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Ming-Chang Tsai and Scott G. Thomas

Purpose:

To validate the 3-minute all-out exercise test (3MT) protocol against the traditional critical-speed (CS) model (CSM) in front-crawl swimming.

Methods:

Ten healthy swimmers or triathletes (mean ± SD age 35.2 ± 10.5 y, height 176.5 ± 5.4 cm, body mass 69.6 ± 8.2 kg) completed 5 tests (3MT, 100m, 200m, 400m, 800m) over 2 wk on separate days. Traditional CS and anaerobic distance capacity (D′) were determined for each of the 3 traditional CSMs (linear distance-time, LIN; linear speed/time, INV; nonlinear time-speed, NLIN) from the 4 set-distance time trials. For the 3MT, CS was determined as the mean speed during the final 30 s of the test and D′ was estimated as the power-time integral above the CS.

Results:

Our results indicated no significant difference between the CS estimates determined from the traditional CSM and 3MT except for the INV model (P = .0311). Correlations between traditional CSMs and 3MT were high (r = .95, P < .01) However, D′ differed and post hoc analysis indicated that D′ estimated from 3MT was significantly lower than LIN (P = .0052) and NLIN (P < .0001). Correlations were weak (r < .55, P > .1). In addition, Bland-Altman plots between the traditional CSMs and 3MT CS estimates showed scattered points above and below the zero line, suggesting there is no consistent bias of one approach versus the other.

Conclusions:

The 3MT is a valid protocol for swimming to estimate CS. The demonstrated concurrent validity of the 3MT may allow more widespread use of CSMs to evaluate participants and responses to training.

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Abbey C. Thomas, Scott G. McLean and Riann M. Palmieri-Smith

Neuromuscular fatigue exacerbates abnormal landing strategies, which may increase noncontact anterior cruciate ligament (ACL) injury risk. The synergistic actions of quadriceps and hamstrings (QH) muscles are central to an upright landing posture, though the precise effect of simultaneous fatigue of these muscles on landing and ACL injury risk is unclear. Elucidating neuromechanical responses to QH fatigue thus appears important in developing more targeted fatigue-resistance intervention strategies. The current study thus aimed to examine the effects of QH fatigue on lower extremity neuromechanics during dynamic activity. Twenty-five healthy male and female volunteers performed three single-leg forward hops onto a force platform before and after QH fatigue. Fatigue was induced through sets of alternating QH concentric contractions, on an isokinetic dynamometer, until the first five repetitions of a set were performed at least 50% below QH peak torque. Three-dimensional hip and knee kinematics and normalized (body mass × height) kinetic variables were quantified for pre- and postfatigue landings and subsequently analyzed by way of repeated- measures mixed-model ANOVAs. QH fatigue produced significant increases in initial contact (IC) hip internal rotation and knee extension and external rotation angles (p < .05), with the increases in knee extension and external rotation being maintained at the time of peak vertical ground reaction force (vGRF) (p < .05). Larger knee extension and smaller knee fexion and external rotation moments were also evident at peak vGRF following fatigue (p < .05). Females landed with greater hip fexion and less abduction than males at both IC and peak vGRF as well as greater knee fexion at peak vGRF (p < .05). The peak vGRF was larger for females than males (p < .05). No sex × fatigue effects were found (p > .05). Fatigue of the QH muscles altered hip and knee neuromechanics, which may increase the risk of ACL injury. Prevention programs should incorporate methods aimed at countering QH fatigue.

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Danielle M. Dobney, Scott G. Thomas, Tim Taha and Michelle Keightley

Context: Baseline testing is a common strategy for concussion assessment and management. Research continues to evaluate novel measures for potential to improve baseline testing methods. Objectives: The primary objective was to (1) determine the feasibility of including physiological, neuromuscular, and mood measures as part of baseline concussion testing protocol, (2) describe typical values in a varsity athlete sample, and (3) estimate the influence of concussion history on these baseline measures. Design: Prospective observational study. Setting: Ryerson University Athletic Therapy Clinic. Participants: One hundred varsity athletes. Main Outcome Measures: Frequency and domain measures of heart rate variability, blood pressure, grip strength, profile of mood states—short form, and the Sport Concussion Assessment Tool-2. Results: Physiological, neuromuscular performance, and mood measures were feasible at baseline. Participants with a history of 2 or more previous concussions displayed significantly higher diastolic blood pressure. Females reported higher total mood disturbance compared with males. Conclusions: Physiological and neuromuscular performance measures are safe and feasible as baseline concussion assessment outcomes. History of concussion may have an influence on diastolic blood pressure.

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Lindsey K. Lepley, Abbey C. Thomas, Scott G. McLean and Riann M. Palmieri-Smith

Context:

As individuals returning to activity after anterior cruciate ligament reconstruction (ACLr) likely experience fatigue, understanding how fatigue affects knee-muscle activation patterns during sport-like maneuvers is of clinical importance. Fatigue has been suggested to impair neuromuscular control strategies. As a result, fatigue may place ACLr patients at increased risk of developing posttraumatic osteoarthritis (OA).

Objective:

To determine the effects of fatigue on knee-muscle activity post-ACLr.

Design:

Case control.

Setting:

University laboratory.

Participants:

12 individuals 7–10 mo post-ACLr (7 male, 5 female; age 22.1 ± 4.7 y; 1.8 ± 0.1 m; mass 77.7 ± 11.9 kg) and 13 controls (4 male, 9 female; age 22.9 ± 4.3 y; 1.7 ± 0.1 m; mass 66.9 ± 9.8 kg).

Interventions:

Fatigue was induced via repetitive sets of double-leg squats (n = 8), which were interspersed with sets of single-leg landings (n = 3), until squats were no longer possible.

Main Outcome Measures:

2 × 2 repeated-measures ANOVA was used to detect the main effects of group (ACLr, control) and fatigue state (prefatigue, postfatigue) on quadriceps:hamstring cocontraction index (Q:H CCI).

Results:

All subjects demonstrated higher Q:H CCI at prefatigue compared with postfatigue (F 1,23 = 66.949, P ≤ .001). Q:H CCI did not differ between groups (F 1,23 = 0.599, P = .447).

Conclusions:

The results indicate that regardless of fatigue state, ACLr individuals are capable of restoring muscle-activation patterns similar to those in healthy subjects. As a result, excessive muscle cocontraction, which has been hypothesized as a potential mechanism of posttraumatic OA, may not contribute to joint degeneration after ACLr.