Flashcards in Hypertrophy 2 Deck (21)
What is the hormone hypothesis (Kingren et al, 2010)??
From review article, it was believed that testosterone was the major promoter of muscle growth and subsequent strength increases in response to RT in men. Was also beloved that a bout of heavy RT generally included increased secretion of various anabolic and catabolic hormones
Which 4 training variables are thought to be critical for elevating circulating hormones , which is assumed influences muscle hypertrophy?
Load-intensity (kraemer et al, 1990)
Training volume (Gotshalk et al , 1997)
Rest interval (Kraemer et al, 1987)
Exercised muscle mass + order (Kraemer and ratamess, 2005)
What did Ahtianen et al (2003) find???
Found changes in resting testosterone correlate with changes in muscle CSA, but the r=0.76 and n=7, so one data change would massively influence the data
What did Bhasin et al (1996) find??
That supraphysiological doses of testosterone increased fat free mass (kg), BP strength and squatting strength with no exercise, and significantly increased all these measurements with exercise compared to a placebo.
Philp et al (2010) looked at whether growth factors are required for hypertrophy following resistance exercise. What did he find??
Found that mTOR activation precedes insulin/GF pathway following resistance exercise (shown by S6K1 phosphorylation occurring before PKB phosphorylation)
Further, he showed that genetic inhibition of insulin/GH signalling does not affect hypertrophy in mice - as S6k1 phosphorylation still occurred.
Discuss Schroeder and West (2013)??
Shows the circadian changes in endogenous testosterone through the day, and across days.
When looking at the AUC above nadir, exercise was no different to the normal rhythm.
However, exogenous testosterone of 200mg did drastically increase total testosterone.
Discuss the key hormone paper of West et al (2010)??
Split two groups into a low hormone group (trained just biceps) and a high hormone (trained legs and biceps) and found that MPS was identical across conditions - from West et al (2009).
More chronically, greater hormonal elevations (GF, insulin) were seen in the HH group. After 15 weeks of training, MVC, 1RM and 10RM were identical between LH and HH.
Discuss the gender hormone work by West et al (2009)???
Refuted the hypothesis by showing women have test concentrations that are 10-15 x lower than men, and a 45 x difference in ex induced testosteronemia, but still display the same ex induced changes in MPS
Discuss the gender differences work from Abe et al (2000)??
Found on average, skeletal muscle of women typically has 60-80% strength, fibre CSA and whole muscle ACSA of men
- the absolute changes in strength/mass with training are greater for men, but the relative changes are equal in both genders
Discuss West et al (2011)??
Showed that acute hormones (GH, free test, IGF1, cortisol) do not correlate with gains in LBM over 12 weeks of whole body RT in young men.
Mitchell et al (2013) showed a correlation between the AR fold change and mean fibre CSA of r=0.60, following 16 weeks of training. What else did he find??
Significant correlations with IL6 AUC and change in mean CSA, change in type II CSA and change in type I CSA (r~0.5)
West et al (2015) had engineered tendons incubated in the 'rested' or 'exercise' serum for 7 days. What did he find??
8 young males 15 minutes post resistance training (18 sets of heavy load/high volume / high intensity ).
Found GH to be significantly higher in exercise serum compared to rested
- also found collagen and max tendon load to be higher in the exercise vs rest serum.
Henneman et al (1965) and Burd et al (2012) showed what??
That mechanical tension developed with low load lifting is insufficient to recruit / activate type II fibres , unless the lift is performed to volitional fatigue - i.e. There is a stimulators threshold present.
What did Fry et al (2004) find ??
Found that bodybuilders typically display greater type 1 fibre hypertrophy than powerlifters or weight lifters - could this be as a result of higher repetition ranges and training volumes?
What did Dickinson et al (2010) show???
Measured muscle protein FSR in mixed muscle, type I fibres and type II fibres following an acute bout of exercise of leg exercise in 9 men - found type 1 fibre FSR to be significantly higher than type 2.
Discuss Holm et al (2008)??
Had 11 men complete 12 weeks of leg resistance training. 1 leg trained at 16%1RM (36 reps), one leg trained at 70% 1RM for 8 reps.
They found relative CSA change to be higher for the heavy leg compared to the light leg. Both legs did increase CSA pre-post.
Key issue is that RT is not performed to volitional fatigue
Discuss the key paper from Burd et al (2010)??
Had 15 men perform a single bout of resistance exercise.
Study groups : 90%1RM to fatigue for 4 sets, 30%1RM for 4 sets work-matched to 90%1RM, 30%1RM to fatigue for 4 sets.
The volume load was highest in 30FAIL group, as was TUT.
Myo FSR (%change) was higher 4 hours post exercise in 90FAIL and 30FAIL. 24 hours post exercise, 30FAIL was significantly higher than the other groups.
4 hours post ex. P70S6k sig higher than others for 30FAIL and 4E-BP1 sig higher for 30FAIL group
24 hours post ex, 4E-BP1 was sig higher in 90FAIL and 30FAIL group.
Finally, myoFSR 24h post ex was loosely significantly correlated with 4EBP1 phosphorylation (r=0.37)
Discuss Burd et al's other (2010) study looking at 8 recreationally trained males ??
Subjects performed either 1 or 3 sets of a unilateral leg extension until fatigue.
Total volume load was significantly higher for 3 than 1 set.
Myofibrillar FSR was sig higher in 3 set than 1 set, both at 5h fed and 29h fed
P70s6k was sig higher for 3 set than 1 set at 29h fed. No increase from baseline occurred in the 24h fast group.
Finally, a significant correlation (r=0.34) occurred between myofibrillar FSR and p70S6K phosphorylation
Discuss Mitchell et al (2012)??
Had 3 study groups: 30%1RM for 3 sets, 80%1RM for 3 sets, 80% for 1 set.
1 hour after leg training, p70s6k was elevated for both 80% 1RM groups
Quadriceps volume (%change) was considerably higher for both 3 set conditions but this was not significant.
Discuss Mckendry et al (2016)??
Showed that short inter-set rest blunts resistance exercise-induced increases in myofibrillar PS and intracellular signalling in young males.
A greater myo FSR in 5 min rest compared to 1 min rest.
Higher p70s6K 4h post exercise in 5 min rest compared to 1 min rest
Higher rpS6 4h post exercise in 5 min compared to 1 min rest.