P. Logan

Concurrent strength and endurance training: A review

AbstractConcurrent strength and endurance training appears to inhibit strength development when compared with strength training alone. Our understanding of the nature of this inhibition and the mechanisms responsible for it is limited at present. This is due to the difficulties associated with comparing results of studies which differ markedly in a number of design factors, including the mode, frequency, duration and intensity of training, training history of participants, scheduling of training sessions and dependent variable selection. Despite these difficulties, both chronic and acute hypotheses have been proposed to explain the phenomenon of strength inhibition during concurrent training. The chronic hypothesis contends that skeletal muscle cannot adapt metabolically or morphologically to both strength and endurance training simultaneously. This is because many adaptations at the muscle level observed in response to strength training are different from those observed after endurance training. The observation that changes in muscle fibre type and size after concurrent training are different from those observed after strength training provide some support for the chronic hypothesis. The acute hypothesis contends that residual fatigue from the endurance component of concurrent training compromises the ability to develop tension during the strength element of concurrent training. It is proposed that repeated acute reductions in the quality of strength training sessions then lead to a reduction in strength development over time. Peripheral fatigue factors such as muscle damage and glycogen depletion have been implicated as possible fatigue mechanisms associated with the acute hypothesis. Further systematic research is necessary to quantify the inhibitory effects of concurrent training on strength development and to identify different training approaches that may overcome any negative effects of concurrent training.

Concurrent Strength and Endurance Training: The Influence of Dependent Variable Selection

Twenty-six active university students were randomly allocated to resistance (R, n 5 9), endurance (E, n 5 8), and concurrent resistance and endurance (C, n 5 9) training con-ditions. Training was completed 3 times per week in all conditions, with endurance training preceding resistance training in the C group. Resistance training involved 4 sets of upper- and lower-body exercises with loads of 4–8 repetition maximum (RM). Each endurance training session consisted of five 5-minute bouts of incremental cycle exercise at between 40 and 100% of peak oxygen uptake (VO2peak). Parameters measured prior to and following training included strength (1RM and isometric and isokinetic [1.04, 3.12, 5.20, and 8.67 rad·s 21] strength), VO2peak and Wingate test performance (peak power output [PPO], average power, and relative power decline). Significant improvements in 1RM strength were observed in the R and C groups following training. VO2peak significantly increased in E and C but was significantly reduced in R after training. Effect size (ES) transformations on the other dependent variables suggested that performance changes in the C group were not always similar to changes in the R or E groups. These ES data suggest that statistical power and dependent variable selection are significant issues in enhancing our insights into concurrent training. It may be necessary to assess a range of performance parameters to monitor the relative effectiveness of a particular concurrent training regimen.

Resistance training frequency: strength and myosin heavy chain responses to two and three bouts per week

Abstract Seventeen subjects performed resistance training of the leg extensor and flexor muscle groups two (2/wk) or three (3/wk) times per week. Changes in the relative myosin heavy chain (MHC) isoform contents (I, IIa and IIx) of the vastus lateralis and isometric, isokinetic and squat-lift one-repetition maximum (1RM) strength were compared between conditions after both a common training period (6 weeks) and number of training sessions (18). After 6 weeks and 18 sessions (9 weeks for the 2/wk group), increments in 1RM strength for the 3/wk and 2/wk groups were similar [effect size (ES) differences ≈0.3, 3/wk > 2/wk], whereas the 2/wk group presented greater isokinetic (ES differences = 0.3–1.2) and isometric (ES differences ≈0.7) strength increases than the 3/wk condition. A significant (P < 0.05) increase in MHC IIa percentage was evident for the 2/wk group after 18 sessions. Both training groups exhibited a trend towards a reduction in the relative MHC IIx and an increase in MHC IIa contents (ES range = 0.5–1.24). However, correlations between changes in the strength and MHC profiles were weak (r2: 0.0–0.5). Thus, isometric and isokinetic strength responses to variations in training frequency differed from 1RM strength responses, and changes in strength were not strongly related to alterations in relative MHC content.

A comparison of the physiological response to simulated altitude exposure and r-HuEpo administration

Concerns have been raised about the morality of using simulated altitude facilities in an attempt to improve athletic performance. One assumption that has been influential in this debate is the belief that altitude houses simply mimic the physiological effects of illegal recombinant human erythropoietin (r-HuEpo) doping. To test the validity of this assumption, the haematological and physiological responses of 23 well-trained athletes exposed to a simulated altitude of 2650-3000 m for 11-23 nights were contrasted with those of healthy volunteers receiving a low dose (150 IU·kg-1 per week) of r-HuEpo for 25 days. Serial blood samples were analysed for serum erythropoietin and percent reticulocytes; maximal oxygen uptake ([Vdot]O2max) was assessed before and after r-HuEpo administration or simulated altitude exposure. The group mean increase in serum erythropoietin (422% for r-HuEpo vs 59% for simulated altitude), percent reticulocytes (89% vs 30%) and [Vdot]O2max (6.6% vs -2.0%) indicated that simulated altitude did not induce the changes obtained with r-HuEpo administration. Based on the disparity of these responses, we conclude that simulated altitude facilities should not be considered unethical based solely on the tenet that they provide an alternative means of obtaining the benefits sought by illegal r-HuEpo doping.

β-Hydrozy β-methylbutyrate (HMB) supplementation does not influence the urinary testosterone: Epitestosterone ratio in healthy males

Six healthy, recreationally active, males undertook two weeks supplementation with β-Hydroxy β-Methylbutyrate (HMB). Supplementation was in capsule form with 3 g consumed each day in three even doses of 1 g at main meals. Mid stream urine samples were collected prior to, as well as, after one and two weeks of supplementation and subsequently analysed for testosterone and epitestosterone. The testosterone: epitestosterone ratio was not affected by 2 weeks of HMB supplementation (mean±SD baseline 1.02±0.68; week one 0.98±0.61; week two 0.92±0.62). Our results support the claim that supplementation with HMB at the doses recommended will not influence the urinary testosterone: epitestosterone ratio and thus not breach doping policies of the International Olympic Committee for exogenous testosterone or precursor administration.

Musculoskeletal screening as a predictor of seasonal injury in elite Olympic class sailors

OBJECTIVES To investigate seasonal injury incidence and musculoskeletal screening as a predictor of injury in elite Olympic class sailors. DESIGN Prospective cohort study. METHODS A 12-month analysis of injury surveillance data was performed for elite Australian sailors (age=16-30 years, N=22). Pre-season musculoskeletal screening (incorporating mobility, stability and neural tests) and seasonal injury data were analysed for predictive relationships, and associations between potential predictor variables and injury status. RESULTS Injuries requiring medical attention occurred at a rate of 3.6 injuries/athlete, while injuries resulting in disability occurred at a rate of 0.6 injuries/athlete, with the lumbar spine the main site of injury (23% and 33%, respectively). Wrist and hand injury resulted in the highest number of days of disability (110 days), followed by injury to the lumbar spine (87 days). Across the season 75% of injuries to the lumbar spine occurred in the latter half of the season. The only screening measure predictive of injured/uninjured status was better left-sided single-leg decline-squat performance (OR=0.29; 95% CI=0.09-0.88; p=0.03), while increasing age was significantly (p=0.03) associated with thoracic (OR=1.48; 95% CI=1.03-2.12) and lumbar spine (OR=1.46; 95% CI=1.04-2.04) injury. CONCLUSIONS Though clinically useful, current screening protocols do not adequately assess the risk of seasonal injury in elite Olympic class sailors, and should be revised. Due to the increased risk of spinal injury and potential lost/modified participation in older Olympic class sailors, injury prevention activities should be individualised and age appropriate.