly increase your strength for up to six weeks. This and other studies indicate that the key to maintaining strength is in the weekly lift of 95 to 100 percent 1RM.
Of course and above all, you must keep your client's goals and the RISK versus benefit in mind at all times (i.e., make sure to progress safely within your client’s physiological and neuromuscular capabilities toward the above loads).