Why could this be?
Rachel Straub, PhD, is an exercise physiologist and co-author Weight training without injury: Over 350 step-by-step pictures with what not to do!Explains that strength improvements from resistance training come from both increased neural adaptations and increased muscle size (hypertrophy).
“During the early stages of strength training (the first month), strength improvements are primarily due to improvements in neural drive, as hypertrophy does not become a dominant contributor until weeks three to five,” says Dr. Straub. Since this study only lasted four weeks, it is likely that the gains seen were mainly due to neural adaptation.
These adaptations are what allow your brain to recruit more muscle fibers in a coordinated, efficient fashion, resulting in stronger muscle contractions. “More frequent sessions provide more frequent nerve stimulation with adequate rest,” says Dr. Straub. And when the brain receives a stimulus more often, changes occur more easily.
Short strength training workouts per day instead of one or two long workouts per week also provide other benefits. “If you strength train only once a week, fatigue limits your performance and there is a long delay in the training stimulus,” explains Dr. Straub. “However, if you strength train every day, you can change your focus (eg lower body one day versus upper body another day), so fatigue becomes less of a limiting factor.”
So what should your weekly routine look like?
With this in mind, if you’re going to aim for regular strength training workouts, skip full-body sessions and zeros on a specific body part each day to give your muscles enough rest. (Generally speaking, you should take 48 to 72 hours between workouts that target the same muscle groups.)
“The American College of Sports Medicine recommends split-body workouts for advanced strength training, defined as four to five days per week,” notes Dr. Straub. “If you strength train less frequently (two to three days a week) then a total-body workout is best.”
For the upper body, Dr. Straub recommends training the biceps, triceps, back, chest, and shoulders. On lower-body days, he recommends focusing on the hamstrings, quadriceps, and glutes. “The core can be included on both days or any day,” he adds.
When determining the load you use and the number of repetitions you should do for each exercise, Dr. Straub says you need to consider your primary goal. For example, doing very few repetitions at maximum eccentric strength is ideal for increasing muscle strength and size. But if your goal is to increase muscular endurance, focus on using high reps (more than 15) and light loads with very little rest. Either way, she says, “If the last one to three reps of a set aren’t challenging, the load is too light.”
Here’s an example of how you might structure a week’s worth of mini strength training workouts: