Insertion points & fiber types...

How can you tell what you have? What do you
look for to see if you’ve got long v. short
insertion points for your tendons? In the
same vein, how do you tell if you’ve got predominantly fast-twitch, slow-twitch, or
an even mix of muscle fiber types? That is,
without muscle biopsies, I’m looking for
something I can do in the gym or on my own
here to get a rough idea…

As far as leverage issues (insertion points) you are out of luck unless your interested in multiple incisions at each muscle attachment. You also would need to consider limb length and good understanding of levers, so don’t worry about that. In the gym you can get an idea of fiber type, but it is an ordeal and also has drawbacks. You need to find your 1RM for each exercise. then perform the same exercise with 80% of your 1RM. If you can perform >7-8 reps you lean toward slow twitch. Less than 7-8 more fast twitch. Issues with this is that compound exercises involve multiple muscles some which may be more dominant. Consider the difference in grip width and the influence of triceps in a bench press. What muscle are you testing there? Stabilization is also an issue. Standing exercises require greater core stabilization than seated and machine exercises. When your stabilization becomes ineffective due to fatigue, your set is essentially over even if you haven’t reached max fatigue in the targer muscle.

Your best bet is to take some time to work in multiple rep ranges, 1-3, 4-6, 6-8, and so on and see which is most successful for you in achieving your desired goals.

Even simpler…where you the fastest kid in your class? Can you jump very high? If you’ve been successful in explosive sports you’re most likely fast twitch dominant. If you were the top runner on the cross country team and swam the mile in high school, guess slow twitch. Hope this helps.