Lower-extremity muscle activity during aquatic and land treadmill running at the same speeds.

CONTEXT

Muscle activation during aquatic treadmill (ATM) running has not been examined, despite similar investigations for other modes of aquatic locomotion and increased interest in ATM running.

OBJECTIVES

The objectives of this study were to compare normalized (percentage of maximal voluntary contraction; %MVC), absolute duration (aDUR), and total (tACT) lower-extremity muscle activity during land treadmill (TM) and ATM running at the same speeds.

DESIGN

Exploratory, quasi-experimental, crossover design.

SETTING

Athletic training facility.

PARTICIPANTS

12 healthy recreational runners (age = 25.8 ± 5 y, height = 178.4 ± 8.2 cm, mass = 71.5 ± 11.5 kg, running experience = 8.2 ± 5.3 y) volunteered for participation.

INTERVENTION

All participants performed TM and ATM running at 174.4, 201.2, and 228.0 m/min while surface electromyographic data were collected from the vastus medialis, rectus femoris, gastrocnemius, tibialis anterior, and biceps femoris.

MAIN OUTCOME MEASURES

For each muscle, a 2 × 3 repeated-measures ANOVA was used to analyze the main effects and environment-speed interaction (P ≤ .05) of each dependent variable: %MVC, aDUR, and tACT.

RESULTS

Compared with TM, ATM elicited significantly reduced %MVC (-44.0%) but increased aDUR (+213.1%) and tACT (+41.9%) in the vastus medialis, increased %MVC (+48.7%) and aDUR (+128.1%) in the rectus femoris during swing phase, reduced %MVC (-26.9%) and tACT (-40.1%) in the gastrocnemius, increased aDUR (+33.1%) and tACT (+35.7%) in the tibialis anterior, and increased aDUR (+41.3%) and tACT (+29.2%) in the biceps femoris. At faster running speeds, there were significant increases in tibialis anterior %MVC (+8.6-15.2%) and tACT (+12.7-17.0%) and rectus femoris %MVC (12.1-26.6%; swing phase).

CONCLUSION

No significant environment-speed interaction effects suggested that observed muscle-activity differences between ATM and TM were due to environmental variation, ie, buoyancy (presumed to decrease %MVC) and drag forces (presumed to increase aDUR and tACT) in the water.