High intensity interval training does not impair strength gains in response to resistance training in premenopausal women.

PURPOSE: To compare the increases in upper- and lower-body muscle strength in premenopausal women performing resistance training (RT) alone or alongside concurrent high-intensity interval training (CT). METHODS: Sixteen women (26-40 years) were randomly assigned into two groups that performed either RT or CT. Both groups performed the same RT program; however, CT performed additional high-intensity interval training (HIIT) on a bicycle ergometer before RT. The study lasted 8 weeks and the participants were tested for ten repetition maximum (10RM) load in elbow flexion (barbell biceps curl) and knee extension exercises pre- and post-intervention. RT was performed with 10-12 repetitions to self-determined repetition maximum in the first four weeks and then progressed to 8-10. During CT, HIIT was performed before RT with six 1-min bouts at 7-8 of perceived subjective exertion (RPE) and then progressed to eight bouts at 9-10 RPE. RESULTS: Analysis of variance revealed significant increases in upper and lower body strength for both the RT and CT groups. Biceps barbell curl 10RM load increased from 12.9 ± 3.2 kg to 14 ± 1.5 kg in CT (p < 0.05) and from 13 ± 1.8 kg to 15.9 ± 2.5 kg in RT (p < 0.05), with no significant between-groups differences. Knee extension 10RM increase from 31.9 ± 11.6 kg to 37.5 ± 8.5 kg for CT (p < 0.05) and from 30.6 ± 8.6 kg to 41.2 ± 7.4 kg for RT (p < 0.05). CONCLUSION: In conclusion, performing HIIT on a cycle ergometer before resistance training does not seem to impair muscle strength increases in the knee extensors or elbow flexors of pre-menopausal women. This information should be considered when prescribing exercise sessions, since both activities may be combined without negative effects in muscle strength.

Impact of creatine supplementation in combination with resistance training on lean mass in the elderly.

BACKGROUND: Human ageing is a process characterized by loss of muscle mass, strength, and bone mass. We aimed to examine the efficacy of low-dose creatine supplementation associated with resistance training on lean mass, strength, and bone mass in the elderly. METHODS: This was a 12-week, parallel-group, double-blind, randomized, placebo-controlled trial. The individuals were randomly allocated into one of the following groups: placebo plus resistance training (PL + RT) and creatine supplementation plus resistance training (CR + RT) . The participants were assessed at baseline and after 12 weeks. The primary outcomes were lean mass and strength, assessed by dual energy X-ray absorptiometry (DXA) and ten-repetition maximal tests (10 RM), respectively. Secondary outcomes included the lumbar spine, right and left femoral neck, both femur and whole body bone mineral density (BMD), and whole body bone mineral content (BMC), assessed by DXA. RESULTS: The CR + RT group had superior gains in lean mass when compared with the PL + RT group (P = 0.02). Changes in the 10 RM tests in bench press and leg press exercises, body composition, BMD, and BMC of all assessed sites did not significantly differ between the groups (P > 0.05). CONCLUSIONS: Twelve weeks of low-dose creatine supplementation associated with resistance training resulted in increases in lean mass in the elderly.