Monthly Archives: October 2018

Bodyweight exercise list

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Abdominals
Plank Ups: Start in high plank. Bend one arm to bring your elbow and your forearm to the floor. Bring the other arm down so you are in a forearm plank. Push back up to the start position, placing each hand where your elbows were.
Plank Taps: Start in high plank with your feet hip-distance apart. Then tap your left hand to your right shoulder while engaging your core and glutes to keep your hips as still as possible.
Lateral Plank Walks: Start in high plank. Step your right foot and your right hand to right side immediately following with your left foot and your left hand.
Plank Star Jumps: Start in high plank. Keeping your core engaged, jump your feet out wide and back in (like star jumps).
Plank with lifting right arm and left leg, then lifting left arm and right leg.
Plank with arm lifts to the side (90 degrees with the body) without turning torso.
Plank high knee run: in plank, alternately bring one knee to chest, then the other.
Plank knee to same shoulder: in plank, alternately bring left knee to left shoulder, return to plank, bring right knee to right shoulder.
Crocodile walk: from plank, step left foot close to left hand, left knee is close to left shoulder. Step right hand forward. Then step left hand and right foot forward, so the right knee is close to right shoulder. Repeat with right hand and left knee. Stay low, with bent elbows and one knee bent.
Plank knee to opposite elbow or shoulder: in plank, alternately bring one knee under the body to the opposite armpit, return to start, then the other knee to the opposite armpit. Intensification: straighten the leg that crosses under the body, without touching the leg to the ground.
Plank or tabletop side leg lifts: similar to plank knee to shoulder, but straight leg lifted to the side.
Bear pose: from tabletop pose (hands and knees on the ground), lift knees slightly off the ground, so you are standing on hands and toes, with hips and knees bent at 90 degrees.
Crunches: lying on your back, knees and hips bent, feet on the ground, lift torso toward knees, return.
Leg lifts on your back: lying on your back, lift both straight legs without arching the back (lower back stays on the ground). Then lower the legs back down. Repeat.
Supine leg rotations: lying on your back, lift straight legs 30 degrees off the ground, make circles with the legs, keeping the legs together and straight. Lower back stays on the ground, no arching of the back.
Jackknife: lying on your back, arms overhead, bend at the hips to lift both straight arms and straight legs, touch fingers to toes.
Windshield wiper: lying on your back, hips bent 90 degrees, feet touching, keep both shoulders on the ground and rotate from the waist to move both feet to one side to touch the ground, then lift back up. Repeat on the other side.

Chest/pectorals
Push-Ups or clapping push-ups.
One-arm push-ups.
Handstand push-ups.
Push-up into side plank, then back to push-up, then side plank on the other side.
Staggered push-ups: push-ups with one arm placed more forward than the other.
Burpees/ squat thrusts: do a push-up, then jump legs close to hands, then jump up, return to low squat, put hands on the floor, jump legs back to plank. Repeat.

Calves
Calf raises: Stand on one leg, rise up on your toes, return down.

Hamstrings
Low plank or chaturanga leg lifts. Start with hands (or elbows) and feet on the ground, body straight, elbows bent 90 degrees. Lift one leg toward the sky. The leg may be straight or bent. Do not rotate the foot outward, but keep pointing the toes in and up. Keep abdomen tense to lessen the use of the back muscles, focus on lifting with the hamstring instead.
Isometric heel press: stand on one foot, bend the other knee 90 degrees and press the heel up against the hand, keeping the hips straight. Tense the abdominals to discourage using the lower back muscles. Use the hamstring instead.

Quads, glutes, sides of hips
Squats or squat jumps, or one-legged squats.
Forward-backward squat jumps: from a squat, jump forward into a squat, then back to starting position.
Wide-legged squats or wide-legged squat jumps.
Lunges, perhaps adding a front kick after standing up from each lunge.
Lunge jumps: start on left foot and right toes, with the left hip, knee and ankle bent 90 degrees, the right hip straight and the right knee and ankle bent 90 degrees. Jump into the same position on the opposite side: right hip, knee and ankle bent 90 degrees, left hip straight, the left knee and ankle bent 90 degrees.
Lateral lunges: from standing, step wide to the left, bending the left knee, keeping the right leg straight. Step back to standing. May add a leg raise to the side after each lunge.
Curtsy Lunges: from standing, cross one leg in front of the other and do a squat.

Back
Superman: lying on your belly, straight arms pointing above head, lift both arms and straight legs. Keep the legs together.
Locust: lying on your belly, straight arms behind back, fingers interlocked, lift torso and straight legs.
Airplane: lying on your belly, straight arms in a T position to body, lift both arms and both legs. Keep the legs together and straight.
Prone snow angel: lying on your stomach, lift both arms, move straight arms from pointing toward feet to pointing above head, then back toward feet (from locust to airplane to superman pose, then back to airplane and to locust).
Forward bend/ good morning: from standing, bend forward at the hips with a straight back and straight legs, fingers interlocked behind the head. Then stand tall again. Intensification: keep straight arms overhead (in one line with the back) the whole time.
Bridge/ hip raise, or one-legged bridge. In one-legged bridge, the other leg can be straight or bent, parallel to ground or pointing to the sky.
Upward plank: facing the sky, support your weight on hands and heels. Keep arms, legs and body straight, with legs and body forming one line.
Upward plank leg raises: from upward plank, raise one leg from the hip, keeping the knee straight. The other leg and the body still form a straight line.
Ant walk/ crab walk: facing the sky, walk on your hands and feet, knees bent about 90 degrees, elbows almost straight. Keep your hips and back straight.

Obliques/side muscles
Side bend: stand straight, arms straight overhead, elbows straight, fingers interlocked, biceps squeezing the ears. Bend to one side, then stand tall again. To focus on the side muscles, not lower back or abdomen, bend exactly to the side, not forward or back.
Side Plank. Intensification: lift upper leg, perhaps grab toe of upper leg.

Shoulders
Dive bomber/ Hindu push-up/ Downdog-to-chaturanga and return to downdog. Start with hands and toes on the ground, hips bent 90 degrees, legs and arms straight, arms in one line with the back. Bend elbows and move chest between hands until the hips are straight (body and legs form one line) and chest hovers a few cm above ground. Then return to start.
Downdog push-ups/ inverted shoulder press/ pike press. Start with hands and toes on the ground, hips bent 90 degrees, legs and arms straight, arms in one line with the back. Bend elbows so head approaches floor between the hands. Keep hips at 90 degrees, back and neck in one line. Push back to starting position.
Arm circles: standing, straight arms in T position (straight line through both arms), make as small and fast circles with the arms as possible.

Triceps
Narrow push-up: hands close to each other on the ground, elbows brushing sides of torso.
Diamond Push-Up: thumbs and forefingers form a triangle.
Triceps Dip, or one-arm triceps dip: Sit on the ground with your legs in front and your back close to a chair, box or step. Place your palms on the box behind you, fingers facing toward your body. Straighten your arms to lift your legs and butt off the ground, then bend your elbows to lower back down (without letting your butt touch the ground). Keep your heels on the ground, elbows directly behind your body.
Reverse push-up: face the sky, hands and heels on the ground, body and legs in one straight line. Bend the elbows, then push back up until the elbows are straight again. Keep the body and legs straight while doing this.
Back-to-wall push-aways: stand with your back against a wall, feet away from the wall, body and legs in one straight line. Push away from the wall using your elbows or hands.

Warm-ups
Knee lift run on the spot.
Butt kick run, hips straight.
Forward kicks/ can-can, or forward kicks with jumps.
Scissor stepping to the side: from standing, cross left leg in front of the right, then step right leg to the right so the legs are not crossed any more. Then cross the left leg behind the right, then step the right leg to the right. Repeat. Then switch sides.
Forward sprint.
Backward run.
Gallop to the side: one leg steps wide to the side, then the other hops to meet it. Repeat. Then switch sides
Hop on one foot, forward and backward.

The motivation for this list was my inability to find a good ad-free list of bodyweight exercises online. By bodyweight I mean exercises that do not require rubber bands, a chin-up bar, weights or other equipment. Preferably the exercises would only require a floor, not even a wall or a chair, but I included some exercises above that do require these.

Heating my apartment with a gas stove

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There is no built-in heating system in my Australian-standard un-insulated apartment, and the plug-in electric radiators do not have enough power to raise the temperature by a degree. In the past two winters, I used the gas stove as a heater. It is generally unwise to heat an enclosed space without purpose-built ventilation (such as a chimney) by burning something, because of the risk of CO poisoning. Even before CO becomes a problem, suffocation may occur because the CO2 concentration rises and oxygen concentration falls. Therefore, before deciding to heat with a gas stove, I looked up the research, made thorough calculations and checked them several times. I also bought a CO detector, tested it and placed it next to the gas stove. The ceiling has a smoke alarm permanently attached, but this only detects soot in the air, not gases like CO.
For the calculations, I looked up how much heat is produced by burning a cubic metre or kilogram of CH4 (natural gas), how much the temperature of the air in the apartment should rise as a result, how much CO2 the burning produces, and what the safe limits of long-term CO2 exposure are.
The energy content of CH4 is 37.2 MJ/m3, equivalently 50-55.5 MJ/kg. A pilot light of a water heater is estimated to produce 5.3 kWh/day = 20 MJ/day of heat, but a gas stove’s biggest burner turned fully on is estimated to produce 5-15 MJ/h, depending on the stove and the data source.
The chemical reaction of burning natural gas when oxygen is not a limiting factor is CH4 +2*O2 =CO2 +2*H2O. The molar masses of these gases are CH4=16 g/mol, O2=32 g/mol, CO2=44 g/mol, H2O=18 g/mol, air 29 g/mol. One stove burner on full for 1 hour uses about 0.182 kg =0.255 m3 of CH4 and 0.364 kg of O2, which depletes 1.82 kg = 1.52 m3 of air. The burning produces 2.75*0.182 = 0.5 kg = 0.41 m3 of CO2. The CO2 is denser than air, which is why it may remain in the apartment and displace air when the cracks around the windows are relatively high up. On the other hand, the CO2 also mixes with the air, so may escape at the same rate. Or alternatively, the CO2 is hot, so may rise and escape faster than air. For safety calculations, I want to use a conservative estimate, so assume that the CO2 remains in the apartment.
The volume of the apartment is 6x5x2.5 m =75 m^3. The density of air at room temperature is 1.2 kg/m^3, thus the mass of air in the apartment is 90 kg. The specific heat of air is 1005 kJ/(kg*K) at 20C. The walls and ceiling leak heat, thus more energy is actually needed to heat the apartment by a given amount than the calculation using only air shows. It takes 900 kJ of heat to raise the temperature of the air, not the walls, by 10C (from 12C to 22C). This requires 9/555 kg = 9/(16*555) kmol of CH4 with estimated energy density 55500 kJ/kg. Burning that CH4 also takes 9/(8*555) kmol of O2 and produces 9*11/(4*555) kmol = 9/200 kg of CO2.
The normal concentration of CO2 in outside air is 350-450 ppm. Estimate the baseline concentration in inside air to be 1/2000 ppm because of breathing and poor ventilation. Adding 1/2000 ppm from heating, the CO2 concentration reaches 1/1000 ppm. This is below the legal limit for long-term exposure.
CO is produced in low-oxygen burning. As long as the CO2 concentration in the air is low and the oxygen concentration high, the risk of CO poisoning is small.
For the actual heating, I first tested running the smallest burner all day while I was at home, and paid attention to whether I felt sleepy and whether the air in the apartment smelled more stale than outside or in the corridor. There seemed to be no problems. For nighttime heating, I started with the smallest burner in the lowest setting, similarly paying attention to whether the air in the morning smelled staler than usual and whether I felt any different. Because there were no problems, I gradually increased the heating from week to week. The maximum I reached was to turn on the largest burner to less than half power, and one or two smaller burners fully. Together, these burners produced much less heat than the largest burner on full, as could be easily checked by feel when standing next to the stove. At night, the stove prevented the temperature in the apartment from dropping by the usual 2C, but did not increase it. The CO2 produced was probably far less than the bound I calculated above by assuming a 10C increase in temperature. Empirically, I’m still alive after two winters of letting the gas stove run overnight.

Charge electric cars fast by changing the battery

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An electric car drives into a charging station. The driver pushes a button to unlock the battery compartment hatch on the rear bumper. The hatch springs open, which is detected by a camera of the station. A robotic arm swings into motion and, guided by cameras, radar or ultrasound, latches on to well-marked standardised handles on the rear of the battery. The arm pulls out the 300kg, 1×2 metre battery from underneath the floor of the car and slides it onto a conveyor belt. The belt moves the battery to one side and brings up a new battery, which the robotic arm picks up and slides back into the car’s battery compartment. The driver pushes a button to close and lock the battery compartment and drives off. The whole charging process takes less than a minute – significantly faster than filling up a gasoline-powered car.
Due to the weight and size of an electric car’s battery, a robotic arm is probably necessary. It is also faster and more precise than a human.
The usage history of the battery should be recorded securely, in order to make users pay for its depreciation, not just the electricity they used. Blockchain may be useful for keeping track of usage, which is needed to deter the moral hazard of using the battery inappropriately and not paying for the damage, or swapping it for a cheaper alternative before having it changed back to a standard one in a charging station.
The compartment in which the battery is has to be water-tight and locked (like the trunk or hood of a car) to prevent theft. The compartment should also be unlockable remotely by the owner or other authorised person, in case the car is self-driving and has no humans in it.

Improvement for noise-cancelling headphones

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Current noise-cancelling headphones deal well with predictable noise that has a short period of repetition, for example engine rumbling or the hum of an air-conditioner or fan. Unpredictable noise is of course difficult to cancel – the headphones would have to detect the new sound and produce the opposite wave of air pressure quicker than the human ear can detect the new sound. This is theoretically possible, because the sound reaches the outside of the headphone before it reaches the inside of the ear, but may not be feasible at the current technology level.
What is possible, but not done, at least by the Sony MDR-1000x headphones I have, is cancelling predictable noise with a longer period of repetition. Specifically, the beeping sound of trucks reversing has a period of 1-2s and is very predictable, but the headphones do not cancel it at all. It seems that a tweak of the noise-prediction algorithm could fix this – no need to invoke machine learning or anything more complicated. The headphones would just have to keep track of the sounds reaching them in the last few seconds and look for simple repeating patterns. Then these patterns can be predicted and cancelled. Currently the headphones seem to predict only based on the last half-second or less, so any longer repetitions of sound are not taken into account.
Some birdsong is repeated beeping, similar to the signal of trucks reversing, but of course slightly less predictable. This bird-noise could conceivably also be cancelled, although if the gaps between the beeps vary, then the first small length of time during an unexpectedly early beep would be difficult. Similarly, if the length of the beeps varies, then a beep that stops unexpectedly early would be over-cancelled (headphones produce a sound that is detectable on the background of silence).
To help the headphones recognise new noise patterns, the user can press a button when an undesirable sound is heard, and release the button when the sound stops. The algorithm can compare the button presses to its sound-recording in the same time interval, which would help it identify the start and end of the noise that needs to be cancelled. Sometimes humans are better at detecting complex patterns than a computer, in which case this user input to the headphones would speed up the identification of new forms of noise.

Online reviews should include more facts

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Online reviews are a public good and increase social welfare, but they could be improved by including more concrete data. For example, a restaurant or grocery store review should list the prices of specific foods. A review of a bar or function venue could estimate the number of tables and seats and the distance between tables, thus quantifying how cramped the room is. Currently, most reviews on Google Maps, Yelp and other similar sites are vague, just stating that the reviewer had a bad or great experience, that the staff were helpful or not, etc.
The purpose of a review is (hopefully) to help others (although some people just write rants to vent their emotions). Facts in reviews would help others more than opinions. Photos of the establishment and the food are useful, because they provide factual information. Some photos are more helpful than others. For example, it is more useful to see the inside than the outside of a venue. It is not very useful to see a picture of the outdoor sign of the establishment, but a readable photo of the menu conveys lots of information. In the future, Google Maps and competitors could automatically extract text from photos that contain it, and display the information in search results. Then photos of the menu, or of prices in a grocery store would be even more useful.
The idea for this post came from fruitlessly searching the web for current prices of groceries in different supermarkets in town. It would have been helpful if recent reviews of these supermarkets had included prices of at least some items.
The grocery price comparison apps that I tried had the limitation that the prices were for specific branded products and per package (e.g. Organic Carrots 500g), not per kilogram of a generic product (e.g. 1kg of carrots). This made it difficult to compare general pricing across shops, because each shop has a different range of brands, and only the price of the exact same brand can be compared.
An easy fix to improve the apps would be to allow users to specify which differently-branded products should be treated as identical, for example “Coles orange juice 2 litres” is the same for me as “Woolworths orange juice 2 litres”. Merging similar products would also reduce the memory requirement of the app, because the product database would have fewer entries to keep track of.