Daniel Hackett

Exercise and non-alcoholic fatty liver disease: a systematic review and meta-analysis.

BACKGROUND & AIMS Exercise is an integral component of lifestyle intervention aimed at weight loss, but an independent benefit of exercise in NAFLD has also been suggested. METHODS We aimed to evaluate the efficacy of aerobic exercise and/or progressive resistance training for the modulation of liver fat and alanine aminotransferase (ALT) levels in adults. Relevant databases were searched up to August 2011 for controlled trials, which compared regular exercise vs. a non-exercise control on change in liver fat and/or ALT. RESULTS Of the 16,822 studies from the initial search, 12 were included. There was a significant pooled effect size (ES) for the comparison between exercise therapy vs. control (ES=-0.37, 95% CI: -0.06 to -0.69; p=0.02), but only when interventions which compared combined exercise and diet vs. diet-alone and achieved substantial weight loss, were omitted. The benefit of exercise on liver fat occurred with minimal or no weight loss. There was no effect of exercise alone vs. control on ALT (ES=-0.15, 95% CI: 0.14 to -0.45; p=0.32). CONCLUSIONS Individual reports of exercise interventions often have low sample sizes and insufficient power to detect clinically meaningful hepatic benefits. By pooling current research, we show clear evidence for a benefit of exercise therapy on liver fat but not ALT levels. This benefit is apparent with minimal or no weight loss and at exercise levels below current exercise recommendations for obesity management. Given the paucity of current treatment options, exercise provides a valid, low-cost therapy for disorders characterised by fatty liver.

Effect of aerobic exercise training dose on liver fat and visceral adiposity

BACKGROUND & AIMS Aerobic exercise reduces liver fat and visceral adipose tissue (VAT). However, there is limited data from randomized trials to inform exercise programming recommendations. This study examined the efficacy of commonly prescribed exercise doses for reducing liver fat and VAT using a randomized placebo-controlled design. METHODS Inactive and overweight/obese adults received 8 weeks of either; i) low to moderate intensity, high volume aerobic exercise (LO:HI, 50% VO 2peak, 60 min, 4d/week); ii) high intensity, low volume aerobic exercise (HI:LO, 70% VO 2peak, 45 min, 3d/week); iii) low to moderate intensity, low volume aerobic exercise (LO:LO, 50% VO 2peak, 45 min, 3d/week); or iv) placebo (PLA). Liver fat (spectroscopy) and VAT (magnetic resonance imaging) were measured before and after intervention. RESULTS Forty-seven of the 48 (n = 12 in each group) participants completed the trial. There were no serious adverse events. There was a significant change in group × time interaction in liver fat, which reduced in HI:LO by 2.38 ± 0.73%, in LO:HI by 2.62 ± 1.00%, and in LO:LO by 0.84 ± 0.47% but not in PLA (increase of 1.10 ± 0.62%) (p = 0.04). There was a significant reduction in VAT in HI:LO (-258.38 ± 87.78 cm(3)), in LO:HI (-386.80 ± 119.5 cm(3)), and in LO:LO (-212.96 ± 105.54 cm(3)), but not in PLA (92.64 ± 83.46 cm(3)) (p = 0.03). There were no significant differences between the dose or intensity of the exercise regimen and reductions in liver fat or VAT (p > 0.05). CONCLUSION The study found no difference in efficacy of liver fat reduction by either aerobic exercise dose or intensity. All of the aerobic exercise regimens employed reduced liver fat and VAT by a small amount without clinically significant weight loss.

Training practices and ergogenic aids used by male bodybuilders.

Abstract Hackett, DA, Johnson, NA, and Chow, C-M. Training practices and ergogenic aids used by male bodybuilders. J Strength Cond Res 27(6): 1609–1617, 2013—Bodybuilding involves performing a series of poses on stage where the competitor is judged on aesthetic muscular appearance. The purpose of this study was to describe training practices and ergogenic aids used by competitive bodybuilders and to determine whether training practices comply with current recommendations for muscular hypertrophy. A web-based survey was completed by 127 competitive male bodybuilders. The results showed that during the off-season phase of training (OFF), the majority of respondents performed 3–6 sets per exercise (95.3%), 7–12 repetition maximum (RM) per set (77.0%), and 61- to 120-seconds recovery between sets and exercises (68.6%). However, training practices changed 6 weeks before competition (PRE), where there was an increased number of respondents who reported undertaking 3–4 sets per exercise at the expense of 5–6 sets per exercise (p < 0.001), an increase in the number reporting 10–15RM per set from 7–9RM per set (p < 0.001), and an increase in the number reporting 30–60 seconds vs. 61–180 seconds recovery between sets and exercises (p < 0.001). Anabolic steroid use was high among respondents competing in amateur competitions (56 of 73 respondents), whereas dietary supplementation was used by all respondents. The findings of this study demonstrate that competitive bodybuilders comply with current resistance exercise recommendations for muscular hypertrophy; however, these changed before competition during which there is a reduction resistance training volume and intensity. This alteration, in addition to an increase in aerobic exercise volume, is purportedly used to increase muscle definition. However, these practices may increase the risk of muscle mass loss in natural compared with amateur bodybuilders who reportedly use drugs known to preserve muscle mass.

The Efficacy of Injury Prevention Programs in Adolescent Team Sports A Meta-analysis

Background: Intensive sport participation in childhood and adolescence is an established cause of acute and overuse injury. Interventions and programs designed to prevent such injuries are important in reducing individual and societal costs associated with treatment and recovery. Likewise, they help to maintain the accrual of positive outcomes from participation, such as cardiovascular health and skill development. To date, several studies have individually tested the effectiveness of injury prevention programs (IPPs). Purpose: To determine the overall efficacy of structured multifaceted IPPs containing a combination of warm-up, neuromuscular strength, or proprioception training, targeting injury reduction rates according to risk exposure time in adolescent team sport contexts. Study Design: Systematic review and meta-analysis. Methods: With established inclusion criteria, studies were searched in the following databases: Cochrane Central Register of Controlled Trials, MEDLINE, SPORTDiscus, Web of Science, EMBASE, CINAHL, and AusSportMed. The keyword search terms (including derivations) included the following: adolescents, sports, athletic injuries, prevention/warm-up programs. Eligible studies were then pooled for meta-analysis with an invariance random-effects model, with injury rate ratio (IRR) as the primary outcome. Heterogeneity among studies and publication bias were tested, and subgroup analysis examined heterogeneity sources. Results: Across 10 studies, including 9 randomized controlled trials, a pooled overall point estimate yielded an IRR of 0.60 (95% CI = 0.48-0.75; a 40% reduction) while accounting for hours of risk exposure. Publication bias assessment suggested an 8% reduction in the estimate (IRR = 0.68, 95% CI = 0.54-0.84), and the prediction interval intimated that any study estimate could still fall between 0.33 and 1.48. Subgroup analyses identified no significant moderators, although possible influences may have been masked because of data constraints. Conclusion: Compared with normative practices or control, IPPs significantly reduced IRRs in adolescent team sport contexts. The underlying explanations for IPP efficacy remain to be accurately identified, although they potentially relate to IPP content and improvements in muscular strength, proprioceptive balance, and flexibility. Clinical Relevance: Clinical practitioners (eg, orthopaedics, physical therapists) and sports practitioners (eg, strength and conditioners, coaches) can respectively recommend and implement IPPs similar to those examined to help reduce injury rates in adolescent team sports contexts.

A novel scale to assess resistance-exercise effort

Abstract In this study, we examined the validity of a novel subjective scale for assessing resistance-exercise effort. Seventeen male bodybuilders performed five sets of 10 repetitions at 70% of one-repetition maximum, for the bench press and squat. At the completion of each set, participants quantified their effort via the rating of perceived exertion (RPE) and novel estimated-repetitions-to-failure scales, and continued repetitions to volitional exhaustion to determine actual-repetitions-to-failure. There were high correlations between estimated- and actual-repetitions-to-failure across sets for the bench press and squat (r ≥ 0.93; P < 0.05). During sets 3, 4, and 5, estimated-repetitions-to-failure predicted the number of repetitions to failure for the bench press and squat, as indicated by smaller effect sizes for differences (ES = 0.37–0.0). The estimated-repetitions-to-failure scale was reliable as indicated by high intraclass correlation coefficients (≥0.92) and narrow 95% limits of agreement (≤0.63 repetitions) for both the bench press and squat. Despite high correlations between RPE and actual-repetitions-to-failure (P < 0.05), RPE at volitional fatigue was less than maximal for both exercises. Our results suggest that the estimated-repetitions-to-failure scale is valid for predicting onset of muscular failure, and can be used for the assessment and prescription of resistance exercise.

The Effect of Regular Exercise on Insulin Sensitivity in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

The purpose of this study was to examine the effect of regular exercise training on insulin sensitivity in adults with type 2 diabetes mellitus (T2DM) using the pooled data available from randomised controlled trials. In addition, we sought to determine whether short-term periods of physical inactivity diminish the exercise-induced improvement in insulin sensitivity. Eligible trials included exercise interventions that involved ≥3 exercise sessions, and reported a dynamic measurement of insulin sensitivity. There was a significant pooled effect size (ES) for the effect of exercise on insulin sensitivity (ES, –0.588; 95% confidence interval [CI], –0.816 to –0.359; P<0.001). Of the 14 studies included for meta-analyses, nine studies reported the time of data collection from the last exercise bout. There was a significant improvement in insulin sensitivity in favour of exercise versus control between 48 and 72 hours after exercise (ES, –0.702; 95% CI, –1.392 to –0.012; P=0.046); and this persisted when insulin sensitivity was measured more than 72 hours after the last exercise session (ES, –0.890; 95% CI, –1.675 to –0.105; P=0.026). Regular exercise has a significant benefit on insulin sensitivity in adults with T2DM and this may persist beyond 72 hours after the last exercise session.

Systematic review of exercise for Charcot-Marie-Tooth disease

Charcot‐Marie‐Tooth disease (CMT) is a slowly progressive hereditary degenerative disease and one of the most common neuromuscular disorders. Exercise may be beneficial to maintain strength and function for people with CMT, however, no comprehensive evaluation of the benefits and risks of exercise have been conducted. A systematic review was completed searching numerous electronic databases from earliest records to February 2015. Studies of any design including participants of any age with confirmed diagnosis of CMT that investigated the effects of exercise were eligible for inclusion. Of 13,301 articles identified following removal of duplicates, 11 articles including 9 unique studies met the criteria. Methodological quality of studies was moderate, sample sizes were small, and interventions and outcome measures used varied widely. Although the majority of the studies identified changes in one or more outcome measurements across exercise modalities, the majority were non‐significant, possibly due to Type II errors. Significant effects described included improvements in strength, functional activities, and physiological adaptations following exercise. Despite many studies showing changes in strength and function following exercise, findings of this review should be met with caution due to the few studies available and moderate quality of evidence. Well‐powered studies, harmonisation of outcome measures, and clearly described interventions across studies would improve the quality and comparability of the evidence base. The optimal exercise modality and intensity for people with CMT as well as the long‐term safety of exercise remain unclear.

The Valsalva Maneuver: Its Effect on Intra-abdominal Pressure and Safety Issues During Resistance Exercise

Abstract Hackett, DA and Chow, C-M. The Valsalva maneuver: its effect on intra-abdominal pressure and safety issues during resistance exercise. J Strength Cond Res 27(8): 2338–2345, 2013—During resistance exercise, a brief Valsalva maneuver (VM) is unavoidable when lifting heavy loads (>80% of maximal voluntary contraction) or when lifting lighter loads to failure. It has been proposed that the performance of the VM during resistance exercise increases the stability of the spine because of augmented intra-abdominal pressure (IAP). However, resistance trainers are often advised to avoid the VM during resistance exercise because of potential adverse vascular events. The aim of this review was to establish the effect of the VM on IAP and to evaluate if the VM during resistance exercise is a safe practice. Relevant databases were searched to examine the effect of the VM on: (a) IAP and (b) hemodynamics during resistance exercise and reported adverse events. The data show that the VM alone increases IAP and that the VM augment IAP during various resistance exercises. An incremental rise in IAP was observed as the lifting intensity and effort increased, with IAP tending to be lower compared with peak IAP from the VM alone. The VM was associated with an increase in blood pressure during resistance exercise, but the VM alone was associated with greater hemodynamic changes. In conclusion, the VM effectively increases IAP, which may assist with spine stability and trunk rigidity during resistance exercise. The health risks associated with the VM during resistance exercise remain unconfirmed.

Olympic weightlifting training improves vertical jump height in sportspeople: A systematic review with meta-analysis

Purpose This systematic review was conducted to evaluate the effect of Olympic weightlifting (OW) on vertical jump (VJ) height compared to a control condition, traditional resistance training and plyometric training. Methods Five electronic databases were searched using terms related to OW and VJ. Studies needed to include at least one OW exercise, an intervention lasting ≥6 weeks; a comparison group of control, traditional resistance training or plyometric training; and to have measured VJ height. The methodological quality of studies was assessed using the Downs and Black Checklist. Random and fixed effects meta-analyses were performed to pool the results of the included studies and generate a weighted mean effect size (ES). Results Six studies (seven articles) were included in the meta-analyses and described a total of 232 participants (175 athletes and 57 physical education students) with resistance training experience, aged 19.5±2.2 years. Three studies compared OW versus control; four studies compared OW versus traditional resistance training; and three studies compared OW versus plyometric training. Meta-analyses indicated OW improved VJ height by 7.7% (95% CI 3.4 to 5.4 cm) compared to control (ES=0.62, p=0.03) and by 5.1% (95% CI 2.2 to 3.0 cm) compared to traditional resistance training (ES=0.64 p=0.00004). Change in VJ height was not different for OW versus plyometric training. Conclusions OW is an effective training method to improve VJ height. The similar effects observed for OW and plyometric training on VJ height suggests that either of these methods would be beneficial when devising training programmes to improve VJ height.

Effects of a Modified German Volume Training Program on Muscular Hypertrophy and Strength.

Abstract Amirthalingam, T, Mavros, Y, Wilson, GC, Clarke, JL, Mitchell, L, and Hackett, DA. Effects of a modified German volume training program on muscular hypertrophy and strength. J Strength Cond Res 31(11): 3109–3119, 2017—German Volume Training (GVT), or the 10 sets method, has been used for decades by weightlifters to increase muscle mass. To date, no study has directly examined the training adaptations after GVT. The purpose of this study was to investigate the effect of a modified GVT intervention on muscular hypertrophy and strength. Nineteen healthy men were randomly assign to 6 weeks of 10 or 5 sets of 10 repetitions for specific compound resistance exercises included in a split routine performed 3 times per week. Total and regional lean body mass, muscle thickness, and muscle strength were measured before and after the training program. Across groups, there were significant increases in lean body mass measures, however, greater increases in trunk (p = 0.043; effect size [ES] = −0.21) and arm (p = 0.083; ES = −0.25) lean body mass favored the 5-SET group. No significant increases were found for leg lean body mass or measures of muscle thickness across groups. Significant increases were found across groups for muscular strength, with greater increases in the 5-SET group for bench press (p = 0.014; ES = −0.43) and lat pull-down (p = 0.003; ES = −0.54). It seems that the modified GVT program is no more effective than performing 5 sets per exercise for increasing muscle hypertrophy and strength. To maximize hypertrophic training effects, it is recommended that 4–6 sets per exercise be performed, as it seems gains will plateau beyond this set range and may even regress due to overtraining.