Abstract
We compared the effects of aerobic high-intensity training (HIT) and isoinertial resistance training (IRT) on the strength, mass, architecture, intermuscular adipose tissue (IMAT) quality, and neuromuscular activation of the quadriceps in elderly subjects. Twelve healthy men (69.3 ± 4.2 years; 77.8 ± 10.4 kg; 1.72 ± 0.05 m) were exposed to 8 weeks of HIT (7 × 2-min cycling repetitions at 90% of O2peak, 3 times/week) and, after 4 months (detraining), to IRT (4 × 7 maximal concentric–eccentric knee extensions, 3 times/week). Before and after trainings, we measured knee extension isometric (TMVC) and dynamic (TC) maximal concentric torque, anatomical cross-sectional area (ACSA) at 25, 50, and 75% of femur length, quadriceps volume (Vol), IMAT, pennation angle (θp) of the fibers from the vastus lateralis, and voluntary activation (%Act). TMVC and TC were significantly larger only after IRT (P = 0.008); IRT was able to elicit a greater increase of ACSA than HIT; Vol increases similarly and significantly after HIT and IRT (P = 0.003–0.001); IMAT at 50% of femur length decreased after both HIT and IRT (P = 0.001–0.003); physiological cross-sectional area (PCSA) was larger after IRT than before (P = 0.025); specific torque did not change throughout the study (45.5 N cm–2 ± 12.0); %Act of the quadriceps was significantly affected only by IRT (P = 0.011). Both HIT and IRT are able to elicit beneficial modifications of muscular mass, architecture, and quality (reducing IMAT) in elderly subjects in connection with an amelioration of strength. HIT and IRT caused a homogeneous increase of ACSA and of Vol of the quadriceps. PCSA increases, but specific strength per unit of PCSA did not change. The increases of functional torque seemed to be attributed to a parallel increase of %Act and muscle hypertrophy only after IRT. Data suggest that IMAT may be a prominent indicator to track metabolic-dependent activity and skeletal muscle quality.
Highlights
In elderly people, the loss of muscle mass and strength has a negative impact on their daily life autonomy, balance, and gait (Narici and Maffulli, 2010)
isoinertial resistance training (IRT) was followed by a significant increase of anatomical cross-sectional area (ACSA) at all the three evaluated % of femur length [at 25%: plus 3.19 cm2 ± 1.24; (P = 0.001; 95% CI of diff: 2.40–3.99; d: 2.57); at 50%: plus 3.03 cm2 ± 3.04 (P = 0.005; 95% CI of diff: 1.10– 4.96; d: 1.00); at 75%: plus 3.40 cm2 ± 3.21 (P = 0.004; 95% CI of diff: 1.36–5.44; d: 1.06)] (Figure 1)
Ii) intermuscular adipose tissue (IMAT) at 50% of femur length decreased after both trainings, in particular after IRT, and the removal of IMAT did not change the pattern of the percent change of ACSA after trainings, it turned out to be larger than the ones calculated including IMAT area; iii) θp increased both after high-intensity training (HIT) and IRT; physiological cross-sectional area (PCSA) turned out to be larger only after IRT; the changes in PCSA and in torque resulted in constant value of specific strength per unit of PCSA; iv) %percent neuromuscular activation (Act) of the quadriceps was only greater after the IRT and the increments of strength observed after IRT seem to be predicted by the consensual increases of ACSA and %Act
Summary
The loss of muscle mass and strength has a negative impact on their daily life autonomy, balance, and gait (Narici and Maffulli, 2010). Sarcopenia (the progressive loss of muscle mass and strength with age), has functional and metabolic consequences: the progressive decrease of lean body mass is mirrored by the decay of resting metabolic rate (Narici and Maffulli, 2010), and it implies a decrease of daily physical activities and of total energy expenditure (Vaughan et al, 1991; Goran and Poehlman, 1992) Both these factors predispose elderly people to accumulate visceral and total body fat (Kohrt and Holloszy, 1995) and to develop poor insulin sensitivity and increased post-prandial hyperglycemia. IMAT, which might be viewed as a peripheral ectopic fat depot, surrounds and infiltrates muscle groups with which it shares a direct vascular connection. In spite of its role, thigh IMAT has not been widely studied
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