The physiological and mechanical demands of aerobics, indoor cycling, and netball in recreationally active females

Abstract Background Group-based exercise is a popular method of improving fitness. However, limited research exists on the mul- tidisciplinary responses to group-based exercise. Aims The aim of this study was to compare the physiological and mechanical demands of aerobics, indoor group cycling, and netball. Methods Fourteen recreationally active females (age 20 ± 2 years, body height 1.65 ± 0.09 m, body mass 65.9 ± 11.8 kg, body fat 26.3 ± 7.2%) participated in three experimental trials (aerobics, indoor cycling, netball) in a randomised order with 1 week intervening. Heart rate, blood lactate, RPE and PlayerLoadTM were measured. Results A repeated-measures ANOVA revealed mean and peak heart rate (beats·min−1) were lower (P < 0.05) for aerobics (130 ± 114; 176 ± 18) than indoor cycling (150 ± 9; 191 ± 9) and netball (144 ± 11; 195 ± 6), respectively. Blood lactate (mmol·L−1) was higher (P < 0.001) after indoor cycling (5.6 ± 2.6) compared to aerobics (2.2 ± 1.4) and netball (2.5 ± 1.1). RPE was not different between trials. PlayerLoadTM (a.u) during indoor cycling (213.9 ± 46.9) was lower (P < 0.05) than netball (358.5 ± 94.5) and aerobics (296.9 ± 99.0). Conclusions Theseresultssuggestindoorcyclingstimulatesgreaterphysiologicaldemands,whilstnetballandaerobicselicit a higher PlayerLoadTM corresponding to higher mechanical demands. These findings may have implications for exercise prescription in recreationally active females

Intermittent treadmill running induces kinematic compensations to maintain soccer kick foot speed despite no change in knee extensor strength

Kicking is a fundamental skill and a primary noncontact mechanism of injury in soccer, with injury incidence increasing during the latter stages of match-play. Ten male professional soccer players completed a 90-minute treadmill protocol based on the velocity profile of soccer match-play. Preexercise, and at 15-minute intervals, players completed a maximal velocity kick subjected to kinematic analysis at 200 Hz. Preexercise, and at the end of each half, players also completed isokinetic concentric knee extensor repetitions at 180°·s−1, 300°·s−1, and 60°·s−1. Kicking foot speed was maintained at ∼19 m·s−1, with no main effect for exercise duration. In relation to proximal–distal sequencing during the kicking action, there was a significant increase in the duration (but not magnitude) of thigh rotation, with a compensatory decrease in the duration (but not magnitude) of shank rotation during the latter stages of the exercise protocol. In relation to long-axis rotation, pelvic orientation at ball contact was maintained at ∼6°, representing a total pelvic rotation in the order of ∼15° during the kicking action. Peak knee extensor torque at all speeds was also maintained throughout the protocol, such that kinematic modifications are not attributable to a decline in knee extensor strength.</jats:p

Lumbar and cervico-thoracic spine loading during a fast bowling spell:Lumbar and cervico-thoracic spine loading during a fast bowling spell

Context: Epidemiological studies highlight a prevalence of lumbar vertebrae injuries in cricket fast bowlers, with governing bodies implementing rules to reduce exposure. Analysis typically requires complex and laboratory-based biomechanical analyses, lacking ecological validity. Developments in GPS microtechnologies facilitate on-field measures of mechanical intensity, facilitating screening toward prevention and rehabilitation. Objective: To examine the efficacy of using GPS-mounted triaxial accelerometers to quantify accumulated body load and to investigate the effect of GPS-unit placement in relation to epidemiological observations. Design: Repeated measures, field-based. Setting: Regulation cricket pitch. Participants: 10 male injury-free participants recruited from a cricket academy (18.1 ± 0.6 y). Intervention: Each participant was fitted with 2 GPS units placed at the cervicothoracic and lumbar spines to measure triaxial acceleration (100 Hz). Participants were instructed to deliver a 7-over spell of fast bowling, as dictated by governing-body guidelines. Main Outcome Measures: Triaxial total accumulated body and the relative uniaxial contributions were calculated for each over. Results: There was no significant main effect for overs bowled, in either total load or the triaxial contributions to total load. This finding suggests no cumulative fatigue effect across the 10-over spell. However, there was a significant main effect for GPS-unit location, with the lumbar unit exposed to significantly greater load than the cervicothoracic unit in each of the triaxial planes. Conclusions: There was no evidence to suggest that accumulated load significantly increased as a result of spell duration. In this respect the governing-body guidelines for this age group can be considered safe, or potentially even conservative. However, the observation of higher body load at the lumbar spine than at the cervicothoracic spine supports epidemiological observations of injury incidence. GPS microtechnologies might therefore be considered in screening and monitoring of players toward injury prevention and/or during rehabilitation

Attentional focusing instructions influence quadriceps activity characteristics but not force production during isokinetic knee extensions

The attentional focus emphasised in verbal instruction influences movement and muscle recruitment characteristics, with an external focus (onto movement effects) typically benefiting performance. However, contrasting findings suggest either a selective isolation or spreading activation effect on associated muscles as a result of internally focused instruction (movement characteristics). In the present experiment, participants completed maximal isokinetic concentric leg extension exercise using internally (muscle specific: vastus medialis oblique) or externally (outcome specific) focused instructions. Integrated Electromyography (iEMG) of the vastus lateralis, vastus medialis oblique and rectus femoris muscles was obtained in addition to knee extensor torque. There were no differences in torque production between conditions. Externally focused instruction produced significantly lower iEMG magnitude across muscles, whereas an internal focus produced the greatest activity but with no evidence of a selective isolation effect of the vastus medialis oblique. The muscle-specific internal focus of attention resulted in a spreading activation effect, such that activity is elevated in muscles not within the focus of attention. Whilst an external focus did not improve performance, force was produced with lower muscular activity reflecting increased efficiency. The resultant noise in the motor system associated with an internal focus inhibits movement economy and attempts at selective activation

Sub-maximal cricket fast bowling offers a disproportionate reduction in loading vs performance: An alternative workload intervention

Context: Cricket fast bowlers are particularly susceptible to lumbar spine loading and injury. Quantitative analysis of technique typically involves laboratory-based biomechanical systems with limited ecological validity, whereas contemporary developments in GPS microtechnologies facilitate on-field evaluation of loading. Objective: To quantify the influence of sub-maximal bowling from reduced approach lengths on performance and loading. Design: Repeated measures, field-based. Setting: Regulation cricket pitch. Participants: 12 male cricket academy fast bowlers (18.7 ± 0.7 y), injury free with ≥3 years competitive experience. Interventions: Each bowler wore 2 GPS units placed at C7 and L4 to measure triaxial acceleration (100 Hz). Bowlers completed an over (six deliveries) from a randomised 3, 6, 9, and 12 stride approach. Main Outcome Measures: Ball speed was recorded as the performance measure, with PlayerLoad in the anteroposterior, mediolateral and vertical planes also calculated for each delivery length. Results: In ball speed there was a significant main effect for delivery length (P = 0.016), with a 3 stride approach eliciting significantly less ball speed than a 9 (P = 0.032) or 12 (P = 0.002) stride approach. In loading, there was a significant (P &lt; 0.001) main effect for delivery length in the anteroposterior, mediolateral, and vertical planes, with loading increasing linearly as a function of delivery strides. The 6 stride approach elicited a 44% reduction in loading, with a disproportionately small 3.5% decrease in performance. There was a significant main effect for GPS location in all planes (P ≤ 0.023), with L4 eliciting greater loading than C7. Conclusions: A sub-maximal 6 stride approach yielded the optimum balance between reduced loading and performance inhibition. Reduced delivery length therefore offers an alternative to reduced overs in reducing loading in young bowlers, and might also have practicable value in the rehabilitation of bowlers post-injury

Temporal pattern of kinesiology tape efficacy on hamstring extensibility

BACKGROUND: Kinesiology tape has been advocated as a means of improving muscle flexibility, a potential modifiable risk factor for injury, over time. The epidemiology and etiology of hamstring injuries in sport have been well documented. PURPOSE: To compare the temporal pattern of efficacy of kinesiology tape and traditional stretching techniques on hamstring extensibility over a five day period. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty recreationally active male participants (Mean ± SD: age 20.0 ± 1.55 years; height 179.3 ± 4.94 cm; mass 76.9 ± 7.57 kg) completed an active knee extension assessment (of the dominant leg) as a measure of hamstring extensibility. Three experimental interventions were applied in randomized order: Kinesiology tape (KT), static stretch (SS), proprioceptive neuromuscular facilitation (PNF). Measures were taken at baseline, +1min, + 30mins, + 3days and +5days days after each intervention. The temporal pattern of change in active knee extension was modelled as a range of regression polynomials for each intervention, quantified as the regression coefficient. RESULTS: Hamstring ROM with KT application at +3days was significantly greater than baseline (129.18 ± 15.46%, p = 0.01), SS (106.99 ± 9.84%, p = 0.03) and PNF (107.42 ± 136.13%, p = 0.03) interventions. The temporal pattern of changes in ROM for SS and PNF were best modelled by a negative linear function, although the strength of the correlation was weak in each case. In contrast, the KT data was optimised using a quadratic polynomial function (r(2) = 0.60), which yielded an optimum time of 2.76 days, eliciting a predicted ROM of 129.6% relative to baseline. CONCLUSION: Each intervention displayed a unique temporal pattern of changes in active knee extension. SS was best suited to immediate improvements, and PNF to +30 minutes in hamstring extensibility, whereas kinesiology tape offered advantages over a longer duration, peaking at 2.76 days. These findings have implications for the choice of intervention, timing and duration to assist clinicians in both a sporting and clinical context. LEVEL OF EVIDENCE: 2

Is there a role for GPS in determining functional ankle rehabilitation progression criteria? A preliminary study

Context: Contemporary developments in Global Positioning System (GPS) technology present a means of quantifying mechanical loading in a clinical environment with high ecological validity. However, applications to date have typically focused on performance rather than rehabilitation. Objective: To examine the efficacy of GPS microtechnology in quantifying the progression of loading during functional rehabilitation from ankle sprain injury, given the prevalence of reinjury and need for quantifiable monitoring. Furthermore, to examine the influence of unit placement on the clinical interpretation of loading during specific functional rehabilitation drills. Design: Repeated measures. Setting: University athletic facilities. Participants: Twenty-two female intermittent team sports players. Intervention: All players completed a battery of 5 drills (anterior hop, inversion hop, eversion hop, diagonal hop, and diagonal hurdle hop) designed to reflect the mechanism of ankle sprain injury, and progress functional challenge and loading. Main Outcome Measures: GPS-mounted accelerometers quantified uniaxial PlayerLoad for each drill, with units placed at C7 and the tibia. Main effects for drill type and GPS location were investigated. Results: There was a significant main effect for drill type (P &lt; .001) in the mediolateral (η2 = .436), anteroposterior (η2 = .480), and vertical planes (η2 = .516). The diagonal hurdle hop elicited significantly greater load than all other drills, highlighting a nonlinear progression of load. Only the mediolateral load showed evidence of progressive increase in loading. PlayerLoad was significantly greater at the tibia than at C7 for all drills, and in all planes (P &lt; .001, η2 ≥ .662). Furthermore, the tibia placement was more sensitive to between-drill changes in mediolateral load than the C7 placement. Conclusions: The placement of the GPS unit is imperative to clinical interpretation, with both magnitude and sensitivity influenced by the unit location. GPS does provide efficacy in quantifying multiplanar loading during (p)rehabilitation, in a field or clinical setting, with potential in extending GPS analyses (beyond performance metrics) to functional injury rehabilitation and prevention.</p

Contemporary Approaches to Isokinetic Strength Assessments in Professional Football Players.

To assess traditional and novel isokinetic strength characteristics of the eccentric knee flexor (eccKF) and concentric knee extensor (conKE) musculature, 26 professional football players completed bilateral conKE and eccKF contractions at angular velocities of 180, 270, and 60 °·s-1. Peak torque (PT), angle of peak torque (APT), angle-specific torque (AST) analysed every 10° between 40 and 70°, functional range (FR), and dynamic control ratios (DCR) calculated from both the PT (DCRPT) and AST data (DCRAST) were analysed. The PT, APT, and FR data elicited significant contraction*angular velocity interactions (P< 0.001).Significant main effects for contraction*angular velocity*angle and contraction*angular velocity*limb*angle interactions (P< 0.001) were identified for AST data. The DCRPT data elicited a significant main effect for angular velocity (P< 0.001) and limb (P= 0.018), whereas the DCRAST data was significantly different across angles (P< 0.001) and elicited a significant (P= 0.002) limb*angle interaction. Traditional analysis variables utilised for isokinetic strength assessments in football may not be appropriate and/or sensitive enough to identify injury risk. Practitioners should utilise the novel metrics proposed in the current study and conduct assessments across a range of joint angles and angular velocities

The efficacy of elastic therapeutic tape variations on measures of ankle function and performance

Objectives: To investigate the effects of different variations of elastic therapeutic taping (ETT) on tests used to screen for ankle injury risk and function. Design: Randomized crossover. Setting: Laboratory. Participants: Twelve professional male soccer players completed three experimental trials: No tape (NT), RockTape™ (RT), and Kinesio™ Tape (KT) applied to the ankle complex. Outcome Measures: Clinical and functional ankle screening tests were used to assess the effects of ETT on measures of joint position sense, postural stability and ground reaction forces. Results: KT (P = 0.04) and RT (P = 0.01) demonstrated significant improvements in end range joint position sense. When compared to NT, RT significantly (P = 0.02) improved mid-range joint position sense at 15° and time to complete a drop landing task. No significant differences were observed for measures of postural stability (P ≥ 0.12) nor ground reaction force variables (P ≥ 0.33). Conclusions: Results advocate the use of ETT for proprioceptive and functional tasks when applied to the ankles of healthy male soccer players. However, a greater number of practical and significant differences were observed when RT only was applied, indicating that practitioners may potentially advocate the use of RT for tasks requiring proprioception and functional performance.</p