Activity and functions of the human gluteal muscles in walking, running, sprinting, and climbing.

It has been suggested that the uniquely large gluteus maximus (GMAX) muscles were an important adaptation during hominin evolution based on numerous anatomical differences between humans and extant apes. GMAX electromyographic (EMG) signals have been quantified for numerous individual movements, but not across the range of locomotor gaits and speeds for the same subjects. Thus, comparing relative EMG amplitudes between these activities has not been possible. We assessed the EMG activity of the gluteal muscles during walking, running, sprinting, and climbing. To gain further insight into the function of the gluteal muscles during locomotion, we measured muscle activity during walking and running with external devices that increased or decreased the need to control either forward or backward trunk pitch. We hypothesized that 1) GMAX EMG activity would be greatest during sprinting and climbing and 2) GMAX EMG activity would be modulated in response to altered forward trunk pitch demands during running. We found that GMAX activity in running was greater than walking and similar to climbing. However, the activity during sprinting was much greater than during running. Further, only the inferior portion of the GMAX had a significant change with altered trunk pitch demands, suggesting that the hip extensors have a limited contribution to the control of trunk pitch movements during running. Overall, our data suggest that the large size of the GMAX reflects its multifaceted role during rapid and powerful movements rather than as a specific adaptation for a single submaximal task such as endurance running.

A descriptive study of the U.S. Marine Corps fitness tests (2000-2012).

This article describes the performance of active duty U.S. Marines on the Physical Fitness Test (PFT) and Combat Fitness Test (CFT) during calendar years 2000 through 2012. Our study sample included PFT composite scores (n = 543,185), PFT and CFT composite scores (n = 160,936), and PFT and CFT event scores (n = 135,926 and n = 201,953, respectively). In general, all Marines performed very well on each fitness test, with overall annual improvements. Interestingly, the majority of female Marines passed the minimum male standard on the CFT. Further studies will evaluate the relationship of fitness test performance and injury.

Vestibular physical therapy intervention: utilizing a computer assisted rehabilitation environment in lieu of traditional physical therapy.

Advanced technology such as virtual reality or immersive environments increases the complexities and challenges therapists can impose on their patients. In this study, four patients with mild traumatic brain injury utilized a Computer Assisted Rehabilitation Environment (CAREN) in place of traditional vestibular physical therapy. Patients visited the CAREN twice weekly for 6 weeks. Therapy sessions included a variety of applications that tasked the cognitive and physical capabilities of individual patients. After the 6 weeks, all patients showed improvement on balance, gait and visual measures. Virtual reality based therapy is an engaging and effective tool to treat patients with deficiencies related to a prior brain injury.

Changing the demand on specific muscle groups affects the walk-run transition speed.

It has been proposed that muscle-specific factors trigger the human walk-run transition. We investigated if changing the demand on trigger muscles alters the preferred walk-run transition speed. We hypothesized that (1) reducing the demand on trigger muscles would increase the transition speed and (2) increasing the demand on trigger muscles would decrease the transition speed. We first determined the normal preferred walk-run transition speed (PTS) using a step-wise protocol with a randomized speed order. We then determined PTS while subjects walked with external devices that decreased or increased the demand on specific muscle groups. We concurrently measured the electromyographic activity of five leg muscles (tibialis anterior, soleus, rectus femoris, medial and lateral gastrocnemius) at each speed and condition. For this study, we developed a dorsiflexor assist device that aids the dorsiflexor muscles. A leg swing assist device applied forward pulling forces at the feet thus aiding the hip flexors during swing. A third device applied a horizontal force near the center of mass, which impedes or aids forward progression thus overloading or unloading the plantarflexor muscles. We found that when demand was decreased in the muscles measured, the PTS significantly increased. Conversely, when muscle demand was increased in the plantar flexors, the PTS decreased. However, combining assistive devices did not produce an even faster PTS. We conclude that altering the demand on specific muscles can change the preferred walk-run transition speed. However, the lack of a summation effect with multiple external devices, suggests that another underlying factor ultimately determines the preferred walk-run transition speed.