Fitness News You Can Use

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Exercise ETC’s Review of Exercise Related Research
Compiled by Jeannie Patton, MS, CSCS

Ninety degree seat angle on leg extension optimal for vastus muscle recruitment

One of the most common exercises performed in the gym is the leg extension, which involves extension of the knee joint from a flexed position while seated. The purpose of this study was to examine the electrical activity of the superficial quadriceps muscles and the erector spinae at 3 different seat angles during the leg extension exercise.

Twenty young healthy men and women with a minimum of 6 months of weightlifting experience served as subjects. The 3 angles tested were 90 degrees, 100 degrees, and 110 degrees. The researchers found the greatest activity for the erector spinae occurred at a seat angle of 110 degrees. The best recruitment of both the vastus lateralis and medialis occurred at a seat angle of 90 degrees.

Since the goal of the leg extension is to maximize the recruitment of the quadriceps muscle while minimizing the stress to the low back, the results of this study would support a seat angle of 90 degrees to accomplish that goal.

Gomez, Thelma, R. et al. The Impact of Seatback Angle on Electromyographical Activity of the Lower Back and Quadriceps Muscles During Bilateral Knee Extensions. Journal of Strength and Conditioning Research. 2005, 19(4), 908-917.


Heavy squats prior to sprinting shown to improve performance

Post-activation potential (PAP) is defined as an increase in the contractile ability of muscle after a bout of previous contractions. The purpose of this study was to determine whether performing high force or explosive force movements prior to sprinting would improve running speed.

Fifteen NCAA Division III football players served as subjects. The heavy loaded squat protocol consisted of 1 set of 3 repetitions at 90% of the athleteÂ’s 1 repetition max (1RM). The loaded jump consisted of a squat jump with a load of 30% of the 1RM from a squat performed on a modified Smith machine.

The results of the study indicated that 40-meter sprint time statistically improved following the heavy loaded squat protocol but not the vertical jump protocol. Based on this study, Fitness Professionals should consider different types of warm-ups for athletes involved in activities that require a single bout of maximal running speed. Other types of warm-ups such as stretching and jogging have been shown to decrease performance. Based on the results of this investigation, heavy squats performed 4 minutes prior to a 40-meter sprint can improve performance.

McBride, Jeffrey. Et al. The Acute Effects of Heavy-Load Squats and Loaded Countermovement Jumps on Sprint Performance. Journal of Strength and Conditioning Research. 2005, 19(4), 893-897


Intermittent cardio exercise results in slightly higher caloric burn than continuous exercise

It is recommended that every adult accumulate 30 min or more of moderate intensity physical activity on most, if not all, days of the week. The purpose of this study was to compare energy expenditure during and following continuous exercise versus intermittent exercise.

Twenty fit college-aged males served as subjects. Energy expenditure was measured at rest, during exercise and during recovery. Subjects performed 30 minutes of continuous exercise, which included a 45-minute recovery period, and on a separate testing day three 10-minute bouts which included 15 minutes of recovery following each bout. Workload was adjusted during exercise in both test protocols to maintain oxygen consumption at 70% VO2max.

Results indicated that total energy expenditure during 30 min of intermittent exercise and three 15-minute recovery periods was slightly greater than the collective energy expenditure for 30 continuous minutes of exercise and 45 minutes of recovery. The 30 minutes of continuous exercise actually had a slightly higher energy expenditure (7 Kcals), but the three 15 minute recovery periods from the intermittent exercise produced a higher energy expenditure (22.2 Kcals) accounting for the 15 Kcal difference between the protocols.

The results of this study from a practical standpoint indicate that intermittent bouts of moderate exercise result in the same energy expenditure as continuous exercise at the same intensity. Since time is the number one reason why many individuals do not exercise, Fitness Professionals should share these results with their clients and the general public. If caloric expenditure is the primary goal, then performing numerous bouts of exercise throughout the day will burn slightly more calories than
performing one continuous bout. Smaller time segments may also be more convenient and thus increase motivation and adherence.

Darling JL, Linderman JK, Laubach LL. Energy expenditure of Continuous and Intermittent Exercise in College aged males. Journal of Exercise Physiology online 2005;8(4):1-8.


Increasing the volume of exercise can result in improvements in oxygen consumption

Exercise to increase aerobic fitness is routinely done by Fitness Professionals, however very few studies exist that examined the effects of different intensity and amount of exercise on peak oxygen consumption. The purpose of this study was to determine the effects of intensity and amount of exercise on improvements in peak oxygen consumption.

One hundred and thirty-three sedentary, overweight men and women served as subjects. Subjects were assigned to one of four groups:

• High-amount/high–intensity (65%-80% of VO2, equivalent of jogging 20 miles/week)
• Low-amount/high-intensity (65%-80% of VO2, equivalent of jogging/walking on an incline12 miles/week)
• Low-amount/moderate-intensity (40%-55% of VO2, equivalent of walking 12
miles/week)
• Non-exercising control group

All exercise groups experienced an increase in peak oxygen consumption and time to exhaustion compared to the controls. The high-intensity/high amount group showed the greatest improvement in peak VO2. The results also indicated that increasing the intensity from 40%-55% to 65%-80% with a controlled amount of exercise (equivalent of 12 miles/week) did not significantly improve peak oxygen consumption. However increasing the amount of exercise did produce improvements.

Fitness Professionals need to consider a number of factors when programming for clients. Based on the results of this study, by increasing the amount of exercise performed, one can achieve similar improvements in oxygen consumption while working at moderate intensities. Higher intensities may not be appropriate for those with health issues and may also be perceived as uncomfortable by others, and thus affect adherence and motivation.

Duscha, Brian, D. et al. Effects of Exercise Training Amount and Intensity on Peak Oxygen Consumption in Middle-Age Men and Women at Risk for Cardiovascular Disease. CHEST. October, 2005; 128:2788-2793.