Aim To examine the effect of high‐intensity interval training (HIIT) on glucose clearance rates in skeletal muscle and explore the mechanism within the muscle. Methods Ten males with type 2 diabetes mellitus (T2DM) and ten matched healthy subjects performed 2 weeks of one‐legged HIIT (total of eight sessions, each comprised of 10 × 1 minute ergometer bicycle exercise at >80% of maximal heart rate, interspersed with one min of rest). Insulin sensitivity was assessed by an isoglycaemic, hyperinsulinaemic clamp combined with arteriovenous leg balance technique of the trained (T) and the untrained (UT) leg and muscle biopsies of both legs. Results Insulin‐stimulated glucose clearance in T legs was ~30% higher compared with UT legs in both groups due to increased blood flow in T vs UT legs and maintained glucose extraction. With each training session, muscle glycogen content decreased only in the training leg, and after the training, glycogen synthase and citrate synthase activities were higher in T vs UT legs. No major changes occurred in the expression of proteins in the insulin signalling cascade. Mitochondrial respiratory capacity was similar in T2DM and healthy subjects, and unchanged by HIIT. Conclusion HIIT improves skeletal muscle insulin sensitivity. With HIIT, the skeletal muscle of patients with T2DM becomes just as insulin sensitive as untrained muscle in healthy subjects. The mechanism includes oscillations in muscle glycogen stores and a maintained ability to extract glucose from the blood in the face of increased blood flow in the trained leg.
Aim & Methods: Extreme endurance exercise provides a valuable research model for understanding the adaptive metabolic response of older and younger individuals to intense physical activity. Here, we compare a wide range of metabolic and physiologic parameters in two cohorts of seven trained men, age 30 ± 5 years or age 65 ± 6 years, before and after the participants travelled ≈3000 km by bicycle over 15 days. Results: Over the 15-day exercise intervention, participants lost 2-3 kg fat mass with no significant change in body weight. VȮ 2 max did not change in younger cyclists, but decreased (p = 0.06) in the older cohort. The resting plasma FFA concentration decreased markedly in both groups, and plasma glucose increased See related editorial: Henriksson J. 2022. Extreme duration endurance exercise affects old and younger men differently-Older individuals experience a negative adaptive response affecting cardiovascular function. Acta Physiol (Oxf). e13843.
Introduction Maximal fat oxidation rate (MFO) is higher in aerobically fit vs. unfit young men, but this training related increase in MFO is attenuated in middle-aged men. Further, it has also been found that unfit men with obesity may have an elevated MFO compared to unfit normal-weight men. Aim/Hypothesis Based hereupon, we aimed to investigate whether a fitness related higher MFO were attenuated in middle-aged women compared to young women. Also, we aimed to investigate if unfit women with obesity have a higher MFO compared to unfit normal-weight women. We hypothezised that the training related elevated MFO was attenuated in middle-aged women, but that unfit women with obesity would have an elevated MFO compared to unfit normal-weight women. Methods We recruited a total of 70 women stratified into six groups: Young fit (n=12), young unfit (n=12) middle-aged fit (n=12), middle-aged unfit (n=12), unfit young women with obesity (n=12) and unfit middle-aged women with obesity (n=10). Body composition and resting blood samples were obtained and MFO was measured by a graded exercise test on a cycle ergometer via indirect calorimetry. Subsequently, a maximal exercise test was performed to establish V̇O2peak. Results Young and middle-aged fit women had a higher MFO compared to age-matched unfit women, and young fit women had a higher MFO compared to fit middle-aged women. Unfit women with obesity, independent of age, had a higher MFO compared to their normal-weight and unfit counterparts. Conclusion The training related increase in MFO seems maintained in middle-aged women and secondly, we find that unfit women with obesity, independent of age have a higher MFO compared to unfit normal-weight women.
Exercise is important for prevention of sarcopenia in the elderly population. We tested two training modalities, ascending or descending stair walking, representing concentric (CON) and eccentric (ECC) exercise, respectively. We also tested the effects of additional weight during eccentric exercise (ECC+). Thirty-two healthy men and women (70 ± 3 [mean ± SE] yrs.) were randomly assigned to CON, ECC, or ECC+ (carrying +15% of body weight in a vest) in a 3 (n = 32) or 6 (n = 21) week intervention (3 sessions/week). Data was analysed by mixed models approach. Rate of perceived exertion (RPE; Borg scale 6-20; mean values from 3 and 6 weeks) during training did not differ between CON (12.3 ± 0.4), ECC (11.5 ± 0.3), and ECC+ (11.7 ± 0.4). After 6 weeks, leg muscle mass increased more in ECC+ (+0.29 ± 0.09 kg) vs CON (+0.08 ± 0.05 kg) (P<0.05) but not different from ECC (+0.16 ± 0.06 kg). 6-minute walk test (6MWT) increased after 6 weeks more (P<0.05) in ECC+ (+85 ± 23 m) compared with ECC (+37 ± 13 m) and CON (+27 ± 12 m). Intramyocellular glycogen content increased from 359 ± 19 nmol/mg d.w. in CON (to 511 ± 65 and 471 ± 44 after 3 and 6 wks, respectfully (P<0.05)), but not in ECC (to 344 ± 28 after 6 weeks) or in ECC+ (to 389 ± 20 after 6 weeks). Conclusion: carrying extra weight while descending stair walking do not increase RPE, but the ECC+ training resulted in greater muscle responses compared with CON, but glycogen synthesis was stimulated only in CON. Descending stairs is a simple model for prevention and treatment of sarcopenia and the stimulus is enhanced by carrying extra weights.
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