I have no doubt that you have gained significant strength doing yoga. It should be noted that the poses in yoga do involve holding bodyweight, and the increasing complexity and difficulty of the various poses involves progressively more bodyweight resistance per muscle group.
There is no question that intensity can be achieved without weights. I believe what the gentleman was referring to is the science of building significant strength increases over a fit level of baseline strength.
The science on this one is very much settled, courtesy of the not very ethical, but scientifically valid, studies from the Soviet Union in the height of the Cold War.
The science is this:
Lower # of reps at 80 - 90% of a weight you can only lift once builds strength most effieciently.
As you progress up the curve to higher reps at 60%, you are still building strength, but not as efficiently, and you are moving more towards increasing endurance.
Endurance, of course, is most efficiently gained with high # of reps at low percentages. However, this will typically be at the expense of raw strength.
Note: For people who are not at all fit, with atrophied muscles, strength will be gained very easily from almost any use of their muscles, high reps or not.
While the responses to different sorts of training (as in intensity/volume tradeoffs) is considered well-settled, there's still a lot of controversy about the actual physiology, the most efficient programming and so forth.
I guess when someone can do five reps of one armed push ups, five reps of pistol squats and five reps of pull ups (one arm?) then they can say "well, maybe time to drop this scheme and hit the weights"#. But the vast majority of people don't come close to this, so it is completely and utterly absurd for the grandparent to dismiss anything other than barbells for strength training.
#Admittedly it's hard to find a replacement for something like olympic barbells when it comes to exercises such as the deadlift. And of course weights have their benefits with the easier progression, etc etc...
There is no question that intensity can be achieved without weights. I believe what the gentleman was referring to is the science of building significant strength increases over a fit level of baseline strength.
The science on this one is very much settled, courtesy of the not very ethical, but scientifically valid, studies from the Soviet Union in the height of the Cold War.
The science is this:
Lower # of reps at 80 - 90% of a weight you can only lift once builds strength most effieciently.
As you progress up the curve to higher reps at 60%, you are still building strength, but not as efficiently, and you are moving more towards increasing endurance.
Endurance, of course, is most efficiently gained with high # of reps at low percentages. However, this will typically be at the expense of raw strength.
Note: For people who are not at all fit, with atrophied muscles, strength will be gained very easily from almost any use of their muscles, high reps or not.