This study examined whether the existing duration of type-2 diabetes influenced patient responses to progressive resistance training. Twenty-six women with type-2 diabetes were stratified into short- ...(3 ± 2 years; n = 12) or long-standing (10 ± 3 years; n = 14) disease groups. Patients participated in a high daily or high weekly frequency elastic band resistance training program that consisted of 2 daily sessions, 5 d·wk for 12 weeks. Glucose control, body composition, and physical function were evaluated pre- and posttraining. No significant diabetes duration × training interactions were detected for blood markers of glucose control (p > 0.05); however, there were significant main effects of training driven by comparable improvements in both cohorts (hemoglobin A1c, -13 to 18%; fasting glucose, -23 to 31%; postprandial glucose, -36 to 40%; insulin, -34 to 40%; C-peptide, -38 to 51%; p ≤ 0.05). Anthropometrics and body composition were also favorably modified in both the groups after training (weight, -5 to 9%; body mass index, -6 to 9%; waist-to-hip ratio, -3 to 5%; percent fat, -14 to 20%; p ≤ 0.05). Likewise, indices of physical function improved in both the groups after training (bicep curl repetitions, +15-33%; sit-and-stand repetitions, +45-47%; p ≤ 0.05). A few exceptions were noted in which patients with long-standing disease demonstrated greater pre-to-post gains (p ≤ 0.05) in grip strength (+11-13%) and peak exercise time (+19%) and load (+21%) during graded exercise, whereas those with shorter disease duration did not. Overall, these data suggest that patients with a long history of diabetes respond positively to resistance training and in a manner comparable to their recently diagnosed counterparts. Therefore, current inactivity in patients with long-standing disease should not deter from beginning an exercise program.
A single bout of unaccustomed exercise confers protective effect against muscle damage from a subsequent bout of similar activity, that is, repeated bout effect (RBE). It remains unknown whether ...varying muscle-specific exercise between sessions alters the magnitude of the RBE. This study examined the effects of muscle-specific exercise variation between consecutive sessions on the RBE. Twenty untrained males (21 ± 2 years) were assigned to one of 2 groups (n = 10 per group): (a) 2 sessions of incline curls, Fixed Exercise or (b) 1 session of incline curls followed by 1 session of preacher curls, Varied Exercise, with 7 days between sessions. Subjects performed 5 sets of 6 repetitions at ∼50% of maximal isometric elbow flexor strength during each session. Changes in maximal voluntary isometric and isokinetic torque, range of motion, muscle soreness, and serum creatine kinase were measured before, immediately after, and 24, 48, 72, and 96 hours after each exercise session, and the changes were compared between bouts and between groups. There were significant time effects (p < 0.05) for isometric maximal voluntary contraction, concentric maximal voluntary contraction, range of motion, and muscle soreness during sessions 1 and 2 with no between-group differences. Both groups demonstrated a significantly faster recovery of range of motion and soreness to baseline levels after session 2 compared with session 1. Overall, our findings suggest that incline curls conferred a protective effect during subsequent preacher curls in a similar way to repeating incline curls; therefore, the RBE was not exercise specific.
Eccentric muscle actions cause muscle damage and lead to delayed-onset muscle soreness (DOMS), which may impair performance. The purpose of this study was to examine the effect of DOMS on elbow ...flexion strength and rate of velocity development (RVD). Nineteen college male subjects performed 6 tests (pre- and posteccentric and every 24 hours for 4 days). In the preeccentric tests, each subject reported his arm pain and then did 5 concentric repetitions of elbow flexion/extension on an isokinetic dynamometer at 240 degrees x s(-1). Each subject then completed 6 sets of 10 eccentric elbow flexion actions at 30 degrees x s(-1) and finished with a posteccentric test with another 5 concentric repetitions at 240 degrees x s(-1). On days 1-4, each subject reported his arm pain and then did 5 more repetitions at 240 degrees x s(-1). Analysis was performed on the values for DOMS, peak torque (PT), and RVD. For DOMS, scores on the posteccentric test (2.34 +/- 2.53), day 1 (3.18 +/- 2.18), day 2 (3.21 +/- 2.91), day 3 (1.81 +/- 1.78), and day 4 (1.02 +/- 1.30) were all significantly (p < 0.05) greater than the preeccentric scores (0.00 +/- 0.00). For PT, the scores on the posteccentric test (22.40 +/- 8.87 ft x lb(-1)) and day 1 (23.88 +/- 9.00 ft x lb(-1)) were both significantly less than on the preeccentric test (29.56 +/- 8.42 ft x lb(-1)). The RVD scores on the posteccentric test (1505.73 +/- 462.12 d x s(-1) x s(-1)), day 1 (1571.55 +/- 475.99 d x s(-1) x s(-1)), and day 2 (1546.99 +/- 494.52 d x s(-1) x s(-1)) were all significantly less than on the preeccentric test (1719.86 +/- 473.18 d x s(-1) x s(-1)). This suggests that muscle damage may cause significant decreases in elbow flexion concentric strength and RVD even as DOMS remains elevated.
Surfing is a dynamic sport that is multidirectional in nature and requires peak performance in variable ocean conditions. Its growing popularity among the female population has stirred curiosity as ...to whether women can and will 1 day face their male counterparts in head-to-head competition at the top levels. The purpose of this study was to examine male and female differences in performance of a simulated surfing pop-up movement. Forty recreationally trained surfers (20 men and 20 women) were instructed to lie prone on a force plate, in the pop-up position (similar to a push-up), with only their hands in contact with the plate. A velocity transducer was attached to their back via an adjustable strap around their upper trunk. They completed 3 pop-ups as explosively as possible by pushing forcefully with their hands and jumping to their feet. Absolute and relative force and power were measured. Results demonstrated that men exhibited significantly (p < 0.05) greater relative force (M = 9.56 ± 1.25 N·kg⁻¹, W = 8.15 ± 0.98) and relative power (M = 16.39 ± 4.22 W·kg⁻¹, W = 9.98 ± 2.58) when compared to women. These findings demonstrate that men produce greater force and power than do women even relative to body weight when performing a simulated surfing pop-up movement. It appears that women may be at a disadvantage in regards to peak performance when compared to their male counterparts in the surfing pop-up movement. Therefore, women should train for both maximum and explosive upper-body strength in addition to their time spent surfing.
Tran, TT, Brown, LE, Coburn, JW, Lynn, SK, Dabbs, NC, Schick, MK, Schick, EE, Khamoui, AV, Uribe, BP, and Noffal, GJ. Effects of different elastic cord assistance levels on vertical jump. J Strength ...Cond Res 25(12): 3472-3478, 2011-Currently, little research has been conducted using body weight reduction (BWR) as a means to enhance vertical jump. The purpose of this study was to determine the effects of different elastic cord assistance levels on vertical jump height (JH), takeoff velocity (TOV), relative ground reaction force (rGRF), relative impact force (RIF), and descent velocity (DV). Thirty recreationally trained college men and women (M = 15, W = 15) completed 3 testing sessions consisting of 5 conditions: 0, 10, 20, 30, and 40% BWR. In all BWR conditions, the subjects wore a full body harness while being attached to 2 elastic cords suspended from the ceiling and a linear velocity transducer. They then performed 3 maximal countermovement jumps with arm swing on a force plate. The results indicated no interaction of condition by sex for any variable; however, there was a significant (p < 0.05) main effect for condition for each variable. The JH significantly increased across all conditions (0%: 43.73 ± 1.62 cm, 40%: 64.77 ± 2.36 cm). The TOV at 30% (2.73 ± 0.34 m·s) was significantly greater than that at 0% (2.59 ± 0.39 m·s) and 10% (2.63 ± 0.34 m·s), whereas that at 40% (2.79 ± 0.43 m·s) was significantly greater than that at >0, 10, and 20%. The rGRF at 30% (18.62 ± 4.35 N·kg) was significantly greater than that at >0, 10, and 20%, whereas that at 40% (21.38 ± 5.21 N·kg) was significantly greater than in all conditions. The RIF at 20, 30, and 40% (40%: 61.60 ± 18.53 N·kg) was significantly greater than that at 0% (44.46 ± 9.12 N·kg). The DV at 20% (2.61 ± 0.31 m·s) was significantly greater than at 10%, whereas those at 30 and 40% (2.8 ± 0.41 m·s) were significantly greater than at 0, 10, and 20%. These results demonstrate that using different elastic cord levels to reduce body weight appears effective for increasing ascent and descent force and velocity variables. Future research should investigate greater BWR% and chronic training.
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Rationale
Myostatin (Mstn) is a transforming growth factor‐β superfamily member that contributes to regulation of skeletal muscle mass. Myostatin also has a role in regulating ...metabolism: knockout reduces capacity for mitochondrial oxidative phosphorylation (OXPHOS), while overexpression increases the proportion of mitochondria‐rich oxidative fibers. Consumption of a high‐fat diet (HF) adversely affects human health by inducing metabolic disease and mitochondrial dysfunction in skeletal muscle. What has not been well‐established is if the oxidative features generated by transgenic overexpression of Mstn protects against HF. This study aimed to determine whether muscle‐specific overexpression of myostatin ameliorates the deleterious effects of HF on mitochondrial function.
Methods
One year old male mice with constitutive genetic modification of Mstn expression (KO, knock‐out; TG, transgenic overexpression) were kept on HF for 4 weeks (KO‐HF, TG‐HF, n=6/group). Age‐matched wild type mice (WT) were fed a regular diet (WT‐RG, n=8) or HF (WT‐HF, n=7). Fiber bundles from the medial gastrocnemius were saponin‐permeabilized and mitochondrial function measured by high‐resolution respirometry. LEAK (non‐phosphorylating O
2
flux with saturating malate+palmitoylcarnitine), OXPHOS capacity (O
2
flux with saturating complex I+II substrates), and electron transport system capacity (ETS; maximal uncoupled O
2
flux with FCCP) were measured.
Results
OXPHOS capacity tended to be greater in WT‐HF vs. WT‐RG (66±21 vs. 54±7 pmol/s/mg, p=0.12). ETS capacity was significantly greater in WT‐HF vs. WT‐RG (86±23 vs. 65±11 pmol/s/mg, p<0.05). LEAK was greater in KO‐HF and TG‐HF, vs. WT‐HF (p<0.05). OXPHOS and ETS capacity were significantly lower (~40%) in both KO‐HF and TG‐HF vs. WT‐HF (p<0.05), and not different from WT‐RG (p>0.05). The coupling control ratio (OXPHOS/ETS) in KO‐HF was greater (1.03±0.17, p<0.05) than all other groups (TG‐HF 0.77±0.09, WT‐HF 0.79±0.11, WT‐RG 0.83±0.08, p>0.05). Flux control ratio for complex I was lower in KO‐HF (0.49±0.08) and greater in TG‐HF (0.65±0.08) when compared to WT‐HF (0.56±0.03, p<0.05).
Conclusions
Mitochondrial respiration increased following HF, a possible compensatory response to increased reactive oxygen species. Interestingly, myostatin knockout and overexpression each decreased absolute muscle OXPHOS and ETS capacity to that of WT‐RG, which indicates an attenuated mitochondrial adaptation to the HF diet insult. With increasing uncoupling, OXPHOS approaches ETS; therefore the increased coupling control ratio for KO‐HF may reflect increased energy expenditure not available for oxidative phosphorylation. The preserved coupling and complex I control ratios for TG‐HF may therefore indicate a better maintenance of phosphorylation efficiency in the face of the HF diet. Whether myostatin overexpression can protect against the deleterious effects of a high fat diet deserves further investigation.
Support or Funding Information
NIH/NIGMS SC1GM089648 and Pulmonary Education and Research Foundation
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β‐hydroxy‐β‐methylbutyrate (HMB) has shown to attenuate loss of muscle mass and function. However, the efficacy of HMB during catabolism generated by prolonged exercise with calorie ...restriction has yet been addressed. Therefore, the present study investigated the impact of HMB on myofiber cross sectional area (CSA) and molecular regulators during a 6‐wk normal or catabolic condition. C57BL/6 male mice (Age= 6 wks) were divided into 4 groups (10/group): ALT=ad libitum+trained (1h/d for 3d/wk), ALTH=ALT+HMB (0.5 g/kg BW/day), C=caloric restricted (−30%)+trained (6hrs/d, 6d/wk) and CH=C+HMB. After the experimental period, the gastrocnemius muscles were isolated and analyzed histologically for myofiber number and CSA. Protein levels of atrogin‐1, myogenin, and phosphorylated Akt (pAkt) were determined by western blot. One‐way ANOVA was used and significance was set at p<0.05. Mean myofiber CSA (μm2) of the gastrocnemius in C was significantly lower than the ALT and ALTH (−38%), and CH (−35%), while the fiber number per field CSA was 35% higher in C than CH. Myogenin levels were significantly lower only in C compared to ALT and ALTH, while no group differences were detected for atrogin‐1 and pAkt. Our findings demonstrate the potential mechanisms of HMB action in enhancing regenerative capacity and attenuating the loss of myofiber CSA during prolonged exercise with low calorie intake.
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