To perform a descending pyramid select a whole-body exercise for which you have mastered the technique. You're going to be doing a lot of reps so it should be an exercise you are really familiar with and can do well - even when fatigued. Exercises like burpees, sledgehammer swings, box jumps and kettlebell swings are all excellent choices.
Once you have chosen your exercise, decide on how "high" you want to start your pyramid. It pays to be a bit conservative here as what looks easy on paper can add up to a huge number of reps...
5-1 = 15 reps total
10-1 = 55 reps total
12-1 = 78 reps total
15-1 = 120 reps total
20-1 = 210 reps total
25-1 = 325 reps total
Next comes the easy (!!!) part...start your stopwatch and perform the first level of your pyramid e.g. 12 reps, then rest as long as necessary (but no longer - this is against the clock!) and then perform 11 reps, rest again before performing 10 reps and so on until you work you way all the way down to your final rep. Rests are intuitive and are dictated by your current fitness level. As you get into better and better shape you should be able to perform the same workout in ever decreasing times as you rest less and increase your work rate.
Descending pyramid training is a great addition to your workouts for a number of reasons...
Simplicity - all you have to do is count downwards...no sets to count, no rests to time, no weights to change. Just an opportunity to switch off your brain and churn out the reps!
Improved muscular endurance - the high volume of reps that will be performed virtually guarantee a big endurance benefit
Fatigue management - the first few sets of any pyramid are the most dense in terms of reps to be completed but as you fatigue, the rep count comes down. The result is that it's possible to maintain a high work rate for the whole duration of the workout even though you are tiring.
Aerobic & anaerobic conditioning - higher rep counts will challenge the aerobic system where as lower rep counts will challenge the anaerobic system making descending pyramid training very versatile and suitable for a wide range of exercisers and fitness goals.
Descending pyramid training can also be applied to pairs of exercises...
for example pairing 20-1 sledgehammer swings with 20-1 lunges creates a great whole body workout i.e. 20 sledgehammer swings, 20 lunges, 19 swings, 19 lunges, 18 swings, 18 lunges etc. You could even group 3 or more exercises together to make a very demanding descending pyramid circuit. I'm sure you can come up with lots devilish variations to torture yourself or your clients with. If you come up with a good one, why not post it in the comments box so we can all share in the fun!
Another nice variation of the descending pyramid workout is to perform multiple sets. This approach works really well with lower rep pyramids e.g. 5-1 chin ups, rest 1-3 minutes and repeat or 10-1 press ups. This is a variation of ladder training which is discussed in this article and provides a useful way of increasing training volume above normal levels.
Of course, is you are a real sadist, you could do an ascending pyramid, increasing the reps set by set. The rep count would be the same but the training effect would be very different as the hardest sets would come when you were at your most fatigued - a challenge for even the fittest exerciser!
Numerical significance - there is a very popular version of descending pyramid training called the Prisoner Burpee challenge where 20-1 burpees are completed in the shortest time possible. It's a tasty workout which I've done a few times and gotten very close to completing in sub 20 minutes. To "celebrate" my 40th birthday, I decided I'd do the Prisoner Burpee Challenge but rather than the standard 20-1 reps, I performed 40-1 reps making a grand total of 820 Burpees (complete with press up and jump). This took my a shade under 2 hours! My point? Why not celebrate a day of numerical significance by doing your own descending pyramid challenge? If nothing else it will give you serious bragging rights down at the bar afterwards!
Regardless of your goals, descending pyramid training can provide a fun addition to your workout so why not give it a go? But beware...those numbers can look very tame on paper when in reality they add up to a whole load of hurt!