Christian Lorenzen

Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study

Background/aim To investigate the role of eccentric knee flexor strength, between-limb imbalance and biceps femoris long head (BFlh) fascicle length on the risk of future hamstring strain injury (HSI). Methods Elite soccer players (n=152) from eight different teams participated. Eccentric knee flexor strength during the Nordic hamstring exercise and BFlh fascicle length were assessed at the beginning of preseason. The occurrences of HSIs following this were recorded by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data. Results Twenty seven new HSIs were reported. Eccentric knee flexor strength below 337 N (RR=4.4; 95% CI 1.1 to 17.5) and possessing BFlh fascicles shorter than 10.56 cm (RR=4.1; 95% CI 1.9 to 8.7) significantly increased the risk of a HSI. Multivariate logistic regression revealed significant effects when combinations of age, history of HSI, eccentric knee flexor strength and BFlh fascicle length were explored. From these analyses the likelihood of a future HSI in older athletes or those with a HSI history was reduced if high levels of eccentric knee flexor strength and longer BFlh fascicles were present. Conclusions The presence of short BFlh fascicles and low levels of eccentric knee flexor strength in elite soccer players increases the risk of future HSI. The greater risk of a future HSI in older players or those with a previous HSI is reduced when they have longer BFlh fascicles and high levels of eccentric strength.

Inconsistent use of terminology in whole body vibration exercise research

Whole body vibration exercise (WBV) intensity can be manipulated by altering the frequency of oscillations and/or its magnitude. The inconsistencies and inaccuracies reported within the literature that at times challenge the replication and advancement of whole body vibration exercise research are discussed. Although frequency is regularly reported, inconsistency exists with the definition of vibration amplitude which has been interchangeably used with other terminology by some researchers. Of primary concern is the risk of injury to participants in future research. Researchers using intensities that were incorrectly reported by previous studies may unwittingly expose participants to harmful intensities. For clarity, an argument is put forward for the standardisation of terminology and reporting of whole body exercise parameters.

Biceps femoris long head architecture: A reliability and retrospective injury study

PURPOSE This study aimed (i) to determine the reliability of two-dimensional ultrasonography for the assessment of biceps femoris long head (BFlh) architectural characteristics and (ii) to determine whether limbs with a history of strain injury in the BFlh display different architecture and eccentric strength compared to uninjured limbs. METHODS This case-control study (control [n = 20], injured group [n = 16], males) assessed the BFlh architecture at rest and during graded isometric contractions using two-dimensional ultrasonography. The control group were assessed three times (>24 h apart) to determine reliability. Previously injured individuals were evaluated once. RESULTS The assessment of BFlh architecture was highly reliable (intraclass correlations >0.90). Fascicle length (P < 0.001; d range = 0.67-1.34) and fascicle length relative to muscle thickness (P < 0.001; d range = 0.58-0.85) of the previously injured BFlh were significantly less than the contralateral uninjured BFlh at all intensities. Pennation angle of the previously injured BFlh was significantly greater (P < 0.001; d range = 0.62-0.88) than the contralateral uninjured BFlh at all intensities. Eccentric strength in the previously injured limb was significantly lower than that in the contralateral limb (-15.4%; -52.5 N, 95% confidence interval = -76.2 to -28.4; P < 0.001, d = 0.56). CONCLUSIONS These data indicate that two-dimensional ultrasonography is reliable for assessing BFlh architecture at rest and during graded isometric contractions. Fascicle length, fascicle length relative to muscle thickness, and pennation angle are significantly different in previously injured BFlh compared to an uninjured contralateral BFlh. Eccentric strength of the previously injured limb is also significantly lower than that of the uninjured contralateral limb. These findings have implications for rehabilitation and injury prevention practices, which should consider altered architectural characteristics.

Efficacy of a Whole-Body Vibration Intervention on Functional Performance of Community-Dwelling Older Adults

OBJECTIVE The objective of this study was to investigate efficacy of a whole-body vibration (WBV) intervention on functional performance of community-dwelling older adults. DESIGN The study was designed as a randomized controlled trial. SETTING The setting was in community centers. SUBJECTS There were 37 total subjects (21 women and 16 men) (age 69 +/- 8 years; mean +/- standard deviation). INTERVENTION Participants were randomized to a WBV intervention (INT) group and control (CON) group. Whole-body vibration was administered for five 1-minute bouts per session, 3 days per week, for 6 weeks. The CON group was asked not to commence any form of physical training. OUTCOME MEASURES Functional performance was measured with the timed-up-and-go-test (TUG) and sit-to-stand-test (STS). RESULTS After WBV, TUG and STS time was less for INT than CON (INT, TUG 7.6 +/- 0.3 seconds, STS 11.9 +/- 2.0 seconds; CON, TUG 8.6 +/- 0.9, STS 13.5 +/- 1.1 seconds; p < 0.05). Within INT, TUG improved 0.9 +/- 0.4 seconds; p = 0.01 and STS improved 3.0 +/- 0.9 seconds; p = 0.05). CONCLUSIONS The efficacy of this WBV intervention was established. Functional performance improvement after WBV may be attributed to a number of biological mechanisms that remain speculative. Further research is required to mechanistically understand the effects of WBV on older adults.

Relationship Between Tests of Physical Qualities and Physical Match Performance in Elite Rugby League Players

Abstract Gabbett, TJ, Stein, JG, Kemp, JG, and Lorenzen, C. Relationship between tests of physical qualities and physical match performance in elite rugby league players. J Strength Cond Res 27(6): 1539–1545, 2013—Previous investigators have reported significant relationships between tests of physical qualities and physical match performance in high-intensity, intermittent team sport (e.g., soccer) players. Although rugby league requires competitors to perform high-intensity running, unlike most other high-intensity intermittent team sports, the physical demands are significantly increased through the large amounts of tackling, wrestling, and grappling that players are required to perform during match play. This study investigated the relationship between tests of physical qualities and match performance in professional rugby league players and determined whether running capacities were associated with the collision and repeated high-intensity effort demands of match play. Thirty-eight elite rugby league players (mean ± SD, age, 23.1 ± 2.7 years) performed tests of repeated sprint ability (12 × 20-m sprints on a 20-second cycle), prolonged high-intensity intermittent running ability (8 × 12-second shuttle sprints on a 48-second cycle), and estimated maximal aerobic power (V[Combining Dot Above]O2max) (multistage fitness test). Global positioning system data were collected during 16 professional rugby league matches. Players with better, prolonged, high-intensity intermittent running ability covered greater total distance and greater distance in high-speed running during match play. However, inconsistent relationships were found between tests of running abilities and other match performance variables, with prolonged high-intensity running ability (negative), V[Combining Dot Above]O2max (positive), and repeated-sprint ability (no relationship) differentially associated with the total number of collisions and repeated high-intensity effort bouts performed in competition. These findings demonstrate the importance of prolonged high-intensity running ability to the match running performance of elite rugby league players but also highlight the need for game-specific conditioning to prepare players for the high-intensity collision and repeated-effort demands of the game.

Characteristics impacting on session rating of perceived exertion training load in Australian footballers.

Abstract The relationship between external training load and session rating of perceived exertion (s-RPE) training load and the impact that playing experience, playing position and 2-km time-trial performance had on s-RPE training load were explored. From 39 Australian Football players, 6.9 ± 4.6 training sessions were analysed, resulting in 270 samples. Microtechnology devices provided external training load (distance, average speed, high-speed running distance, player load (PL) and player loadslow (PLslow)). The external training load measures had moderate to very large associations (r, 95% CI) with s-RPE training load, average speed (0.45, 0.35–0.54), high-speed running distance (0.51, 0.42–0.59), PLslow (0.80, 0.75–0.84), PL (0.86, 0.83–0.89) and distance (0.88, 0.85–0.90). Differences were described using effect sizes (d ±95% CL). When controlling for external training load, the 4- to 5-year players had higher s-RPE training load than the 0- to 1- (0.44 ± 0.33) and 2- to 3-year players (0.51 ± 0.30), ruckmen had moderately higher s-RPE training load than midfielders (0.82 ± 0.58), and there was a 0.2% increase in s-RPE training load per 1 s increase in time-trial (95% CI: 0.07–0.34). Experience, position and time-trial performance impacted the relationship between external training load and s-RPE training load. This suggests that a given external training load may result in different internal responses between athletes, potentially leaving individuals at risk of overtraining or failing to elicit positive adaptation. It is therefore vital that coaches and trainers give consideration to these mediators of s-RPE training load.

Acute Hyperglycemia Impairs Vascular Function in Healthy and Cardiometabolic Diseased Subjects Systematic Review and Meta-Analysis

Objectives—Controversy exists over the effect of acute hyperglycemia on vascular function. In this systematic review, we compared the effect of acute hyperglycemia on endothelial and vascular smooth muscle functions across healthy and cardiometabolic diseased subjects. Approach and Results—A systematic search of MEDLINE, EMBASE, and Web of Science from inception until July 2014 identified articles evaluating endothelial or vascular smooth muscle function during acute hyperglycemia and normoglycemia. Meta-analyses compared the standardized mean difference (SMD) in endothelial and vascular smooth muscle functions between acute hyperglycemia and normoglycemia. Subgroup analyses and metaregression identified sources of heterogeneity. Thirty-nine articles (525 healthy and 540 cardiometabolic subjects) were analyzed. Endothelial function was decreased (39 studies; n=1065; SMD, −1.25; 95% confidence interval, −1.52 to −0.98; P<0.01), whereas vascular smooth muscle function was preserved (6 studies; n=144; SMD, −0.07; 95% confidence interval, −0.30 to 0.16; P=0.55) during acute hyperglycemia compared with normoglycemia. Significant heterogeneity was detected among endothelial function studies (P<0.01). A subgroup analysis revealed that endothelial function was decreased in the macrocirculation (30 studies; n=884; SMD, −1.40; 95% confidence interval, −1.68 to −1.12; P<0.01) but not in the microcirculation (9 studies; n=181; SMD, −0.63; 95% confidence interval, −1.36 to 0.11; P=0.09). Similar results were observed according to health status. Macrovascular endothelial function was inversely associated with age, blood pressure, and low-density lipoprotein cholesterol and was positively associated with the postocclusion interval of vascular assessment. Conclusions—To our knowledge, this is the first systematic review and meta-analysis of its kind. In healthy and diseased subjects, we found evidence for macrovascular but not microvascular endothelial dysfunction during acute hyperglycemia.

Endurance and sprint benefits of high-intensity and supramaximal interval training

Abstract This study examined the effect of two different interval training programs–high-intensity interval training (HIT) and supramaximal interval training (SMIT)–on measures of sprint and endurance performance. Physically active individuals (Females: n=32; age 19.3, s=2.2 years; mass 67.6, s=9.1 kg; stature 172.7, s=6.6 cm. Males: n=23; age 20.0, s=2.7 years; mass 71.3, s=8.3 kg; stature 176.6, s=5.8 cm) completed pre-testing that comprised (1) 3000 m time-trial, (2) 40 m sprint, and (3) repeated sprint ability (RSA–6×40 m sprints, 24 s active recovery) performance. Participants were then matched for average 3000 m running velocity (AV) and randomly assigned to one of three groups: (i) HIT, n=19, 4 min at 100% AV, 4 min passive recovery, 4–6 bouts per session; (ii) SMIT, n=20, 30 s at 130% AV, 150 s passive recovery, 7–12 bouts per session; and (iii) control group, n=16, 30 min continuous running at 75% AV. Groups trained three times per week for six weeks. When time to complete each test were compared among groups: (i) improvements in 3000 m time trial performance were greater following SMIT than continuous running, and (ii) improvements in 40 m sprint and RSA performance were greater following SMIT than HIT and continuous running. In addition, a gender effect was observed for the 3000 m time trial only, where females changed more following the training intervention than males. In summary, for concurrent improvements in endurance, sprint and repeated sprint performance, SMIT provides the greatest benefits for physically active individuals.

Benefits of whole-body vibration to people with COPD: a community-based efficacy trial

BackgroundBenefits of community-based whole-body vibration (WBV) as a mode of exercise training for people with chronic obstructive pulmonary disease (COPD) have not been investigated. The low skill demand of WBV may enhance habitual sustainability to physical activity by people with COPD, provided efficacy of WBV can be established. The purpose of this trial was to compare a community-based WBV intervention with a sham WBV (SWBV) intervention and monitor exacerbations, exercise tolerance, and functional performance of the lower limbs of people with COPD.MethodsCommunity-dwelling adults with a GOLD clinical diagnosis of COPD were recruited to the trial. This was a Phase II efficacy trial with crossover to sham intervention interspersed with two-week washout. Each six-week intervention consisted of two sessions per week of either WBV or SWBV. The interventions were completed in the home of each participant under supervision. The outcome measures were selected psychological (perceived dyspnoea) and physiological (heart rate and oxygen saturation) responses to exercise, simulated activities of daily living (timed-up-and got test and 5-chair stands test), and selected kinematic variables of gait across the 14-week trial.ResultsSixteen adults with stable COPD were recruited to the trial. No exacerbations were reported during the WBV or SWBV interventions. After WBV, performance of activities of daily living (ADLs) and gait improved (p ≤ 0.05), while there was no change after SWBV (p > 0.05). Despite five withdrawals during the washout period, a 100% compliance to each six-week intervention was noted.ConclusionsResults showed that WBV did not exacerbate symptoms of COPD that can be associated with physical inactivity. The WBV intervention improved tests to simulate ADLs such as rising from a chair, turning, and walking gait with greater effect than a SWBV intervention. If a placebo effect was systemic to the WBV intervention, the effect was negligible. As a standalone community-based intervention, WBV was an efficacious mode of exercise training for people with stable COPD that did not negatively effect exercise tolerance or exacerbate the disease, while concurrently improving functional performance of the lower limbs.Trial registrationAustralian and New Zealand Clinical Trials Registry ACTRN12612000508875.

Pre-training perceived wellness impacts training output in Australian football players.

ABSTRACT The impact of perceived wellness on a range of external load parameters, rating of perceived exertion (RPE) and external load:RPE ratios, was explored during skill-based training in Australian footballers. Fifteen training sessions involving 36 participants were analysed. Each morning before any physical training, players completed a customised perceived wellness questionnaire (sleep quality, fatigue, stress, mood and muscle soreness). Microtechnology devices provided external load (average speed, high-speed running distance, player load and player load slow). Players provided RPE using the modified Borg category-ratio 10 RPE scale. Mixed-effect linear models revealed significant effects of wellness Z-score on player load and player load slow. Effects are reported with 95% confidence limits. A wellness Z-score of −1 corresponded to a −4.9 ± 3.1 and −8.6 ± 3.9% reduction in player load and player load slow, respectively, compared to those without reduced wellness. Small significant effects were also seen in the average speed:RPE and player load slow:RPE models. A wellness Z-score of −1 corresponded to a 0.43 ± 0.38 m·min−1 and −0.02 ± 0.01 au·min−1 change in the average speed:RPE and player load slow:RPE ratios, respectively. Magnitude-based analysis revealed that the practical size of the effect of a pre-training perceived wellness Z-score of −1 would have on player load slow was likely negative. The results of this study suggests that monitoring pre-training perceived wellness may provide coaches with information about the intensity of output that can be expected from individual players during a training session.