Some of it is a refresher from our anatomy book. A couple of high points I found really interesting:

Why do we do those small movements and pulses during class? 

• These movements are isometric (tiny one-inch movements and static holds)
• Gives clients a killer workout because it fires up the muscle and makes it more elastic, but not big enough to tear the muscle (which is why it’s safe to do every day!)
• When clients hold a posture they benefit from continuously engaging the muscle, but also get a mini-recovery with each pulse, enabling clients to stay in the posture longer
• Higher-rep, low-weight exercises target slow-twitch muscles, which help increase endurance
• Benefits: helps maintain muscle strength, improves endurance, targets multiple muscle groups which skyrockets your heart rate (ex. In diamond or power diamond, clients mainly target their quads, but also their calves, hamstrings, glutes, abs [and upper body if using the TRX straps]), brings more body awareness (mind-body connection), quick results, increases flexibility, lengthens/tones muscles and burns fat, low risk of injury

Why do we combine large range and small range movements?

• Small range movements are highly effective, but without large moves clients may miss out on building functional strength and cardiovascular endurance
• Larger, compound movements target fast-twitch muscles, helping with power and speed (think sprinting instead of a marathon)
• Marrying small movements with large range movements and strength training gives clients a well-rounded mix of all three areas (building longer and leaner muscles, pushing their hearts and building strength)

Why do clients’ legs shake during class (especially leg work)?

• Clients spend an extended period in a muscle (quad) contraction, while in an isometric hold to intensify the work 
• Shaking is a sign of muscle fatigue, and clients’ muscles are telling them they REALLY feel it – which means change is happening! It’s a good thing 

If you feel like reading the full articles, you can find them here:

https://www.linkedin.com/pulse/anatomy-barre-class-isotonic-vs-isometric-contraction-julie

http://greatist.com/move/benefits-of-barre-workout