John A Sampson

The acute:chronic workload ratio predicts injury: high chronic workload may decrease injury risk in elite rugby league players

Aim Investigate whether acute workload (1 week total distance) and chronic workload (4-week average acute workload) predict injury in elite rugby league players. Methods Data were collected from 53 elite players over two rugby league seasons. The ‘acute:chronic workload ratio’ was calculated by dividing acute workload by chronic workload. A value of greater than 1 represented an acute workload greater than chronic workload. All workload data were classified into discrete ranges by z-scores. Results Compared with all other ratios, a very-high acute:chronic workload ratio (≥2.11) demonstrated the greatest risk of injury in the current week (16.7% injury risk) and subsequent week (11.8% injury risk). High chronic workload (>16 095 m) combined with a very-high 2-week average acute:chronic workload ratio (≥1.54) was associated with the greatest risk of injury (28.6% injury risk). High chronic workload combined with a moderate workload ratio (1.02–1.18) had a smaller risk of injury than low chronic workload combined with several workload ratios (relative risk range from 0.3 to 0.7×/÷1.4 to 4.4; likelihood range=88–94%, likely). Considering acute and chronic workloads in isolation (ie, not as ratios) did not consistently predict injury risk. Conclusions Higher workloads can have either positive or negative influences on injury risk in elite rugby league players. Specifically, compared with players who have a low chronic workload, players with a high chronic workload are more resistant to injury with moderate-low through moderate-high (0.85–1.35) acute:chronic workload ratios and less resistant to injury when subjected to ‘spikes’ in acute workload, that is, very-high acute:chronic workload ratios ∼1.5.

Low chronic workload and the acute:chronic workload ratio are more predictive of injury than between-match recovery time: a two-season prospective cohort study in elite rugby league players

Background Between-match recovery time, and acute and chronic workloads likely affect subsequent match-injury risk in elite rugby league players. Methods Workloads of 28 players throughout two seasons were calculated during short (<7 days), and long (≥7 days) between-match recovery times. ‘Acute’ workloads (1 week) greater than ‘chronic’ workloads (4-week rolling average acute workload) resulted in acute:chronic workload ratios above 1. Results No difference was found between the match-injury risk of short and long between-match recovery periods (7.5±2.5% vs 6.8±2.5%). When players had a short recovery between matches, high chronic workloads (18.9–22.0 km) were associated with a smaller risk of match injury than chronic workloads <18.9 km (relative risk (RR) range 0.27–0.32 (CI 0.08 to 0.92); likelihood range 90–95%, likely). Players who had shorter recovery and acute:chronic workload ratios ≥1.6, were 3.4–5.8 times likely to sustain a match injury than players with lower acute:chronic workload ratios (RR range 3.41–5.80 (CI 1.17 to 19.2); likelihood range 96–99%, very likely). Acute:chronic workload ratios between 1.2 and 1.6 during short between-match recovery times demonstrated a greater risk of match injury than ratios between 1.0 and 1.2 (RR=2.88 (CI 0.97 to 8.55); likelihood=92%, likely). Conclusions Contrary to the philosophy that high workloads and shorter recovery equate to increased injury risk, our data suggest that high and very-high chronic workloads may protect against match injury following shorter between-match recovery periods. Acute:chronic workload ratios ∼1.5 are associated with a greater risk of match injury than lower acute:chonic workload ratios. Importantly, workloads can be manipulated to decrease the match-injury risk associated with shorter recovery time between matches.

Is repetition failure critical for the development of muscle hypertrophy and strength

This investigation sought to determine the effect of resistance training to failure on functional, structural and neural elbow flexor muscle adaptation. Twenty‐eight males completed a 4‐week familiarization period and were then counterbalanced on the basis of responsiveness across; non‐failure rapid shortening (RS; rapid concentric, 2 s eccentric), non‐failure stretch‐shortening (SSC; rapid concentric, rapid eccentric), and failure control (C, 2 s concentric, 2 s eccentric), for a 12‐week unilateral elbow flexor resistance training regimen, 3 × week using 85% of one repetition maximum (1RM). 1RM, maximal voluntary contraction (MVC), muscle cross‐sectional area (CSA), and muscle activation (EMGRMS) of the agonist, antagonist, and stabilizer muscles were assessed before and after the 12‐week training period. The average number of repetitions per set was significantly lower in RS 4.2 [confidence interval (CI): 4.2, 4.3] and SSC 4.2 (CI: 4.2, 4.3) compared with C 6.1 (CI: 5.8, 6.4). A significant increase in 1RM (30.5%), MVC (13.3%), CSA (11.4%), and agonist EMGRMS (22.1%) was observed; however, no between‐group differences were detected. In contrast, antagonist EMGRMS increased significantly in SSC (40.5%) and C (23.3%), but decreased in RS (13.5%). Similar adaptations across the three resistance training regimen suggest repetition failure is not critical to elicit significant neural and structural changes to skeletal muscle.

Knowledge of bout duration influences pacing strategies during small-sided games.

Abstract This investigation examines pacing during intermittent team sports. Sixteen junior Rugby League players participated in eight different small-sided offside touch games. All games were 24 min, but bout durations differed in continuous (1 × 24 min) or repeated (2 × 12, 3 × 8, 4 × 6, 6 × 4, 8 × 3, 12 × 2 or 24 × 1 min) formats. Repeat bouts were interspersed by 2 min of passive rest, and participants were informed of the bout duration immediately prior to the game. Heart rates, ratings of perceived exertion and data gathered from global positioning system devices were used to investigate the pacing strategies employed within each game. No significant (P > 0.05) between-game differences were observed in total distance; however, during the 1-min bouts, high-speed movement was significantly (P < 0.05) increased, during the first and second quarters of the 24 × 1-min game compared to all other formats (effect size range: 0.75 ± 0.61–1.38 ± 0.47). Furthermore, the rate of decline in high-speed movement over-time was greatest during the 24 × 1-min game with large differences observed between the first and third quarters (effect size: 0.90 ± 0.58). Greater moderate-speed (effect size range: 0.62 ± 0.63–1.56 ± 0.40) and less low-speed (effect size range: 0.69 ± 0.62–1.54 ± 0.40) distances were also observed during the 1-min bouts, yet heart rates were higher during the continuous 1 × 24-min game. Pacing strategies during intermittent activities are influenced by the number and duration of exercise bouts. Practitioners should consider within-game bout durations when prescribing game-based activities to improve aerobic capacity.

Employment Standards for Australian Urban Firefighters: Part 4: Physical Aptitude Tests and Standards.

Objective: Firefighter physical aptitude tests were administered to unskilled subjects and operational firefighters to evaluate the impact that testing bias associated with gender, age, activity-specific skills, or task familiarity may have upon establishing performance thresholds. Methods: These tests were administered in sequence, simulating hazmat incidents, ventilation fan carriage (stairs), motor-vehicle rescues, bushfire incidents, fire attacks, and a firefighter rescue. Participants included two unskilled samples (N = 14 and 22) and 143 firefighters. Results: Firefighter performance was not significantly different from the unskilled subjects. Participants from both genders passed the test, with scores unrelated to performance skill or age; however, familiarization significantly improved performance when the test was repeated. Conclusion: These outcomes confirmed this test to be gender-, age-, and skill-neutral. Familiarization effects could be removed through performing a single, pre-selection trial of the test battery.

Employment Standards for Australian Urban Firefighters: Part 1: The Essential, Physically Demanding Tasks.

Objective: This communication is the first of four describing the development of defensible firefighter-selection tests. The purpose was to identify a subset of essential, physically demanding tasks performed by contemporary urban firefighters. Methods: From existing procedural documentation and job analyses, 11 fire-station visits and interviews with 106 firefighters, and one focus-group meeting, 31 physically demanding tasks were identified and incorporated into a workforce survey. Using this tool, firefighters rated the importance, perceived difficulty, typical task durations, and annual performance frequency of each task. Results: Data from 989 respondents were analyzed, enabling a consolidation of these tasks into a subset of essential activities. Conclusions: These processes yielded a content-valid list of 15 essential, physically demanding tasks covering the full width of duties performed by urban firefighters from Australias largest fire and rescue organization.

Employment Standards for Australian Urban Firefighters: Part 3: The Transition From Criterion Task to Test.

Objective: In this third communication, the processes for converting criterion occupational tasks into bona fide pre-employment selection tests are presented using urban firefighters as the worked example. Methods: A total of 14 individuals participated in potential screening tests that targeted three loaded movement categories: single-sided load carriage (4 tests), dragging loads (2 tests), and overhead pushing and holding objects (5 tests). Results: Seven tests emerged, one performed as an isolated pass/fail barrier test (ladder raise) and six incorporated into a sequential, timed circuit simulating hazmat incidents, ventilation fan carriage (stairs), motor-vehicle rescues, bushfire incidents, fire attacks, and a firefighter rescue. Conclusion: Because three tests provided predicted performance speeds to replicate the oxygen cost of firefighters performing the corresponding occupational simulations, notional performance thresholds could be projected and recommended for the final phase of this research.

The effect of a familiarisation period on subsequent strength gain

Abstract Untrained subjects can display diverse strength gain following an identical period of resistance exercise. In this investigation, 28 untrained males completed 16-weeks of resistance exercise, comprising 4-weeks familiarisation, and 12-weeks of heavy-load (80–85%) activity. High and low responders were identified by the Δ1RM (Δ one repetition maximum) observed following familiarisation (25.1 ± 1.4%, 9.5 ± 1.4%, P < 0.0001) and differences in electromyographic root mean square amplitude (ΔEMGRMS 29.5 ± 8.3%, 2.4 ± 6.0%, P = 0.0140), and habitual and occupational activity patterns were observed between these respective groups. The strength gain (P < 0.0001) observed within high (29.6 ± 1.7%) and low (31.4 ± 2.7%) responding groups was similar during the heavy-load phase, yet ΔEMGRMS increased (P = 0.0048) only in low responders (31.5 ± 9.3%). Retrospectively, differences (P < 0.0001) in baseline 1RM strength of high- (19.7 ± 0.9 kg) and low-responding (15.6 ± 0.7 kg) groups were identified, and a strong negative correlation with Δ1RM after 16-weeks (r 2 = −0.85) was observed. As such, baseline 1RM strength provided a strong predicative measure of strength adaptation. The ΔEMGRMS suggests strength variability within high and low responders may be attributed to neural adaptation. However, differences in habitual endurance and occupational physical activity suggests one should consider screening not only recent resistance training, but also other modes of physical activity during participant recruitment.

Employment standards for Australian urban firefighters. Part 2: The physiological demands and the criterion tasks

Objective: The physiological demands of 15 essential, physically demanding fire-fighting tasks were investigated to identify criterion tasks for bona fide recruit selection. Methods: A total of 51 operational firefighters participated in discrete, field-based occupational simulations, with physiological responses measured throughout. Results: The most stressful tasks were identified and classified according to dominant fitness attributes and movement patterns. Three movement classes (single-sided load carriage [5 tasks], dragging loads [4 tasks], and overhead pushing and holding objects [2 tasks]) and one mandatory strength task emerged. Seven criterion tasks were identified. Load holding and carriage dominated these movement patterns, yet no task accentuated whole-body endurance. Conclusion: Material handling movements from each classification must appear within a physical aptitude (selection) test for it to adequately represent the breadth of tasks performed by Australian urban firefighters.

The effectiveness of basic military training to improve functional lifting strength in new recruits

Abstract Drain, JR, Sampson, JA, Billing, DC, Burley, SD, Linnane, DM, and Groeller, H. The effectiveness of basic military training to improve functional lifting strength in new recruits. J Strength Cond Res 29(11S): S173–S177, 2015—Australian Army recruits are required to meet the incumbent baseline physical employment standards (PES) during basic military training. A box lift and place (BLP) assessment is included in the PES, and it assesses the ability to perform essential muscular strength tasks. Therefore, basic military training must provide sufficient training stimulus to enable recruits to achieve the baseline BLP standard. A study was undertaken to investigate changes in the performance of 1-repetition maximum BLP in male (n = 154; age, 21.4 years) and female (n = 20; age, 23.1 years) recruits over the first 8 weeks of a 12-week basic military training course. Both male and female recruits showed modest improvements (2.2 ± 5.9 kg and 3.0 ± 3.1 kg, respectively; p ⩽ 0.05) in maximal BLP performance, and there were no differences between genders. The female recruits showed greater relative improvements compared with the male recruits (14.7 ± 7.8% vs. 6.5 ± 2.3%). Despite the modest improvements in BLP performance, 70% of female and 100% of male recruits achieved the baseline BLP standard (25 kg) during week 8. The 30% failure rate for female recruits, however, suggests that the basic training program should be improved. A training program that yields greater gains in muscular strength would likely increase female recruit BLP pass rates. Augmented muscular strength would also likely increase the number of recruits capable of achieving higher BLP standards for more physically demanding employment categories. A training program that yields greater improvements in muscular strength may also enable lower entry standards, thereby increasing the recruit pool.