Evolution of 1500-m Olympic Running Performance.

PURPOSE: This study determined the evolution of performance and pacing for each winner of the men's Olympic 1500-m running track final from 1924 to 2020. METHODS: Data were obtained from publicly available sources. When official splits were unavailable, times from sources such as YouTube were included and interpolated from video records. Final times, lap splits, and position in the peloton were included. The data are presented relative to 0 to 400 m, 400 to 800 m, 800 to 1200 m, and 1200 to 1500 m. Critical speed and D' were calculated using athletes' season's best times. RESULTS: Performance improved ∼25 seconds from 1924 to 2020, with most improvement (∼19 s) occurring in the first 10 finals. However, only 2 performances were world records, and only one runner won the event twice. Pacing evolved from a fast start-slow middle-fast finish pattern (reverse J-shaped) to a slower start with steady acceleration in the second half (J-shaped). The coefficient of variation for lap speeds ranged from 1.4% to 15.3%, consistent with a highly tactical pacing pattern. With few exceptions, the eventual winners were near the front throughout, although rarely in the leading position. There is evidence of a general increase in both critical speed and D' that parallels performance. CONCLUSIONS: An evolution in the pacing pattern occurred across several "eras" in the history of Olympic 1500-m racing, consistent with better trained athletes and improved technology. There has been a consistent tactical approach of following opponents until the latter stages, and athletes should develop tactical flexibility, related to their critical speed and D', in planning prerace strategy.

Nucleus reticularis tegmenti pontis: a bridge between the basal ganglia and cerebellum for movement control.

Neural processing in the basal ganglia is critical for normal movement. Diseases of the basal ganglia, such as Parkinson's disease, produce a variety of movement disorders including akinesia and bradykinesia. Many believe that the basal ganglia influence movement via thalamic projections to motor areas of the cerebral cortex and through projections to the cerebellum, which also projects to the motor cortex via the thalamus. However, lesions that interrupt these thalamic pathways to the cortex have little effect on many movements, including limb movements. Yet, limb movements are severely impaired by basal ganglia disease or damage to the cerebellum. We can explain this impairment as well as the mild effects of thalamic lesions if basal ganglia and cerebellar output reach brainstem motor regions without passing through the thalamus. In this report, we describe several brainstem pathways that connect basal ganglia output to the cerebellum via nucleus reticularis tegmenti pontis (NRTP). Additionally, we propose that widespread afferent and efferent connections of NRTP with the cerebellum could integrate processing across cerebellar regions. The basal ganglia could then alter movements via descending projections of the cerebellum. Pathways through NRTP are important for the control of normal movement and may underlie deficits associated with basal ganglia disease.

Competition Between Desired Competitive Result, Tolerable Homeostatic Disturbance, and Psychophysiological Interpretation Determines Pacing Strategy.

Scientific interest in pacing goes back >100 years. Contemporary interest, both as a feature of athletic competition and as a window into understanding fatigue, goes back >30 years. Pacing represents the pattern of energy use designed to produce a competitive result while managing fatigue of different origins. Pacing has been studied both against the clock and during head-to-head competition. Several models have been used to explain pacing, including the teleoanticipation model, the central governor model, the anticipatory-feedback-rating of perceived exertion model, the concept of a learned template, the affordance concept, the integrative governor theory, and as an explanation for "falling behind." Early studies, mostly using time-trial exercise, focused on the need to manage homeostatic disturbance. More recent studies, based on head-to-head competition, have focused on an improved understanding of how psychophysiology, beyond the gestalt concept of rating of perceived exertion, can be understood as a mediator of pacing and as an explanation for falling behind. More recent approaches to pacing have focused on the elements of decision making during sport and have expanded the role of psychophysiological responses including sensory-discriminatory, affective-motivational, and cognitive-evaluative dimensions. These approaches have expanded the understanding of variations in pacing, particularly during head-to-head competition.

Design guidance for video chat system to support social engagement for older adults with and without mild cognitive impairment.

Background: Social engagement technologies offer an opportunity to reduce social isolation. However, there are barriers to adoption among older adults with and without Mild Cognitive Impairment (MCI). Technology designed to meet the needs of those users may improve the acceptability, adoption, and benefits of social engagement technology. Objective: The goal was to assess older adults' needs and preferences for using video chat systems. We used the Technology Acceptance Model as a framework for evaluating and optimizing usability of a web-based video chat system for older adults with and without MCI. Methods: Mixed methods (qualitative and quantitative) were used to achieve this objective. We developed questionnaires and interviews to identify experiences with video chat, and preferences and attitudes towards a web-based video chat system. We conducted heuristic analysis to evaluate and improve the usability of the system. Results: Participants reportedly used video chat less than other social network tools (e.g., Email). They were open to using a web-based video chat system to meet new people of all ages with shared interests. Their favorite topics of conversation were books, health, family, and exercise. Their ideal group size for a video chat session was 3 to 6 people. Overall, participants' attitudes toward the system were positive and they perceived the system as easy to use and useful for social engagement. Their evaluations indicated high usability of the system. However, individuals with MCI might require additional assistance to use the system. Usability issues were identified, such as technical terminology, small font size, and potentially confusing icons that were addressed in the redesign. Conclusion: Older adults, with and without MCI, were interested in using a social engagement technology to interact with previously unfamiliar individuals with shared interests. They provided valuable insights for the design of the systems. Our findings provide guidance for the design of social engagement technologies. Our research approach serves as a case study for the assessment of other technology platforms.

Caffeine and Placebo Improved Maximal Exercise Performance Despite Unchanged Motor Cortex Activation and Greater Prefrontal Cortex Deoxygenation.

Caffeine (CAF) is an ergogenic aid used to improve exercise performance. Independent studies have suggested that caffeine may have the ability to increase corticospinal excitability, thereby decreasing the motor cortex activation required to generate a similar motor output. However, CAF has also been suggested to induce a prefrontal cortex (PFC) deoxygenation. Others have suggested that placebo (PLA) may trigger comparable effects to CAF, as independent studies found PLA effects on motor performance, corticospinal excitability, and PFC oxygenation. Thus, we investigated if CAF and CAF-perceived PLA may improve motor performance, despite the likely unchanged MC activation and greater PFC deoxygenation. Nine participants (26.4 ± 4.8 years old, VO2MAX of 42.2 ± 4.6 mL kg-1 min-1) performed three maximal incremental tests (MITs) in control (no supplementation) and ∼60 min after CAF and PLA ingestion. PFC oxygenation (near-infrared spectroscopy at Fp1 position), MC activation (EEG at Cz position) and vastus lateralis and rectus femoris muscle activity (EMG) were measured throughout the tests. Compared to control, CAF and PLA increased rectus femoris muscle EMG (P = 0.030; F = 2.88; d = 0.84) at 100% of the MIT, and enhanced the peak power output (P = 0.006; F = 12.97; d = 1.8) and time to exhaustion (P = 0.007; F = 12.97; d = 1.8). In contrast, CAF and PLA did not change MC activation, but increased the PFC deoxygenation as indicated by the lower O2Hb (P = 0.001; F = 4.68; d = 1.08) and THb concentrations (P = 0.01; F = 1.96; d = 0.7) at 80 and 100% the MIT duration. These results showed that CAF and CAF-perceived PLA had the ability to improve motor performance, despite unchanged MC activation and greater PFC deoxygenation. The effectiveness of CAF as ergogenic aid to improve MIT performance was challenged.

Exploring the performance reserve: Effect of different magnitudes of power output deception on 4,000 m cycling time-trial performance.

PURPOSE: The aim of the present study was to investigate whether a magnitude of deception of 5% in power output would lead to a greater reduction in the amount of time taken for participants to complete a 4000 m cycling TT than a magnitude of deception of 2% in power output, which we have previously shown can lead to a small change in 4000 m cycling TT performance. METHODS: Ten trained male cyclists completed four, 4000 m cycling TTs. The first served as a habituation and the second as a baseline for future trials. During trials three and four participants raced against a pacer which was set, in a randomized order, at a mean power output equal to 2% (+2% TT) or 5% (+5% TT) higher than their baseline performance. However participants were misled into believing that the power output of the pacer was an accurate representation of their baseline performance on both occasions. Cardiorespiratory responses were recorded throughout each TT, and used to estimate energy contribution from aerobic and anaerobic metabolism. RESULTS: Participants were able to finish the +2% TT in a significantly shorter duration than at baseline (p = 0.01), with the difference in performance likely attributable to a greater anaerobic contribution to total power output (p = 0.06). There was no difference in performance between the +5% TT and +2% TT or baseline trials. CONCLUSIONS: Results suggest that a performance reserve is conserved, involving anaerobic energy contribution, which can be utilised given a belief that the exercise will be sustainable however there is an upper limit to how much deception can be tolerated. These findings have implications for performance enhancement in athletes and for our understanding of the nature of fatigue during high-intensity exercise.

Cerebral Regulation in Different Maximal Aerobic Exercise Modes.

We investigated cerebral responses, simultaneously with peripheral and ratings of perceived exertion (RPE) responses, during different VO2MAX-matched aerobic exercise modes. Nine cyclists (VO2MAX of 57.5 ± 6.2 ml·kg(-1)·min(-1)) performed a maximal, controlled-pace incremental test (MIT) and a self-paced 4 km time trial (TT4km). Measures of cerebral (COX) and muscular (MOX) oxygenation were assessed throughout the exercises by changes in oxy- (O2Hb) and deoxy-hemoglobin (HHb) concentrations over the prefrontal cortex (PFC) and vastus lateralis (VL) muscle, respectively. Primary motor cortex (PMC) electroencephalography (EEG), VL, and rectus femoris EMG were also assessed throughout the trials, together with power output and cardiopulmonary responses. The RPE was obtained at regular intervals. Similar motor output (EMG and power output) occurred from 70% of the duration in MIT and TT4km, despite the greater motor output, muscle deoxygenation (↓ MOX) and cardiopulmonary responses in TT4km before that point. Regarding cerebral responses, there was a lower COX (↓ O2Hb concentrations in PFC) at 20, 30, 40, 50 and 60%, but greater at 100% of the TT4km duration when compared to MIT. The alpha wave EEG in PMC remained constant throughout the exercise modes, with greater values in TT4km. The RPE was maximal at the endpoint in both exercises, but it increased slower in TT4km than in MIT. Results showed that similar motor output and effort tolerance were attained at the closing stages of different VO2MAX-matched aerobic exercises, although the different disturbance until that point. Regardless of different COX responses during most of the exercises duration, activation in PMC was preserved throughout the exercises, suggesting that these responses may be part of a centrally-coordinated exercise regulation.

Asymmetry of Cerebral Hemodynamic Response to Incremental Cycling Exercise.

PURPOSE: Exercise is known to result in hemodynamic changes in the bilateral prefrontal cortex. The aim of this study was to investigate hemodynamic changes in right and left hemispheres of the prefrontal cortex (PFC) during incremental cycling exercise. METHODS: After 10 min rest, 9 participants (mean age 26.6 ± 2.5 y, mass 77.5 ± 9.7 kg, stature 1.79 ± 0.9 m) cycled at 100-150 W for 4 min. Thereafter, resistance was increased by 25 W every 4 min until exhaustion (EXH). Respiratory exchange and concentrations of oxy- ([HbO2]), deoxy- ([(HHb]), and total hemoglobin ([Hb(tot)]) in the PFC were continuously measured. Data were averaged for 60 s at rest and preceding ventilatory threshold 1 (VT1), VT2, and volitional EXH and after 5 min recovery. Subjective ratings of affect were measured at VT1, VT2, VT1 minus 25 W (VT1-25W), and VT2 plus 25 W (VT2+25W). RESULTS: There were no between-hemispheres differences in [HbO2] or [Hb(tot)] at rest, VT1, or recovery or in [HHb] at any point. Right-hemisphere [HbO2] and [Hb(tot)] were significantly greater than left at VT2 (P = .01 and P = .02) and EXH (P = .03 and P = .02). Affect was significantly greater at VT1-25W vs VT2 and VT2+25W and at VT1 and VT2 vs VT2+25W (P < .01-.03). CONCLUSIONS: To the authors' knowledge, this is the first study to describe an exercise-state-dependent change in PFC asymmetry during incremental exercise. The asymmetry detected coincided with a decrease in affect scores in agreement with the PFC-asymmetry hypothesis.

Neuromuscular changes associated with superior fatigue resistance in African runners.

BACKGROUND: An enhanced ability to resist fatigue has been proposed as one of African runners' performance superiority sources, although their fatigue resistance during sustained non-running-specific activities remain unclear. This study aimed to compare fatigue resistance during sustained isometric exercise between performance-matched African and European runners. METHODS: Thirty long-distance runners (16 African, 14 European) performed submaximal fatiguing sustained isometric knee extensions. Rectus femoris electromyographic (EMG) activity was measured, and the muscle was electrically stimulated to contract at the beginning and end of the test. RESULTS: Time to task failure was greater for African than European runners (269±115 vs. 193±52 s, P=0.002; effect size [ES]=0.85, large effect). During the test, EMG amplitude increased less over time (P=0.031), and the left shift in the EMG frequency spectrum was less over time for the African runners (P<0.001). In addition, there was a lower relative reduction in stimulated force output from the first to the second stimulation in African runners (17.75±14.95 vs. 37.89±14.78%, P=0.006; ES=1.35; large effect). CONCLUSIONS: These findings of greater fatigue resistance during non-running-specific activity and the associated muscle recruitment profile may contribute to the understanding of the physiology underlying endurance performance in African runners.

Signaling Responses After Varying Sequencing of Strength and Endurance Training in a Fed State.

PURPOSE: To compare anabolic signaling responses to differing sequences of concurrent strength and endurance training in a fed state. METHODS: Eighteen resistance-trained men were randomly assigned to the following experimental conditions: strength training (ST), strength followed by endurance training (ST-END), or endurance followed by strength training (END-ST). Muscle tissue samples were taken from the vastus lateralis before each exercise protocol, on cessation of exercise, and 1 h after cessation of strength training. Tissue was analyzed for total and phosphorylated (p-) signaling proteins linked to the mTOR and AMPK networks. RESULTS: Strength-training performance was similar between ST, ST-END, and END-ST. p-S6k1 was elevated from baseline 1 h posttraining in ST and ST-END (both P < .05). p-4E-BP1 was significantly lower than baseline post-ST (P = .01), whereas at 1 h postexercise in the ST-END condition p-4E-BP1 was significantly greater than postexercise (P = .04). p-ACC was elevated from baseline both postexercise and 1 h postexercise (both P < .05) in the END-ST condition. AMPK, mTOR, p38, PKB, and eEF2 responded similarly to ST, ST-END, and END-ST. Signaling responses to ST, ST-END, and END were largely similar. As such it cannot be ascertained which sequence of concurrent strength and endurance training is most favorable in promoting anabolic signaling. CONCLUSIONS: In the case of the current study an acute bout of concurrent training of differing sequences elicited similar responses of the AMPK and mTOR networks.

Increased variability of lap speeds: differentiating medalists and nonmedalists in middle-distance running and swimming events.

PURPOSE: Previous literature has presented pacing data of groups of competition finalists. The aim of this study was to analyze the pacing patterns displayed by medalists and nonmedalists in international competitive 400-m swimming and 1500-m running finals. METHODS: Split times were collected from 48 swimming finalists (four 100-m laps) and 60 running finalists (4 laps) in international competitions from 2004 to 2012. Using a cross-sectional design, lap speeds were normalized to whole-race speed and compared to identify variations of pace between groups of medalists and nonmedalists. Lap-speed variations relative to the gold medalist were compared for the whole field. RESULTS: In 400-m swimming the medalist group demonstrated greater variation in speed than the nonmedalist group, being relatively faster in the final lap (P < .001; moderate effect) and slower in laps 1 (P = .03; moderate effect) and 2 (P > .001; moderate effect). There were also greater variations of pace in the 1500-m running medalist group than in the nonmedalist group, with a relatively faster final lap (P = .03; moderate effect) and slower second lap (P = .01; small effect). Swimming gold medalists were relatively faster than all other finalists in lap 4 (P = .04), and running gold medalists were relatively faster than the 5th- to 12th-placed athletes in the final lap (P = .02). CONCLUSIONS: Athletes who win medals in 1500-m running and 400-m swimming competitions show different pacing patterns than nonmedalists. End-spurt-speed increases are greater with medalists, who demonstrate a slower relative speed in the early part of races but a faster speed during the final part of races than nonmedalists.

Risk perception influences athletic pacing strategy.

PURPOSE: The objective of this study is to examine risk taking and risk perception associations with perceived exertion, pacing, and performance in athletes. METHODS: Two experiments were conducted in which risk perception was assessed using the domain-specific risk taking (DOSPERT) scale in 20 novice cyclists (experiment 1) and 32 experienced ultramarathon runners (experiment 2). In experiment 1, participants predicted their pace and then performed a 5-km maximum effort cycling time trial on a calibrated Kingcycle mounted bicycle. Split times and perceived exertion were recorded every kilometer. In experiment 2, each participant predicted their split times before running a 100-km ultramarathon. Split times and perceived exertion were recorded at seven checkpoints. In both experiments, higher and lower risk perception groups were created using median split of DOSPERT scores. RESULTS: In experiment 1, pace during the first kilometer was faster among lower risk perceivers compared with higher risk perceivers (t(18) = 2.0, P = 0.03) and faster among higher risk takers compared with lower risk takers (t(18) = 2.2, P = 0.02). Actual pace was slower than predicted pace during the first kilometer in both the higher risk perceivers (t(9) = -4.2, P = 0.001) and lower risk perceivers (t(9) = -1.8, P = 0.049). In experiment 2, pace during the first 36 km was faster among lower risk perceivers compared with higher risk perceivers (t(16) = 2.0, P = 0.03). Irrespective of risk perception group, actual pace was slower than predicted pace during the first 18 km (t(16) = 8.9, P < 0.001) and from 18 to 36 km (t(16) = 4.0, P < 0.001). In both experiments, there was no difference in performance between higher and lower risk perception groups. CONCLUSIONS: Initial pace is associated with an individual's perception of risk, with low perceptions of risk being associated with a faster starting pace. Large differences between predicted and actual pace suggest that the performance template lacks accuracy, perhaps indicating greater reliance on momentary pacing decisions rather than preplanned strategy.

Effects of 1 week of unilateral ankle immobilization on plantar-flexor strength, balance, and walking speed: a pilot study in asymptomatic volunteers.

CONTEXT: Ankle immobilization is often used after ankle injury. OBJECTIVE: To determine the influence of 1 week's unilateral ankle immobilization on plantar-flexor strength, balance, and walking gait in asymptomatic volunteers. DESIGN: Repeated-measures laboratory study. SETTING: University laboratory. PARTICIPANTS: 6 physically active male participants with no recent history of lower-limb injury. INTERVENTIONS: Participants completed a 1-wk period of ankle immobilization achieved through wearing a below-knee ankle cast. Before the cast was applied, as well as immediately, 24 h, and 48 h after cast removal, their plantar-flexor strength was assessed isokinetically, and they completed a single-leg balance task as a measure of proprioceptive function. An analysis of their walking gait was also completed Main Outcome Measures: Peak plantar-flexor torque and balance were used to determine any effect on muscle strength and proprioception after cast removal. Ranges of motion (3D) of the ankle, knee, and hip, as well as walking speed, were used to assess any influence on walking gait. RESULTS: After cast removal, plantar-flexor strength was reduced for the majority of participants (P = .063, CI = -33.98 to 1.31) and balance performance was reduced in the immobilized limb (P < .05, CI = 0.84-5.16). Both strength and balance were not significantly different from baseline levels by 48 h. Walking speed was not significantly different immediately after cast removal but increased progressively above baseline walking speed over the following 48 h. Joint ranges of motion were not significantly different at any time point. CONCLUSIONS: The reduction in strength and balance after such a short period of immobilization suggested compromised central and peripheral neural mechanisms. This suggestion appeared consistent with the delayed increase in walking speed that could occur as a result of the excitability of the neural pathways increasing toward baseline levels.

Central and peripheral fatigue in male cyclists after 4-, 20-, and 40-km time trials.

PURPOSE: Few studies have assessed neuromuscular fatigue after self-paced locomotor exercise; moreover, none have assessed the degree of supraspinal fatigue. This study assessed central and peripheral fatigue after self-paced exercise of different durations. METHODS: Thirteen well-trained male cyclists completed 4-, 20-, and 40-km simulated time trials (TTs). Pre- and immediately post-TT (<2.5 min), twitch responses from the knee extensors to electrical stimulation of the femoral nerve and transcranial magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function. RESULTS: Time to complete 4-, 20-, and 40-km TTs was 6.0 ± 0.2, 31.8 ± 1.0, and 65.8 ± 2.2 min at average exercise intensities of 96%, 92%, and 87% of maximum oxygen uptake, respectively. Exercise resulted in significant reductions in maximum voluntary contraction, with no difference between TTs (-18%, -15%, and -16% for 4-, 20-, and 40-km TTs, respectively). Greater peripheral fatigue was evident after 4-km (40% reduction in potentiated twitch) compared with that after 20-km (31%) and 40-km TTs (29%). In contrast, longer TTs were characterized by more central fatigue, with greater reductions in voluntary activation measured by motor nerve (-11% and -10% for 20- and 40-km TTs vs -7% for 4-km TTs) and cortical stimulation (-12% and -10% for 20- and 40-km vs -6% for 4-km). CONCLUSIONS: These data demonstrate that fatigue after self-paced exercise is task dependent, with a greater degree of peripheral fatigue after shorter higher-intensity (6 min) TTs and more central fatigue after longer lower-intensity TTs (>30 min).

Psychophysiological responses in experienced firefighters undertaking repeated self-contained breathing apparatus tasks.

In order to safely and effectively extinguish fires and rescue life, firefighters are required to routinely wear self-contained breathing apparatus (SCBA), yet little is known about the specific physiological and psychological demands associated with repeated exposure to tasks that require SCBA. A total of 12 experienced firefighters took part in a series of commonly encountered SCBA activities: free search, guideline search and live firefighting tasks under room temperature (∼20°C) and extreme heat (∼180°C) conditions to assess changes in heart rate, blood pressure, mood, perceived workload and air usage. Findings demonstrate that live firefighting is associated with greater perceived exhaustion than free search or guideline exercises; however, all tasks lead to high cardiovascular demand regardless of the presence of heat. No significant impact of task upon mood and no significant differences between the perceived demands of guideline, free search and live firefighting exercises were found.

Stressors and coping strategies of U.K. firefighters during on-duty incidents.

Operational response by firefighters requires an abrupt change from rest to near-maximal physical effort and incorporates almost instant stress management that must be made during extreme heat, limited time and partial information, yet little is known about the coping strategies incorporated to manage the physiological and psychological demands associated with this environment. A sample of 22 UK firefighters took part in focus groups identifying frequently used coping techniques based upon problem-focused and emotion-focused coping methods. Findings suggest problem-orientated coping comprised half of the total coping strategies quoted by participants, with a third of responses being categorized as emotion-focused methods, and 17% were considered to be both problem-focused and emotion-focused techniques. Responses indicate problem-focused methods are often utilized en route to the incident, and at the early stages of operational tasks. Emotion-focused responses are more common during periods of fatigue and exhaustion and post-incident, and problem-focused and emotion-focused techniques were found post-incident, although there was often an overlap between methods and they perhaps should not be treated as three distinct stages. The importance of peer support and potential benefits to firefighter well-being and operational performance are discussed.

Complexity analysis of sleep and alterations with insomnia based on non-invasive techniques.

For the first time, fractal analysis techniques are implemented to study the correlations present in sleep actigraphy for individuals suffering from acute insomnia with comparisons made against healthy subjects. Analysis was carried out for 21 healthy individuals with no diagnosed sleep disorders and 26 subjects diagnosed with acute insomnia during night-time hours. Detrended fluctuation analysis was applied in order to look for 1/f-fluctuations indicative of high complexity. The aim is to investigate whether complexity analysis can differentiate between people who sleep normally and people who suffer from acute insomnia. We hypothesize that the complexity will be higher in subjects who suffer from acute insomnia owing to increased night-time arousals. This hypothesis, although contrary to much of the literature surrounding complexity in physiology, was found to be correct-for our study. The complexity results for nearly all of the subjects fell within a 1/f-range, indicating the presence of underlying control mechanisms. The subjects with acute insomnia displayed significantly higher correlations, confirmed by significance testing-possibly a result of too much activity in the underlying regulatory systems. Moreover, we found a linear relationship between complexity and variability, both of which increased with the onset of insomnia. Complexity analysis is very promising and could prove to be a useful non-invasive identifier for people who suffer from sleep disorders such as insomnia.

Gait analysis of fixed bearing and mobile bearing total knee prostheses during walking: do mobile bearings offer functional advantages?

BACKGROUND: Limited previous findings have detailed biomechanical advantages following implantation with mobile bearing (MB) prostheses after total knee replacement (TKR) surgery during walking. The aim of this study was to compare three dimensional spatiotemporal, kinematic, and kinetic parameters during walking to examine whether MBs offer functional advantages over fixed bearing (FB) designs. METHODS: Sixteen patients undergoing primary unilateral TKR surgery were randomised to receive either a FB (n=8) or MB (n=8) total knee prosthesis. Eight age and gender matched controls underwent the same protocol on one occasion. A 12 camera Vicon system integrated with four force plates was used. Patients were tested pre-surgery and nine months post-surgery. RESULTS: No significant differences between FB and MB groups were found at any time point in the spatiotemporal parameters. The MB group was found to have a significantly reduced frontal plane knee range of motion (ROM) at pre-surgery than the FB group (FB=14.92±4.02°; MB=8.87±4.82°), with the difference not observed post-surgery. No further significant kinematic or kinetic differences were observed between FB and MB groups. Fixed bearing and MB groups both displayed spatiotemporal, kinematic, and kinetic differences when compared to controls. Fixed bearing and MB groups differed from controls in six and five parameters at nine months post-surgery, respectively. CONCLUSIONS: No functional advantages were found in knees implanted with MB prostheses during walking, with both groups indicative of similar differences when compared to normal knee biomechanics following prosthesis implantation. LEVEL OF EVIDENCE: Level II.

Application of decision-making theory to the regulation of muscular work rate during self-paced competitive endurance activity.

Successful participation in competitive endurance activities requires continual regulation of muscular work rate in order to maximise physiological performance capacities, meaning that individuals must make numerous decisions with regards to the muscular work rate selected at any point in time. Decisions relating to the setting of appropriate goals and the overall strategic approach to be utilised are made prior to the commencement of an event, whereas tactical decisions are made during the event itself. This review examines current theories of decision-making in an attempt to explain the manner in which regulation of muscular work is achieved during athletic activity. We describe rational and heuristic theories, and relate these to current models of regulatory processes during self-paced exercise in an attempt to explain observations made in both laboratory and competitive environments. Additionally, we use rational and heuristic theories in an attempt to explain the influence of the presence of direct competitors on the quality of the decisions made during these activities. We hypothesise that although both rational and heuristic models can plausibly explain many observed behaviours in competitive endurance activities, the complexity of the environment in which such activities occur would imply that effective rational decision-making is unlikely. However, at present, many proposed models of the regulatory process share similarities with rational models. We suggest enhanced understanding of the decision-making process during self-paced activities is crucial in order to improve the ability to understand regulation of performance and performance outcomes during athletic activity.