Drone exploration of bat echolocation: A UAV-borne multimicrophone array to study bat echolocation.

Multimicrophone array techniques offer crucial insight into bat echolocation, yet they severely undersample the environments bats operate in as they are limited in geographic placement and mobility. UAVs are excellent candidates to greatly increase the environments in which such arrays can be deployed, but the impact of UAV noise on recording quality and the UAV's behavioral impact on the bats may affect usability. We developed a UAV-borne multimicrophone setup capable of recording bat echolocation across diverse environments. We quantify and mitigate the impact of UAV noise on the recording setup and test the recording capability of the array by recording four common Danish bat species: Pipistrellus pygmaeus, Myotis daubentonii, Eptesicus serotinus, and Nyctalus noctula. The UAV produces substantial noise at ultrasonic frequencies relevant to many bat species. However, suspending the array 30 m below the UAV attenuates the noise to levels below the self-noise of our recording system at 20 kHz and above, and we successfully record and acoustically localize all four bat species. The behavioral impact of the UAV is minimal as all four species approached the array to within 1 m and all emitted recordable feeding buzzes. UAV-borne multimicrophone arrays will allow us to quantify bat echolocation in hitherto unexplored habitats and provide crucial insight into how bats operate their sonar across their entire natural habitat.

Towards best practice in physical and physiological employment standards.

While the scope of the term physical employment standards is wide, the principal focus of this paper is on standards related to physiological evaluation of readiness for work. Common applications of such employment standards for work are in public safety and emergency response occupations (e.g., police, firefighting, military), and there is an ever-present need to maximize the scientific quality of this research. Historically, most of these occupations are male-dominated, which leads to potential sex bias during physical demands analysis and determining performance thresholds. It is often assumed that older workers advance to positions with lower physical demand. However, this is not always true, which raises concerns about the long-term maintenance of physiological readiness. Traditionally, little attention has been paid to the inevitable margin of uncertainty that exists around cut-scores. Establishing confidence intervals around the cut-score can reduce for this uncertainty. It may also be necessary to consider the effects of practise and biological variability on test scores. Most tests of readiness for work are conducted under near perfect conditions, while many emergency responses take place under far more demanding and unpredictable conditions. The potential impact of protective clothing, respiratory protection, load carriage, environmental conditions, nutrition, fatigue, sensory deprivation, and stress should also be considered when evaluating readiness for work. In this paper, we seek to establish uniformity in terminology in this field, identify key areas of concern, provide recommendations to improve both scientific and professional practice, and identify priorities for future research.

The effect of hand cooling during intermittent training of elite swimmers.

BACKGROUND: The aim of this paper was to determine the effects of using intermittent hand cooling during high intensity, intermittent training on thermoregulatory, performance and psychophysical variables in elite level swimmers in a training pool (30.5±0.5 °C). METHODS: Randomized cross-over design. Following a standard warm-up, ten male swimmers (20.3±3.2 years) were instructed to maintain the fastest 100-m time (on average) for an 8 x 100 m freestyle swimming set performed either in a training pool with cooling (TPC) or a training pool with no-cooling (TPNC). Time at 100 m, core temperature (Tc), heart rate (HR), ratings of perceived exertion (RPE), thermal comfort (ThC) and thermal sensation (ThS) were recorded following each repetition. Participants were cooled during the 90 s rest interval between repetitions using the Rapid Thermal Exchange System (RTX) (AVAcore Technologies Inc., Ann Arbor, MI, USA). RESULTS: There was a better performance when comparing 100 m time (1.50±1.98 s faster) for the final repetition in the TPC condition compared to the final repetition in the TPNC condition (P<0.05). There was no significant difference between Tc, HR, RPE, ThC and ThS (P<0.05). CONCLUSIONS: There was a performance benefit in the last set of the training block in the TPC condition that could not be attributed to any of the physiological and psychophysical measures used in the study.

Variability in performance on a work simulation test of physical fitness for firefighters.

The Canadian Forces Firefighter Physical Fitness Maintenance Evaluation (FF PFME) requires firefighters in full fire-protective ensemble, including self-contained breathing apparatus, to correctly complete 10 work-related tasks on a measured and calibrated course. Fitness for duty is inferred from completion time of the course. We hypothesized that completion time may be dependent on pacing strategy and day-to-day fluctuations in biological function. To examine variability in performance, 20 females and 31 males (mean ± SD; age, 27.6 ± 10.5 years; height, 176.7 ± 8.3 cm; mass, 77.3 ± 13.4 kg) were familiarized with the FF PFME and then completed the test on 6 separate days. Pre-test behaviours (e.g., sleep, diet) and test conditions (e.g., calibration, time of day) were consistent. Repeated-measures ANOVA revealed a significant decrease in completion time between tests 1 and 6 (18.7%) and between all sequential pairs (e.g., tests 1 and 2). There was also a small but significant increase in the fraction of total test time for task completion and a corresponding decrease in the time to transition between tasks. The performance improvements cannot be explained by differences in effort (heart rate and perceived exertion). Coefficient of variation for tests 1, 2, and 3 was 7% and for tests 4, 5, and 6 was 2.6%. The results indicate the importance of practice on performance and the potential for false-positive or false-negative decision errors if biological variability is not taken into account.

Establishment of performance standards and a cut-score for the Canadian Forces firefighter physical fitness maintenance evaluation (FF PFME).

The bookmark method for setting cut-scores was used to re-set the cut-score for the Canadian Forces Firefighter Physical Fitness Maintenance Evaluation (FF PFME). The time required to complete 10 tasks that together simulate a first-response firefighting emergency was accepted as a measure of work capacity. A panel of 25 Canadian Forces firefighter supervisors set cut-scores in three rounds. Each round involved independent evaluation of nine video work samples, where the times systematically increased from 400 seconds to 560 seconds. Results for Round 1 were discussed before moving to Round 2 and results for Round 2 were discussed before moving to Round 3. Accounting for the variability among panel members at the end of Round 3, a cut-score of 481 seconds (mean Round 3 plus 2 SEM) was recommended. Firefighters who complete the FF PFME in 481 seconds or less have the physical capacity to complete first-response firefighting work.

The effects of load and training pattern on acute neuromuscular responses in the upper body.

The purpose of this study was to examine the effects of repetition maximum (RM) loads and training patterns on acute neuromuscular responses in the upper body. Markers of fatigue were monitored under a descending pattern (DP), in which repetitions decreased in subsequent sets, and an ascending pattern (AP), in which repetitions increased in subsequent sets. Both training patterns were performed using 5- and 10-RM loads. Fatigue was assessed by monitoring changes in force output, motor unit activation and muscle twitch characteristics (peak twitch [PT], time to PT [TPT], and ½ relaxation time [RT]). All 4 protocols (5-RM DP, 5-RM AP, 10-RM DP, and 10-RM AP) produced significant decreases pre to postprotocol in force output, TPT, and ½RT. With the exception of 5-RM DP, all protocols produced significant decreases in motor unit activation. Pre to postprotocol, PT forces were potentiated under 5-RM loads, whereas they were depressed under 10-RM loads. Hence, a main effect for training protocols showed that changes in PT force were significantly different under 5-RM, as compared to 10-RM loads. The results indicate that central fatigue may be independent of load and pattern, whereas peripheral fatigue would appear to be dependent on load but not pattern.

The effects of different sit- and curl-up positions on activation of abdominal and hip flexor musculature.

The purpose of this study was to evaluate abdominal muscle activation with variations in trunk flexion (sit or curl up) positions, including the protocol currently used by the Canadian Society of Exercise Physiology (CSEP) Health and Fitness Program. Electromyographic (EMG) data were collected during isometric contractions from the upper rectus abdominis (URA), lower rectus abdominis (LRA), external obliques (EO), lower abdominal stabilizers (LAS), rectus femoris (RF), and the biceps femoris (BF) in 14 subjects. Sit-up positions were varied and randomized through 3 variables: the distance the hand traveled along the floor (5, 10, or 15 cm), bent knee or extended knee, and fixed or non-fixed feet. In regard to the distance the hand traveled along the floor, the 10 cm position produced the highest activation of the LRA (p = 0.02), the 5 cm distance produced the lowest RF activation (p = 0.001), and the 15 cm distance produced the lowest activation of the URA (p = 0.001). There was no significant difference between bent-knee and extended-leg sit-up positions; however, there was a trend (p = 0.1) showing that the bent-knee sit-up position produced higher levels of LAS activation and lower levels of RF activation. Foot fixation resulted in significantly lower activation levels of all abdominal sites and higher levels for the RF (p < 0.0001). The technique used for the CSEP Health and Fitness program partial curl- or sit-up test produced the highest or equal activation levels for all abdominal muscle sites.

Influence of pelvis position on the activation of abdominal and hip flexor muscles.

A pelvic position has been sought that optimizes abdominal muscle activation while diminishing hip flexor activation. Thus, the objective of the study was to investigate the effect of pelvic position and the Janda sit-up on trunk muscle activation. Sixteen male volunteers underwent electromyographic (EMG) testing of their abdominal and hip flexor muscles during a supine isometric double straight leg lift (DSLL) with the feet held approximately 5 cm above a board. The second exercise (Janda sit-up) was a sit-up action where participants simultaneously contracted the hamstrings and the abdominal musculature while holding an approximately 45 degrees angle at the knee. Root mean square surface electromyography was calculated for the Janda sit-up and DSLL under 3 pelvic positions: anterior, neutral, and posterior pelvic tilt. The selected muscles were the upper and lower rectus abdominis (URA, LRA), external obliques, lower abdominal stabilizers (LAS), rectus femoris, and biceps femoris. The Janda sit-up position demonstrated the highest URA and LRA activation and the lowest rectus femoris activation. The Janda sit-up and the posterior tilt were significantly greater (p < 0.01 and p < 0.05, respectively) than the anterior tilt for the URA and LRA muscles. Activation levels of the URA and LRA in neutral pelvis were significantly (p < 0.01 and p < 0.05, respectively) less than the Janda sit-up position, but not significantly different from the posterior tilt. No significant differences in EMG activity were found for the external obliques or LAS. No rectus femoris differences were found in the 3 pelvis positions. The results of this study indicate that pelvic position had a significant effect on the activation of selected trunk and hip muscles during isometric exercise, and the activation of the biceps femoris during the Janda sit-up reduced the activation of the rectus femoris while producing high levels of activation of the URA and LRA.

Postactivation potentiation of force is independent of h-reflex excitability.

UNLABELLED: The contractile history of muscle can potentiate electrically evoked force production. A link to voluntary force production, related in part to an increase in reflex excitability, has been suggested. PURPOSE: Our purpose was to quantify the effect of postactivation potentiation on voluntary force production and spinal H-reflex excitability during explosive plantar flexion actions. METHODS: Plantar flexor twitch torque, soleus H-reflex amplitudes, and the rate of force development of explosive plantar flexion were measured before and after 4 separate conditioning trials (3 x 5 s maximal contractions). RESULTS: Twitch torque and rate of force production during voluntary explosive plantar flexion were significantly increased (P < .05) while H-reflex amplitudes remained unchanged. Although twitch torque was significantly higher after conditioning, leading to a small increase in the rate of voluntary force production, this was unrelated to changes in reflex excitability. CONCLUSION: We conclude that postactivation potentiation may result in a minor increase in the rate of voluntary isometric force production that is unrelated to neural excitability.

The application of postactivation potentiation to elite sport.

Recently there has been considerable interest and research into the functional significance of postactivation potentiation (PAP) on sport performance. The interest has evolved around the potential for enhancing acute performance or the long-term training effect, typically in the form of complex training. Complex training usually involves performing a weight-training exercise with high loads before executing a plyometric exercise with similar biomechanical demands. Despite a considerable amount of research in the past 10 years it would seem there is still much research to be done to fully determine whether PAP has a functional role and, if so, how to best exploit it. It is clear from the research that there are many factors that need to be considered when attempting to apply PAP to an athlete. It is possible that a well-conceived sport-specific warm-up might be as or more effective in enhancing acute performance and easier to apply in a practical setting. In addition, despite its current popularity, there has not been 1 study that has effectively examined the efficacy of complex training and whether it has any advantage over other forms of training that combine weight training and plyometrics but not in the same training session.

The effects of varying time under tension and volume load on acute neuromuscular responses.

The purpose of this study was to examine the effects of different methods of measuring training volume, controlled in different ways, on selected variables that reflect acute neuromuscular responses. Eighteen resistance-trained males performed three fatiguing protocols of dynamic constant external resistance exercise, involving elbow flexors, that manipulated either time-under-tension (TUT) or volume load (VL), defined as the product of training load and repetitions. Protocol A provided a standard for TUT and VL. Protocol B involved the same VL as Protocol A but only 40% concentric TUT; Protocol C was equated to Protocol A for TUT but only involved 50% VL. Fatigue was assessed by changes in maximum voluntary isometric contraction (MVIC), interpolated doublet (ID), muscle twitch characteristics (peak twitch, time to peak twitch, 0.5 relaxation time, and mean rates of force development and twitch relaxation). All protocols produced significant changes (P

Increased spinal reflex excitability is not associated with neural plasticity underlying the cross-education effect.

The purpose of this study was to examine the effects of a 5-wk unilateral, isometric strength-training program on plasticity in the spinal Hoffmann (H-) reflex in both the trained and untrained legs. Sixteen participants, 22-42 yr old, were assigned to either a control (n = 6) or an exercise group (n = 10). Both groups were tested for plantar flexion maximal voluntary isometric contractions (MVIC) and soleus H-reflex amplitude in both limbs, at the beginning and at the end of a 5-wk interval. Participants in the exercise group showed significantly increased MVIC in both legs after training (P < 0.05), whereas strength was unchanged in the control group for either leg. Subjects in the exercise group displayed increased (P < 0.05) H-reflex amplitudes on the ascending limb of the recruitment curve (at an equivalent M wave of 5% of the maximal M wave, H(A)) only in the trained leg. Maximal H-reflex and M-wave remained unchanged with training. Increased amplitude of H(A) in the trained limb concurrent with increased strength suggests that spinal mechanisms may underlie the changes in strength, possibly because of increased alpha-motoneuronal excitability or reduced presynaptic inhibition. Despite a similar increase in strength in the contralateral limb of the exercise group, H(A) amplitude was unchanged. We conclude that the cross-education effect of strength training may be due to supraspinal to a greater extent than spinal mechanisms.

Dynamic training volume: a construct of both time under tension and volume load.

The purpose of this study was to investigate the effects of three different weight training protocols, that varied in the way training volume was measured, on acute muscular fatigue. Ten resistance-trained males performed all three protocols which involved dynamic constant resistance exercise of the elbow flexors. Protocol A provided a standard for the time the muscle group was under tension (TUT) and volume load (VL), expressed as the product of the total number of repetitions and the load that was lifted. Protocol B involved 40% of the TUT but the same VL compared to protocol A; protocol C was equated with protocol A for TUT but only involved 50% of the VL. Fatigue was assessed by changes in maximum voluntary isometric force and integrated electromyography (iEMG) between the pre- and post-training protocols. The results of the study showed that, when equated for VL, greater TUT produced greater overall muscular fatigue (p ≤ 0.001) as reflected by the reduction in the force generating capability of the muscle. When the protocols were equated for TUT, greater VL (p ≤ 0.01) resulted in greater overall muscular fatigue. All three protocols resulted in significant decreases in iEMG (p ≤ 0.05) but they were not significantly different from each other. It was concluded that, because of the importance of training volume to neuromuscular adaptation, the training volume needs to be clearly described when designing resistance training programs. Key PointsIncrease in either time under tension (TUT) or volume load (VL) increases the acute fatigue response, despite being equated for volume (by another method).A potential discrepancy in training volume may be present with training parameters that fail to control for either TUT or VL.Neural fatigue may be a contributing factor to the development of muscular fatigue but is not influenced by various methods of calculating volume such as TUT or VL.

The effect of training volume on the acute response and adaptations to resistance training.

PURPOSE: To examine the acute response to 2 resistance-exercise protocols performed to repetition failure, but different in load configuration, and determine whether the acute response was related to strength increases after 8 weeks of training. METHODS: Eighteen resistance-trained men completed a single session of 2 resistance-exercise protocols. The constant-load protocol (CL) required subjects to complete 3 sets of single-arm preacher curls (elbow flexion) to failure using a load of approximately 77% 1RM. The reduced-load protocol (RL) was similar, but training load was reduced for the second and third sets. Maximal isometric force (MVIC) and blood lactate were assessed preprotocol and postprotocol to determine the acute response. For the 8-week training phase, subjects (N = 12) were divided into 2 programs, each corresponding to 1 of the protocols. Strength was measured before and after training. RESULTS: MVIC decreased from 106.2 +/- 13.8 to 84.3 +/- 12.1 N . m and from 109.1 +/- 14.7 to 82.5 +/- 13 N . m after the CL and RL protocols, respectively. The decrements in MVIC were significant (P < .001), with the decline after RL tending to be greater (P = .051). Postprotocol blood lactate concentrations after CL and RL were 3.4 +/- 1.1 and 4.1 +/- 1.3 mmol/L, respectively, with greater increases after RL (P = .036). Similar and significant 1RM strength increases were observed after both programs (from 20.7 +/- 2.7 to 23.3 +/- 3.5 kg after CL and from 22.4 +/- 2.9 to 25.5 +/- 3.2 kg after RL; P < .001). CONCLUSION: The similar increases in strength suggest that either the greater acute response to RL was not related to the increases in strength or a minimal (threshold) response was achieved during both programs.

Effect of loading on enhancement of power performance over three consecutive trials.

The acute effects of maximal voluntary isometric contractions (MVICs) in the squat position on subsequent measures of power output over 3 consecutive sets were investigated. Sixteen trained men experienced with back squats participated in the study. A 7-second MVIC was performed 4 minutes before the execution of 5 maximal countermovement jumps (CMJs) and was repeated for 3 consecutive sets (protocol 1). The results were compared to power output performance in a similar protocol (protocol 2) that excluded the 7-second MVICs. No significant differences occurred in any of the power output measurements between protocol 1 and protocol 2, nor did significance occur linearly across the 4 sets of CMJ, with the exception of a decrease in peak power in protocol 2 (p < or = 0.05). Using both mean and maximal values only one significant correlation between either relative strength and performance enhancement or absolute strength and performance enhancement was present at p < or = 0.01. At p < or = 0.05, significant correlations were found between absolute strength and mean peak power (PP), mean peak acceleration (PA), mean peak force (PF), max PP, max PA, max PF, and max peak velocity. These data indicate that the execution of an MVIC performed before a power exercise was inadequate to acutely enhance power output over any of 3 consecutive trials.

Post-activation potentiation: underlying physiology and implications for motor performance.

The response of muscle to volitional or electrically induced stimuli is affected by its contractile history. Fatigue is the most obvious effect of contractile history reflected by the inability of a muscle to generate an expected level of force. However, fatigue can coexist with post-activation potentiation (PAP), which serves to improve muscular performance, especially in endurance exercise and activities involving speed and power. The measured response of muscular performance following some form of contractile activity is the net balance between processes that cause fatigue and the simultaneous processes that result in potentiation. Optimal performance occurs when fatigue has subsided but the potentiated effect still exists. PAP has been demonstrated using electrically induced twitch contractions and attributed to phosphorylation of myosin regulatory light chains, which makes actin and myosin more sensitive to Ca(2+). The potentiated state has also been attributed to an increase in alpha-motoneuron excitability as reflected by changes in the H-reflex. However, the significance of PAP to functional performance has not been well established. A number of recent studies have applied the principles of PAP to short-term motor performance as well as using it as a rationale for producing long-term neuromuscular changes through complex training. Complex training is a training strategy that involves the execution of a heavy resistance exercise (HRE) prior to performing an explosive movement with similar biomechanical characteristics, referred to as a complex pair. The complex pair is then repeated for a number of sets and postulated that over time will produce long-term changes in the ability of a muscle to generate power. The results of these studies are equivocal at this time and, in fact, no training studies have actually been undertaken. The discrepancies among the results of the various studies is due in part to differences in methodology and design, with particular reference to the mode and intensity of the HRE, the length of the rest interval within and between the complex pairs, the type of explosive activity, the training history of the participants, and the nature of the dependent variables. In addition, few of the applied studies have actually included measures of twitch response or H-reflex to determine if the muscles of interest are potentiated. There is clearly more research required in order to clarify the functional significance of PAP and, in particular, the efficacy of complex training in producing long-term neuromuscular adaptations.

Acute effects of heavy preloading on vertical and horizontal jump performance.

The purpose of this study was to investigate the acute effects of a heavy dynamic preload, consisting of 1 set of 5 repetition maximum (5RM) back squats, on countermovement vertical jump (VJ) and horizontal jump (HJ) performance. The study also investigated the ability of subjects to learn to apply the effects of the preload over subsequent training sessions. Nineteen (N = 19) resistance-trained men (age = 25.0 +/- 4.8 years; weight = 79.3 +/- 6.6 kg) participated in the study. Each subject took part in 4 practice and 4 testing sessions. The 4 practice sessions were included to allow for any learning effects of VJ and HJ to stabilize and to establish a true 5RM back squat. The 4 testing sessions were included to see if subjects were able to capitalize on the repeat exposure to the protocol. One practice session consisted of a 10-minute warm-up (5 minutes of cycling and 5 minutes of stretching), 2 sets of VJ and HJ (each set of VJ and HJ consisted of 4 jump repetitions) with a 5-minute rest between sets, progressive 5RM back squat evaluation, and 2 final sets of VJ and HJ. Both VJ and HJ increased approximately 2% over the 4 practice sessions, and 5RM back squat strength improved from 164.2 +/- 25.1 kg to 196.9 +/- 23.0 kg (p < or = 0.05). The 4 testing sessions each consisted of the standardized warm-up, 1 set of 4 VJs and HJs, a 5-minute rest, 5RM back squat, a 5-minute rest, and the final set of VJs and HJs. Pre- and post-5RM VJ and HJ order was randomly assigned. The results indicated no significant differences occurred between the mean or maximal values for either VJ or HJ as a consequence of the dynamic preload exercise. In addition, the results reflected an inability of subjects to benefit from the repeated exposure to the heavy dynamic preload exercise protocol.

The effects of accentuated eccentric loading on strength, muscle hypertrophy, and neural adaptations in trained individuals.

The purpose of this study was to compare the strength and neuromuscular adaptations for dynamic constant external resistance (DCER) training and dynamic accentuated external resistance (DAER) training (resistance training employing an accentuated load during eccentric actions). Male subjects active in resistance training were assigned to either a DCER training group (n = 10) or a DAER training group (n = 8) for 9 weeks. Subjects in the DCER group performed 4 sets of 10 repetitions with a load of 75% concentric 1 repetition maximum (RM). Subjects in the DAER group performed 3 sets of 10 repetitions with a concentric load of 75% of 1RM and an eccentric load of approximately 120% of concentric 1RM. Three measures reflecting adaptation of elbow flexors and extensors were recorded pretraining and posttraining: concentric 1RM, muscle cross-sectional area (CSA), and specific tension. Strength was assessed at midtraining periods. No significant changes in muscle CSA were observed in either group. Both training groups experienced significant increases in concentric 1RM and specific tension of both the elbow flexors and extensors, but compared with DCER training, DAER training produced significantly greater increases in concentric 1RM of the elbow extensors. These results suggest that, for some exercises, DAER training may be more effective than DCER training in developing strength within a 9-week training phase. However, for trained subjects, neither protocol is effective in eliciting muscle hypertrophy.