We investigated whether sprint interval training (SIT) was a time-efficient exercise strategy to improve insulin sensitivity and other indices of cardiometabolic health to the same extent as traditional moderate-intensity continuous training (MICT). SIT involved 1 minute of intense exercise within a 10-minute time commitment, whereas MICT involved 50 minutes of continuous exercise per session. Sedentary men (27±8y; BMI = 26±6kg/m²) performed three weekly sessions of SIT (n = 9) or MICT (n = 10) for 12 weeks or served as non-training controls (n = 6). SIT involved 3x20-second ‘all-out’ cycle sprints (~500W) interspersed with 2 minutes of cycling at 50W, whereas MICT involved 45 minutes of continuous cycling at ~70% maximal heart rate (~110W). Both protocols involved a 2-minute warm-up and 3-minute cool-down at 50W. Peak oxygen uptake increased after training by 19% in both groups (SIT: 32±7 to 38±8; MICT: 34±6 to 40±8ml/kg/min; p<0.001 for both). Insulin sensitivity index (CS_I), determined by intravenous glucose tolerance tests performed before and 72 hours after training, increased similarly after SIT (4.9±2.5 to 7.5±4.7, p = 0.002) and MICT (5.0±3.3 to 6.7±5.0 x 10⁻⁴ min^-1 [μU/mL]^-1, p = 0.013) (p<0.05). Skeletal muscle mitochondrial content also increased similarly after SIT and MICT, as primarily reflected by the maximal activity of citrate synthase (CS; P<0.001). The corresponding changes in the control group were small for VO₂peak (p = 0.99), CS_I (p = 0.63) and CS (p = 0.97). Twelve weeks of brief intense interval exercise improved indices of cardiometabolic health to the same extent as traditional endurance training in sedentary men, despite a five-fold lower exercise volume and time commitment.

Of SIT to improve CRF. Methods Two separate studies, each consisting of an acute and chronic phase, were conducted in a total of 31 sedentary women (age = 24 ± 10 yr, body mass index = 23 ± 4 kg·m−2). Results The acute phase of study 1 established that the mean HR, blood [lactate], and RPE were similar when participants (n = 8) performed an SIT protocol that involved 3 × 20-s “all-out” efforts of either continuously ascending stairs or cycling. The chronic phase demonstrated that CRF, as determined by peak oxygen uptake (V˙O2peak), increased by 12% or ~1 MET (8.27 ± 1.05 to 9.25 ± 1.01 METs, P = 0.002) when participants (n = 12) performed the 3 × 20-s stair climbing protocol 3 d·wk−1 for 6 wk. The acute phase of study 2 established that HR and RPE were similar when participants (n = 11) performed three different stair climbing protocols: the 3 × 20-s continuous ascent model used in study 1 and two 3 × 60-s models of ascending and descending either one or two flights of stairs (P > 0.05). The chronic phase demonstrated that V˙O2peak increased by 7% (8.91 ± 1.30 to 9.51 ± 1.52 METs, P = 0.01) when the same group of participants performed the one-flight 3 × 60-s protocol 3 d·wk−1 for 6 wk. The Cederholm index determined from an oral glucose tolerance test was 57 ± 17 and 64 ± 21 mg·L−2·mmol−1·mU−1·min−1 before and after training, respectively (P = 0.056). Conclusion Brief, intense stair climbing is a practical, time-efficient strategy to improve CRF in previously untrained women....

Direct sampling of human skeletal muscle using the needle biopsy technique can facilitate insight into the biochemical and histological responses resulting from changes in exercise or feeding. However, the muscle biopsy procedure is invasive, and analyses are often expensive, which places pragmatic restraints on sample sizes. The unilateral exercise model can serve to increase statistical power and reduce the time and cost of a study. With this approach, 2 limbs of a participant are randomized to 1 of 2 treatments that can be applied almost concurrently or sequentially depending on the nature of the intervention. Similar to a typical repeated measures design, comparisons are made within participants, which increases statistical power by reducing the amount of between-person variability. A washout period is often unnecessary, reducing the time needed to complete the experiment and the influence of potential confounding variables such as habitual diet, activity, and sleep. Variations of the unilateral exercise model have been employed to investigate the influence of exercise, diet, and the interaction between the 2, on a wide range of variables including mitochondrial content, capillary density, and skeletal muscle hypertrophy. Like any model, unilateral exercise has some limitations: it cannot be used to study variables that potentially transfer across limbs, and it is generally limited to exercises that can be performed in pairs of treatments. Where appropriate, however, the unilateral exercise model can yield robust, well-controlled investigations of skeletal muscle responses to a wide range of interventions and conditions including exercise, dietary manipulation, and disuse or immobilization.

Widespread sampling of vertebrates, which comprise the majority of published animal mitochondrial genomes, has led to the view that mitochondrial gene rearrangements are relatively rare, and that gene orders are typically stable across major taxonomic groups. In contrast, more limited sampling within the Phylum Mollusca has revealed an unusually high number of gene order arrangements. Here we provide evidence that the lability of the molluscan mitochondrial genome extends to the family level by describing extensive gene order changes that have occurred within the Vermetidae, a family of sessile marine gastropods that radiated from a basal caenogastropod stock during the Cenozoic Era.