Author(s): ICHINOSE, H., MAEO, S.1, KINOSHITA, M.1, KOBAYASHI, Y.1, EIHARA, Y.1, NISHIZAWA, N.1, KUSAGAWA, Y.1, SUGIYAMA, T.1, KANEHISA, H.2, ISAKA, T.1 , Institution: RITSUMEIKAN UNIVERSITY, Country: JAPAN, Abstract-ID: 2537

INTRODUCTION:
Spot reduction refers to the conception of localized loss of subcutaneous adipose tissue (SAT) due to exercise of muscles in the same area [1]. Although the common belief is that the spot reduction does not occur as a result of an exercise program, the evidence is insufficient and thus this common belief is controversial. Resistance training can be classified into either single- or multi-joint exercises, and exercise-dependent muscle activation and muscle hypertrophy has been reported [2]. However, the effects of these exercises on the loss of SAT have not been well studied, and little is known about whether the localized loss of SAT occurs after each exercise. This study aimed to investigate the quantitative changes in the SAT of the hip and thigh areas resulting from each of single- (knee extension; KE) and multi-joint (leg press; LP) resistance exercises.
METHODS:
Seventeen untrained healthy young adults (11 males and 6 females) performed single-joint KE in one leg and multi-joint LP in the other leg at 70% of one repetition maximum (1RM) of the corresponding task. Each leg performed 5 sets of 10 repetitions per session, 2 sessions per week for 12 weeks. Before and after the intervention, the following variables were measured using magnetic resonance images from both KE and LP sides: the cross-sectional area (CSA) of the muscles in the hip (the total area of 4 individual muscles) at the level of the upper end of the greater trochanter and those in the midthigh (the total area of 12 individual muscles), and the SAT CSA at the same two levels.
RESULTS:
The muscle CSA in the hip significantly increased after the LP (p < 0.01) but not after the KE (p = 0.17), and the muscle CSA in the thigh significantly increased after both KE and LP (p < 0.01). The %change in the muscle CSA in the hip was greater for the LP than the KE (LP vs KE, +10.8% vs +3.6%, p < 0.01). In the thigh, no difference was observed in %change in the muscle CSA between LP and KE (+5.3% vs +4.2%, p = 0.14). The SAT CSA of the hip and thigh did not change in either training (p = 0.85-0.89), and no difference was observed in the %change in the SAT CSA between the two training tasks in either the hip (-0.3% vs -0.4%, p = 0.94) or thigh (-1.1% vs -0.3%, p = 0.56).
CONCLUSION:
After the intervention in this study, the exercise-dependent muscle hypertrophy was presented (LP: the hip and thigh, KE: the thigh only), but the SAT area did not significantly change in any exercise or site. This suggests that resistance training, inducing muscle hypertrophy, does not reduce the SAT at the trained area, and the localized loss of SAT due to resistance training does not occur.
[1] Kostek, M.A. et al. (2007) Sci Sports Exerc, 39(7): 1177-1185. [2] Gentil, P. et al. (2017) Sports Med, 47(5): 843-855.