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High versus low contextual interference in simulation-based training of troubleshooting skills: effects on transfer performance and invested mental effort

The effects of contextual interference on practice behavior, transfer performance, and cognitive load for learning troubleshooting skills were studied. A low contextual interference (LCI) condition, in which subjects practiced to diagnose system failures in a blocked schedule, was compared with a high contextual interference (HCI) condition, in which failures were practiced in a random schedule. The following hypotheses are stated. Hypothesis 1: during practice, subjects in the HCI group will require more time to reach a high performance level (i.e., more accurate and/or faster diagnoses of system failures) on practice problems and will have to invest more mental effort relative to subjects in the LCI group. Hypothesis 2: subjects in the HCI group will show higher performance and lower invested mental effort on far transfer test problems, relative to subjects in the LCI group, but there will be no difference between the groups on near transfer test problems. The results showed that subjects in the HCI group were more accurate in diagnosing far transfer problems, although during practice they needed more time to diagnose system failures and made significantly more incorrect diagnoses.






Contextual Interference Effects on the Acquisition, Retention, and Transfer of a Motor Skill.

Retention and transfer of motor tasks was greater for high interference (random) acquisition groups than for low interference (blocked) acquisition groups. This effect was most notable when transfer was measured for the transfer task of greatest complexity. Results support Battig's conceptualization of contextual interference effects on retention and transfer. (Author/CP)







Contextual interference effects with skilled baseball players.

Department of Physical Education and Kinesiology, California Polytechnic State University, San Luis Obispo 93407.

The learning benefits of contextual interference have been frequently demonstrated in different settings using novice learners. The purpose of the present study was to test such effects with skilled athletic performers. Scheduling differences for biweekly additional ("extra") batting-practice sessions of a collegiate baseball team were examined. 30 players (ns = 10) were blocked on skill and then randomly assigned to one of three groups. The random and blocked groups received 2 additional batting-practice sessions each week for 6 wk. (12 sessions), while the control group received no additional practice. The extra sessions consisted of 45 pitches, 15 fastballs, 15 curveballs, and 15 change-up pitches. The random group received these pitches in a random order, while the blocked group received all 15 of one type, then 15 of the next type, and finally 15 of the last type of pitch in a blocked fashion. All subjects received a pretest of 45 randomly presented pitches of the three varieties. After 6 wk. of extra batting practice, all subjects received two transfer tests, each of 45 trials; one was presented randomly and one blocked. The transfer tests were counterbalanced across subjects. Pretest analysis showed no significant differences among groups. On both the random and blocked transfer tests, however, the random group performed with reliably higher scores than the blocked group, who performed better than the control group. When comparing the pretest to the random transfer test, the random group improved 56.7%, the blocked group 24.8%, and the control group only 6.2%.(ABSTRACT TRUNCATED AT 250 WORDS)








Muscular coactivation The role of the antagonist musculature in maintaining knee stability

The objective of this study was to quantify the coacti vation patterns of the knee flexor and extensor muscles as part of continued efforts to identify the role of the antagonist muscles in maintaining joint stability.

The simultaneous EMG from the flexor and extensor muscles of the knee were recorded during maximal effort, slow isokinetic contractions (15 deg/sec) on the plane parallel to the ground to eliminate the effect of gravity. The processed EMG from the antagonist mus cle was normalized with respect to its EMG as agonist at maximal effort for each joint angle. The plots of normalized antagonist EMG versus joint angle for each muscle group were shown to relate inversely to their moment arm variations over the joint range of motion. Additional calculations demonstrated that the antago nist exerts nearly constant opposing torque throughout joint range of motion. Comparison of data recorded from normal healthy subjects with that of high perform ance athletes with hypertrophied quadriceps demon strated strong inhibitory effects on the hamstrings coac tivations. Athletes who routinely exercise their ham strings, however, had a coactivation response similar to that of normal subjects.

We concluded that coactivation of the antagonist is necessary to aid the ligaments in maintaining joint stability, equalizing the articular surface pressure dis tribution, and regulating the joint's mechanical imped ance. The reduced coactivation pattern of the unexer cised antagonist to a hypertrophied muscle increases the risk of ligamentous damage, as well as demon strates the adaptive properties of the antagonist muscle in response to exercise. It was also concluded that reduced risk of knee injuries in high performance ath letes with muscular imbalance could result from com plementary resistive exercise of the antagonist muscle.

Fatigue, Vertical Leg Stiffness, and Stiffness Control Strategies in Males and Females

 Context: Fatigue appears to influence musculoskeletal injury rates during athletic activities, but whether males and females respond differently to fatigue is unknown.
Objective: To determine the influence of fatigue on vertical leg stiffness (K VERT) and muscle activation and joint movement strategies and whether healthy males and females respond similarly to fatigue.
Design: Repeated-measures design with all data collected during a single laboratory session.
Setting: Laboratory.
Patients or Other Participants: Physically active males (n = 11) and females (n = 10).
Intervention(s): Subjects performed hopping protocols at 2 frequencies before and after fatigue, which was induced by repeated squatting at submaximal loads.
Main Outcome Measure(s): We measured K VERT with a forceplate and peak muscle activity of the quadriceps, hamstrings, gastrocnemius, soleus, and anterior tibialis muscles with surface electromyography. Sagittal-plane kinematics at the knee and ankle were recorded with an electrogoniometer.
Results: After fatigue, K VERT was unchanged for all subjects. However, both males and females demonstrated reduced peak hamstrings ( P = .002) and anterior tibialis ( P = .001) activation, coupled with increased gastrocnemius ( P = .005) and soleus ( P = .001) peak activity, as well as increased quadriceps-hamstrings ( P = .005) and gastrocnemius/soleus-anterior tibialis coactivation ratios ( P = .03) after fatigue. Overall, females demonstrated greater quadriceps-hamstrings coactivation ratios than males, regardless of the fatigue condition ( P = .026). Only females showed increased knee flexion at initial contact after fatigue during hopping ( P = .03).
Conclusions: Although K VERT was unaffected, the peak muscle activation and joint movement strategies used to modulate K VERT were affected after fatigue. Once fatigued, both males and females used an ankle-dominant strategy, with greater reliance on the ankle musculature and less on the knee musculature. Also, once fatigued, all subjects used an antagonist inhibition strategy by minimizing antagonist coactivation. Overall, females used a more quadriceps-dominant strategy than males, showing greater quadriceps activity and a larger quadriceps-hamstrings coactivation ratio. Changes in muscle activation and coactivation ratios because of fatigue and sex are suggested to alter knee joint stability and increase anterior cruciate ligament injury risk.







Motor programming during practice conditions high and low in contextual interference.

Random practice has been reported to demand greater time for movement preparation during acquisition than blocked practice. The present study revealed that this could be attributed to a more complete engagement of the motor programming process during random practice. This cost, however, was localized to the motor programming subprocess that S. T. Klapp (1995) associated with organizing the internal structure of a movement chunk rather than an alternative subprocess responsible for organizing movement chunks into the correct serial order. The more thorough employment of motor programming during acquisition by random practice participants resulted in a more efficient use of this planning operation during retention, as well as more accurate movement reproduction. These data support the claim that practice conditions high in contextual interference support improvements in both movement preparation and memory strength. (PsycINFO Database Record (c) 2008 APA, all rights reserved)





Effect of sex hormones on neuromuscular control patterns during landing

The purpose of the study was to investigate the effects of sex hormones across menstrual cycle phases on lower extremity neuromuscular control patterns during the landing phase of a drop jump. A repeated-measures design was utilized to examine sex hormone effects in 26 recreationally active eumenorrheic women. Varus/valgus knee angle and EMG activity from six lower extremity muscles were recorded during three drop jumps from a 50cm platform in each phase of the menstrual cycle. Blood assays verified sex hormone levels and cycle phase. The semitendinosus muscle exhibited onset delays (p?0.006) relative to ground contact during the luteal phase, and demonstrated a significant (p?0.05) difference between early and late follicular phases. Muscle timing differences between the gluteus maximus and semitendinosus were decreased (p?0.05) in the luteal compared to early follicular phases. These results suggest a different co-contractive behavior between the gluteus maximus and semitendinosus, signifying a shift in neuromuscular control patterns. It appears that female recreational athletes utilize a different neuromuscular control pattern for performing a drop jump sequence when estrogen levels are high (luteal phase) compared to when they are low (early follicular phase).