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Abstract
Aim Hypertrophy training is a basic training method to increase muscle size, power and endurance for both athletes and non-athletes. Choosing the most timesaving and beneficial training method is always of concern. Classical hypertrophy training consists of concentric and eccentric contractions of subjected muscle with high-loads (75-85% of 1-Repetition Maximum [RM]) usually in 3 sets. Working with such high loads may cause soreness, pain and loss of function in the following days and producing such effort during training is exhausting for most people. Recently, another type of training, ischaemic or occlusion training is becoming more popular. In this type of training, one restricts blood flow at involved extremity from its proximal to the degree that allows arterial flow but decreases/stops venous return, and then trains with lower loads (20-50% of 1-RM). Prior studies showed similar benefits in terms of hypertrophy measured with arm circumference. However, no study investigated how muscle stiffness values change in both groups after hypertrophy training. Therefore we aimed to measure thickness and stiffness changes of biceps brachii muscles after both classical hypertrophy (CH) and ischaemic hypertrophy (IH) training groups using diagnostic ultrasound device.
Methods 8 healthy volunteers randomised into CH (4) and IH (4) groups. After initial week of familiarisation and baseline measurements conducted in Sports Medicine Department of Istanbul University, participants started 8-weeks training program. Both groups trained with same frequency (3 days a week) but with different intensities. An experienced sports physician recorded thickness measurements using brightness-mode (Image 1) and stiffness measurements using elastography mode (Image 2) of an office type high-equipped ultrasound device before and after the program.
Results No statistically significant difference in muscle thickness was observed before and after training periods in both groups (p = 0.068). Hovewer when analysed together (n = 8), there was a significant increase in muscle thickness (p = 0.012). Muscle stiffness did not change significanlty in either group or in total (p = 0.465 for group 1, p = 0.715 for group 2 and p = 0.889 when analysed altogether).
Conclusions Both groups showed similar thickness increase when measured values (1.7 mm and 1.85 mm) were evaluated. The statistical dilemma showing no increase when groups analysed on their own was attributed to low number of participants. Biceps brachii stiffness showed no statistically significant change before and after training. However, when measured values were evaluated, there was a trend showing a decrease in stiffness of ischaemic group around 3.5 kPa and an increase in stiffness of classical hypertrophy group around 3 kPa. This may be statistically and clinically unimportant, but as well may show a beneficial effect for ischaemic training, contrary to beliefs that restricting blood flow may be harmful to soft tissues and effect their viscoelastic properties negatively. Further research should involve larger group of participants in order to analyse data with parametric tests.
References
Lowery RP, Joy JM, Loenneke JP, de Souza EO, Machado M, Dudeck JE, Wilson JM. Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training programme. Clin Physiol Funct Imaging 2014 Jul;34(4):317–21.
Wilson JM, Lowery RP, Joy JM, Loenneke JP, Walters JA, Amsden CE. Practical blood flow restriction training increases acute determinants of hypertrophy without increasing indices of muscle damage. J Strength Cond Res. 2013 Nov;27(11):3068–75.
Example axial B-mode image of the biceps brachii muscle. Note that the field of view is not filled due to low touching pressure, in order not to compress the muslce assuring precise measurement.
Example shear wave elastography measurement from a longitudinal image of the biceps brachii muscle